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111-500: The Oxford–AstraZeneca COVID‑19 vaccine , sold under the brand names Covishield and Vaxzevria among others, is a viral vector vaccine for the prevention of COVID-19 . It was developed in the United Kingdom by Oxford University and British-Swedish company AstraZeneca , using as a vector the modified chimpanzee adenovirus ChAdOx1 . The vaccine is given by intramuscular injection . Studies carried out in 2020 showed that

222-570: A booster (third) dose given at least six months later produces a strong immune response. A booster dose may not be necessary, but it alleviates concerns that the body would develop immunity to the vaccine's viral vector, which would reduce the potency of annual inoculations. On 22 March 2021, AstraZeneca released interim results from the phase III trial conducted in the US that showed efficacy of 79% at preventing symptomatic COVID-19 and 100% efficacy at preventing severe disease and hospitalisation. The next day,

333-718: A booster dose of the Pfizer–BioNTech or the Moderna vaccine is initially about 60% effective against symptomatic disease caused by Omicron, then after 10 weeks the effectiveness drops to about 35% with the Pfizer–BioNTech and to about 45% with the Moderna vaccine. The vaccine remains effective against severe disease, hospitalization and death. The Oxford–AstraZeneca COVID-19 vaccine should not be administered to people who have had capillary leak syndrome . The most common side effects in

444-648: A company Christmas party held at a restaurant in Norway's capital, Oslo , were infected with the Omicron variant. France has confirmed only 25 cases of the new Omicron variant but officials say the number could jump significantly in the coming weeks. By 6 December, Malaysia confirmed its first case of the variant. The case was a South African student entering to study at a private university. In Namibia, 18 cases out of 19 positive COVID-19 samples that had been collected between 11 and 26 November were found to be Omicron, indicating

555-643: A company based in Europe, instead of Merck & Co. , a US-based company ( The Guardian reported the initial partner was the German-based Merck Group instead). Government ministers also had concerns that a vaccine manufactured in the US would not be available in the UK, according to anonymous sources in The Wall Street Journal . Financial considerations at Oxford and spin-out companies may have also played

666-790: A few variants, but not in Delta which dominated in the country in October) and by a sudden increase of COVID-19 cases in Gauteng; sequencing revealed that more than 70 percent of samples collected in the province between 14 and 23 November were a new variant. The first confirmed specimens of Omicron were collected on 8 November 2021, in South Africa and on 9 November, in Botswana. Likely Omicron (SGTF) samples had occurred on 4 November 2021 in Pretoria, South Africa. When

777-713: A final decision and to establish an expert group to provide a broader assessment on the safety of the AstraZeneca and Janssen vaccines. In May, the expert committee also recommended suspending the use of both vaccines. Finally, in May —two months after the initial suspension— the Prime Minister of Norway announced that the government decided to completely remove the AstraZeneca vaccine from the Norwegian Coronavirus Immunisation Programme, and people who have had

888-642: A good safety profile, with side effects including injection-site pain, headache, and nausea, all generally resolving within a few days. More rarely, anaphylaxis may occur; the UK Medicines and Healthcare products Regulatory Agency (MHRA) has 268 reports out of some 21.2   million vaccinations as of 14 April 2021. In very rare cases (around 1 in 100,000 people), the vaccine has been associated with an increased risk of blood clots when in combination with low levels of blood platelets ( embolic and thrombotic events after COVID-19 vaccination ). According to

999-524: A high level of prevalence in the country. Fiji also confirmed two positive cases of the variant. They travelled from Nigeria arriving in Fiji on 25 November. On 9 December, Richard Mihigo, coordinator of the World Health Organisation's Immunisation and Vaccine Development Programme for Africa, announced that Africa accounted for 46% of reported cases of the Omicron variant globally. On 13 December,

1110-677: A lack of familiarity with the Greek alphabet, and the relative frequency of the Latin prefix " omni " in other common speech. The GISAID project has assigned it the clade identifier GR/484A, and the Nextstrain project has assigned it the clade identifiers 21K and 21L, both belonging to a larger Omicron group 21M. Omicron was first detected on 22 November 2021 in laboratories in Botswana and South Africa based on samples collected on 11–16 November, with

1221-490: A longer interval usually allows time for the immune system's response to mature. As of June 2022, Omicron had about 50 mutations relative to the Wuhan-Hu-1 or B variant, which is more than any previous SARS-CoV-2 variant . Thirty-two of these pertained to the spike protein, which most vaccines target to neutralise the virus. As of December 2021, many mutations were novel and not found in previous variants. As of April 2022

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1332-448: A modified version could be ready for mass production in 45 days. Sinovac said it could quickly mass-produce an inactivated vaccine against the variant and that it was monitoring studies and collecting samples of the variant to determine if a new vaccine is needed. On 7 December 2021, at a symposium in Brazil with its partner Instituto Butantan , Sinovac said it would update its vaccine to

1443-400: A new multi-country trial using the lower dose, which had led to the 90% claim. The full publication of the interim results from four ongoing Phase III trials on 8 December allowed regulators and scientists to begin evaluating the vaccine's efficacy. The December report showed that at 21 days after the second dose and beyond, there were no hospitalisations or severe disease in those who received

1554-406: A nucleic acid coding for a specific protein to a cell, the vaccines employ a variant of a virus as its vector. This process helps to create immunity against the disease, which helps to protect people from contracting the infection. Viral vector vaccines do not cause infection with either the virus used as the vector or the source of the antigen. The genetic material it delivers does not integrate into

1665-407: A part in the decision to partner with AstraZeneca. An initially not-for-profit licensing agreement was signed between the university and AstraZeneca PLC, in May 2020, with 1   billion doses of potential supply secured, with the UK reserving access to the initial 100   million doses. Furthermore, the US reserved 300   million doses, as well as the authority to perform Phase III trials in

1776-504: A partial lockdown on 20 December 2021, ordering the closure of all bars, casinos, gyms, schools, and theatres, as well as imposing restrictions on the capacity and operating hours of restaurants, and the prohibition of spectators at professional sporting events. On 18 December 2021, the Netherlands government announced a lockdown intended to prevent spread of the variant during the holiday period. In December 2021, some countries shortened

1887-404: A person's genome . The majority of viral vectors lack the required genes, making them unable to replicate. In order to be widely accepted and approved for medical use, the development of viral vector vaccines requires a high biological safety level. Consequently, non or low-pathogenic viruses are often selected. Viral vector vaccines have benefits over other forms of vaccinations depending on

1998-473: A potential Omicron spike, although no cases had yet been detected in the state or the rest of the United States. On 27 November 2021, Switzerland introduced obligatory tests and quarantine for all visitors arriving from countries where the variant was detected, which originally included Belgium and Israel. On 26 November 2021, South African Minister of Health Joe Phaahla defended his country's handling of

2109-591: A press release that a recommendation could be issued by the agency by 29 January, followed by the European Commission deciding on a conditional marketing authorisation within days. On 29 January 2021, the EMA recommended granting a conditional marketing authorisation for AZD1222 for people 18 years of age and older, and the recommendation was accepted by the European Commission the same day. Prior to approval across

2220-562: A publicly available database, such as GISAID , report initial cases/clusters associated with virus-of-concern infection to the WHO through the International Health Regulations (IHR) mechanism, where capacity exists and in coordination with the international community, perform field investigations and laboratory assessments to improve understanding of the potential impacts of the virus of concern on COVID-19 epidemiology, severity, and

2331-467: A re-analysis because of doubts, the team retracted the article on 20 December 2022, due to contamination of the samples. On 24 November 2021, the variant was first reported to the WHO from South Africa based on samples that had been collected from 14 to 16 November. South African scientists were first alerted by samples from the very beginning of November where the PCR tests had S gene target failure (occurs in

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2442-527: A reduction in the threat to public health, the WHO stopped classifying Omicron as a variant of concern in order to maintain this classification only for new threats. Instead, the WHO classified its subvariants as variants of interest and under monitoring. On 26 November 2021, BioNTech said it would know in two weeks whether the current vaccine is effective against the variant and that an updated vaccine could be shipped in 100 days if necessary. AstraZeneca , Moderna and Johnson & Johnson were also studying

2553-418: A review of efficacy and safety data on 27 November 2020, followed by approval for use on 30 December 2020, becoming the second vaccine approved for use in the national vaccination programme . The BBC reported that the first person to receive the vaccine outside of clinical trials was vaccinated on 4 January 2021. The European Medicines Agency (EMA) began review of the vaccine on 12 January 2021, and stated in

2664-702: A single suspected case in Germany. On 27 November, two cases were detected in the United Kingdom, another two in Munich , Germany and one in Milan , Italy. On 28 November 13 cases were confirmed in the Netherlands among the 624 airline passengers who arrived from South Africa on 26 November. Confirmation of a further 5 cases among these passengers followed later. Entry into the Netherlands generally required having been vaccinated or PCR-tested, or having recovered. The passengers of these two flights had been tested upon arrival because of

2775-485: A small and predictable proportion. After the WHO announcement, on the same day, several countries announced travel bans from southern Africa in response to the identification of the variant, including the United States , which banned travel from eight African countries, although as of 30 November 2021 it notably did not ban travel from any European countries, Israel, Canada, or Australia where cases were also detected at

2886-406: A smallpox vaccine. The Ebola vaccine regimen approved by the European Commission was developed by Janssen Pharmaceutials and Bavarian Nordic , and utilizes MVA technology in its second vaccine dose of Mvabea (MVA-BN-Filo). Vesicular stomatitis virus (VSV) was introduced as a vaccine vector in the late 1990s. In most VSV vaccine vectors, attenuation provides safety against its virulence. VSV

2997-468: A soccer club. Sweden also confirmed their first case on 29 November, as did Spain, when a traveler came from South Africa. On 30 November, the Netherlands reported that Omicron cases had been detected in two samples dating back as early as 19 November. A positive case was recorded in Sydney from a traveller who had visited southern Africa before travel restrictions were imposed, and was subsequently active in

3108-442: A third booster dose is needed to prevent severe disease in healthy adults. Preliminary data from a study in Brazil with 61 million individuals from January to June 2021, indicate that the effectiveness against infection, hospitalization and death is similar between most age groups, but protection against all these outcomes is significantly reduced in those aged 90 year of age or older, attributable to immunosenescence . A vaccine

3219-445: A warning in the product information. Additional side effects include tinnitus (persistent ringing in the ears), paraesthesia (unusual feeling in the skin, such as tingling or a crawling sensation), and hypoaesthesia (decreased feeling or sensitivity, especially in the skin). The Oxford–AstraZeneca COVID-19 vaccine is a viral vector vaccine containing a modified, replication-deficient chimpanzee adenovirus ChAdOx1 , containing

3330-402: Is administered by two 0.5 ml (0.017 US fl oz) doses given by intramuscular injection into the deltoid muscle (upper arm). The initial course consists of two doses with an interval of 4 to 12 weeks between doses. The World Health Organization (WHO) recommends an interval of 8 to 12 weeks between doses for optimal efficacy. As of August 2021, there is no evidence that

3441-558: Is an RNA virus and is part of the Rhabdoviridae family. The VSV genome encodes for nucleocapsid, phosphoprotein, matrix, glycoprotein, and an RNA-dependent RNA polymerase proteins. The rVSV-ZEBOV vaccine , known as Ervebo , was approved as a prophylactic Ebola vaccine for medical use by the FDA in 2019. The vaccine is a recombinant , replication-competent vaccine consisting of genetically engineered vesicular stomatitis virus. The gene for

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3552-544: Is found in Europe, and in 25 states in the United States of America, including three cases in California. Three doses of a COVID-19 vaccine provide protection against severe disease and hospitalisation caused by Omicron and its subvariants. For three-dose vaccinated individuals, the BA.4 and BA.5 variants are more infectious than previous subvariants but there is no evidence of greater sickness or severity. On 26 November 2021,

3663-529: Is generally considered effective if the estimate is ≥50% with a >30% lower limit of the 95% confidence interval . Effectiveness is generally expected to slowly decrease over time. Preliminary data suggest that the initial two-dose regimen is not effective against symptomatic disease caused by the Omicron variant from the 15th week onwards. A regimen of two doses of the Oxford–AstraZeneca vaccine followed by

3774-434: Is part of the poxvirus family. It is a large, complex, and enveloped virus that was previously used for the smallpox vaccine. The vaccinia virus's large size allows for a high potential for foreign gene insertion. Several vaccinia virus strains have been developed including replication-competent and replication-deficient strains. Modified vaccinia ankara (MVA) is a replication-deficient strain that has been safely used for

3885-484: The Danish Health Authority suspended use of the vaccine. The Danish Health Authority said that it had other vaccines available, and that the next target groups being a lower-risk population had to be "[weighed] against the fact that we now have a known risk of severe adverse effects from vaccination with AstraZeneca, even if the risk in absolute terms is slight." A 2021 study found that the decisions to suspend

3996-696: The European Medicines Agency (EMA), and the Australian Therapeutic Goods Administration (provisional approval in February 2021), and was approved for an Emergency Use Listing by the World Health Organization (WHO). More than 3   billion doses of the vaccine were supplied to countries worldwide. Some countries have limited its use to elderly people at higher risk for severe COVID-19 illness due to concerns over

4107-583: The European Medicines Agency , as of 4 April 2021, a total of 222 cases of blood clots had been recorded among 34 million people who had been vaccinated in the European Economic Area (a percentage of 0.0007%). On 30 December 2020, the vaccine was first approved for use in the UK vaccination programme , and the first vaccination outside of a trial was administered on 4 January 2021. The vaccine has since been approved by several medicine agencies worldwide, such as

4218-555: The Food and Drug Administration surrounding a patient illness that triggered a clinical hold, according to the US Department of Health and Human Services (HHS) Secretary Alex Azar . The results of the COV002 phase II/III trial showed that immunity lasts for at least one year after a single dose. On 23 November 2020, the first interim data was released by Oxford University and AstraZeneca from

4329-465: The National Institute of Allergy and Infectious Diseases (NIAID) published a statement countering that those results may have relied on "outdated information" that may have provided an incomplete view of the efficacy data. AstraZeneca later revised its efficacy claim to be 76% after further review of the data. On 29 September 2021, AstraZeneca shows of 74% efficacy rate in the US trial. A study on

4440-536: The Serum Institute of India at Pune . The Halix site at Leiden was approved by the EMA on 26 March 2021, joining three other sites approved by the EU. The vaccine arose from a collaboration between Oxford University's Jenner Institute and Vaccitech , a private company spun off from the university, with financing from Oxford Sciences Innovation , Google Ventures , and Sequoia Capital , among others. The first batch of

4551-602: The WHO 's Technical Advisory Group on SARS-CoV-2 Virus Evolution declared PANGO lineage B.1.1.529 a variant of concern and designated it with the Greek letter omicron . The WHO skipped the preceding letters nu and xi in the Greek alphabet to avoid confusion with the similarities of the English word "new" and the Chinese surname Xi . The name of the variant has occasionally been mistaken as "Omnicron" among some English speakers, due to

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4662-580: The efficacy of the vaccine is 76.0% at preventing symptomatic COVID-19 beginning at 22 days following the first dose and 81.3% after the second dose. A study in Scotland found that, for symptomatic COVID-19 infection after the second dose, the vaccine is 81% effective against the Alpha variant (lineage B.1.1.7) and 61% against the Delta variant (lineage B.1.617.2). The vaccine is stable at refrigerator temperatures and has

4773-509: The fifteenth letter in the Greek alphabet . By 6 January 2022, the variant had been confirmed in 149 countries. Retrospectively, Omicron cases have been detected as occurring earlier, in October 2021. Omicron did not evolve from any other variant, but instead diverged on a distinct track, perhaps in 2020. Competing hypotheses are being examined. One origin hypothesis is that various mutations in

4884-475: The AstraZeneca vaccine provided minimal protection against mild or moderate disease infection among young people. The BBC reported on 8 February 2021 that Katherine O'Brien , director of immunisation at the WHO, felt it was "really plausible" the AstraZeneca vaccine could have a "meaningful impact" on the Beta variant (lineage B.1.351), particularly in preventing serious illness and death. The same report also indicated

4995-623: The COVID-19 vaccine produced for clinical testing was developed by Oxford University's Jenner Institute and the Oxford Vaccine Group in collaboration with Italian manufacturer Advent Srl located in Pomezia . The team is led by Sarah Gilbert , Adrian Hill , Andrew Pollard , Teresa Lambe , Sandy Douglas and Catherine Green . In February 2020, the Jenner Institute agreed a collaboration with

5106-794: The Democratic Republic of the Congo (2018–2020) . The rVSV-ZEBOV vaccine was approved for medical use in the European Union in November 2019, and in December 2019 for the United States. Zabdeno/Mvabea was approved for medical use in the European Union in July 2020. Viral vector vaccines enable antigen expression within cells and induce a robust cytotoxic T cell response, unlike subunit vaccines which only confer humoral immunity . In order to transfer

5217-690: The Deputy Chief Medical Officer for England Jonathan Van-Tam said the Witwatersrand study did not change his opinion that the AstraZeneca vaccine was "rather likely" to have an effect on severe disease from the Beta variant. The South African government subsequently cancelled the use of the AstraZeneca vaccine. In March 2021, Austria suspended the use of one batch of vaccine after two people had blood clots after vaccination, one of whom died. In total, four cases of blood clots have been identified in

5328-547: The Dominican Republic, El Salvador, India, Israel, Malaysia, Mexico, Nepal, Pakistan, the Philippines, Sri Lanka, and Taiwan regulatory authorities for emergency usage in their respective countries. South Korea granted approval of the AstraZeneca vaccine on 10 February 2021, thus becoming the first vaccine to be approved for use in that country. The regulator recommended the two-shot regimen be used in all adults, including

5439-589: The E1A and E1B viral gene region. Currently, overcoming the effects of adenovirus-specific neutralizing antibodies is being explored by vaccinologists. These studies include numerous strategies such as designing alternative Adenovirus serotypes, diversifying routes of immunization, and using prime-boost procedures. Human adenovirus serotype 5 is often used because it can be easily produced in high titers . As of April 2021, four adenovirus vector vaccines for COVID-19 have been authorized in at least one country: Zabdeno,

5550-621: The EU, the Hungarian regulator unilaterally approved the vaccine instead of waiting for EMA approval. In October 2022, the conditional marketing authorisation was converted to a standard one. On 30 January 2021, the Vietnamese Ministry of Health approved the AstraZeneca vaccine for use, becoming the first vaccine to be approved in Vietnam . The vaccine has since been approved by a number of non-EU countries, including Argentina, Bangladesh, Brazil,

5661-589: The Italian company Advent Srl for the production of a batch of 1,000 doses of a vaccine candidate for clinical trials. Originally, Oxford intended to donate the rights to manufacture and market the vaccine to any drugmaker who wanted to do so, but after the Gates Foundation urged Oxford to find a large company partner to get its COVID-19 vaccine to market, the university backed off of this offer in May 2020. The UK government then encouraged Oxford to work with AstraZeneca,

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5772-648: The Omicron variant arriving in the United States, President Joe Biden stated that the variant is "cause for concern, not panic", reiterated that the government was prepared for the variant and would have it under control and that large-scale lockdowns, similar to the ones in 2020 near the beginning of the pandemic, were "off the table for now." In December 2021, multiple Canadian provinces reinstated restrictions on gatherings and events such as sports tournaments, and tightened enforcement of proof of vaccination orders. British Columbia expressly prohibited any non-seated "organized New Year's Eve event", while Quebec announced

5883-454: The Omicron variant was detected in three samples in Nigeria that had been collected from travelers from South Africa within the last week. On the same day, public health authorities in the United States announced the country's first confirmed Omicron case. A resident of San Francisco who had been vaccinated returned from South Africa on 22 November, began showing mild symptoms on 25 November and

5994-425: The Omicron variant, comprising a 9- nucleotide sequence, may have been acquired from another coronavirus (known as HCoV-229E ), responsible for the common cold. This is not entirely unexpected —  at times, viruses within the body acquire and swap segments of genetic material from each other, and this is one common means of mutation. A link with HIV infection may explain a large number of mutations in

6105-475: The Oxford–AstraZeneca COVID-19 vaccine. The European Medicines Agency (EMA) has assessed 41 cases of anaphylaxis from around 5   million vaccinations in the United Kingdom. Capillary leak syndrome is a possible side effect of the vaccine. The European Medicines Agency (EMA) listed Guillain-Barré syndrome as a very rare side effect of the Oxford–AstraZeneca COVID-19 vaccine and added

6216-423: The Oxford–AstraZeneca vaccine was associated with a vaccine effect of 94% for COVID-19-related hospitalisation at 28–34 days post-vaccination. Combined results (all vaccinated participants, whether Pfizer–BioNTech or Oxford–AstraZeneca) showed a significant vaccine effect for prevention of COVID-19-related hospitalisation, which was comparable when restricting the analysis to those aged ≥80 years (81%). The majority of

6327-535: The US. The collaboration was also granted £68m of UK government funding, and US$ 1.2bn of US government funding, to support the development of the vaccine. In June 2020, the US National Institute of Allergy and Infectious Diseases (NIAID) confirmed that the third phase of trials for the vaccine would begin in July 2020. On 4 June, AstraZeneca announced that the COVAX program for equitable vaccine access managed by

6438-481: The WHO and financed by CEPI and GAVI had spent $ 750m to secure 300   million doses of the vaccine to be distributed to low-income or under-developed countries. Preliminary data from a study that reconstructed funding for the vaccine indicates that funding was at least 97% public, almost all from UK government departments, British and American scientific institutes, the European Commission and charities. In July 2020, AstraZeneca partnered with IQVIA to accelerate

6549-847: The WHO was alerted on 24 November, Hong Kong was the only place outside Africa that had confirmed a case of Omicron; one person who traveled from South Africa on 11 November, and another traveler who was cross-infected by this case while staying in the same quarantine hotel. On 25 November, one confirmed case was identified in Israel from a traveler returning from Malawi, along with two who returned from South Africa and one from Madagascar. All four initial cases reported from Botswana occurred among fully vaccinated individuals. On 26 November, Belgium confirmed its first case; an unvaccinated person who had travelled from Egypt via Turkey on 11 November. All three initial confirmed and suspected cases reported from Israel occurred among fully vaccinated individuals, as did

6660-410: The advantage of high transduction efficiency, transgene expression, and broad viral tropism , and can infect both dividing and non-dividing cells. A disadvantage is that many people have preexisting immunity to adenoviruses from previous exposure. The seroprevalence against Ad5 in the US population is as high as 40%–45%. Most Adenovirus vectors are replication-defective because of the deletion of

6771-556: The approach used by the Johnson & Johnson COVID-19 vaccine and the Russian Sputnik V COVID-19 vaccine . The protein of interest is the spike protein , a protein on the exterior of the virus that enables SARS-type coronaviruses to enter cells through the ACE2 receptor. Following vaccination, the production of coronavirus spike protein within the body will cause the immune system to attack

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6882-413: The clinical trials were usually mild or moderate and got better within a few days after vaccination. Vomiting, diarrhoea, fever, swelling, redness at the injection site and low levels of blood platelets occurred in less than 1 in 10 people. Enlarged lymph nodes, decreased appetite, dizziness, sleepiness, sweating, abdominal pain, itching and rash occurred in less than 1 in 100 people. An increased risk of

6993-443: The community. Japan also confirmed its first case. Two Israeli doctors tested positive and entered isolation. Both of them had received three shots of the Pfizer vaccine prior to testing positive. In Brazil, three cases of the Omicron variant were confirmed in São Paulo . Another five are under suspicion. A person in Leipzig , Germany with no travel history nor contact with travellers tested positive for Omicron. On 1 December,

7104-406: The effectiveness of a first dose of the Pfizer–BioNTech or Oxford–AstraZeneca COVID-19 vaccines against COVID-19 related hospitalisation in Scotland was based on a national prospective cohort study of 5.4   million people. Between 8 December 2020 and 15 February 2021, 1,137,775 participants were vaccinated in the study, 490,000 of whom were given the Oxford–AstraZeneca vaccine. The first dose of

7215-478: The effectiveness of public health and social measures, diagnostic methods, immune responses, antibody neutralization, or other relevant characteristics. On 26 November 2021, the WHO advised countries not to impose new restrictions on travel, instead recommending a "risk-based and scientific" approach to travel measures. On the same day, the European Centre for Disease Prevention and Control (ECDC) reported modeling indicating that strict travel restrictions would delay

7326-403: The effects of specific neutralizing antibodies limiting the use of these vaccines. These routes include intranasal , oral, intradermal , and aerosol vaccination. SARS-CoV-2 Omicron variant Omicron (B.1.1.529) is a variant of SARS-CoV-2 first reported to the World Health Organization (WHO) by the Network for Genomics Surveillance in South Africa on 24 November 2021. It

7437-429: The elderly, noting that consideration is needed when administering the vaccine to individuals over 65 years of age due to limited data from that demographic in clinical trials. On the same day, the World Health Organization (WHO) issued interim guidance and recommended the AstraZeneca vaccine for all adults, its Strategic Advisory Group of Experts also having considered use where variants were present and concluded there

7548-596: The emergence of new variants, and these nations also were struggling to gain intellectual property to develop and produce vaccines locally. At the same time, inoculation had slowed in South Africa due to vaccine hesitancy and apathy, with a nationwide vaccination rate of only 35% as of 24 November 2021. On 29 November 2021, the WHO warned countries that the variant poses a very high global risk with severe consequences and that they should prepare by accelerating vaccination of high-priority groups and strengthening health systems . WHO director-general Tedros Adhanom described

7659-464: The first North American country to report an Omicron case. On 29 November, a positive case was recorded in Darwin , Australia. The person arrived in Darwin on a repatriation flight from Johannesburg, South Africa on 25 November, and was taken to a quarantine facility, where the positive test was recorded. Two more people who travelled to Sydney from southern Africa via Singapore tested positive. Portugal reported 13 Omicron cases, all of them members of

7770-427: The first death of a person with Omicron was reported in the UK. On 16 December, New Zealand confirmed its first case of the Omicron variant, an individual who had traveled from Germany via Dubai. The first death of a person with Omicron was reported in Germany on 23 December and in Australia on 27 December. By Christmas 2021, the Omicron Strain became dominant in the US. On 3 January 2022, South Korea reported

7881-494: The first dose of the Zabdeno/Mvabea Ebola vaccine , is derived from human adenovirus serotype 26, expressing the glycoprotein of the Ebola virus Mayinga variant. Both doses are non-replicating vectors and carry the genetic code of several Ebola virus proteins. With the increasing prevalence of adenoviral vaccines, two vaccines, Ad26.COV2.S and ChadOx1-nCoV-19, have been linked to the rare clotting disorder, thrombosis with thrombocytopenia syndrome (TTS). The vaccinia virus

7992-467: The first known samples collected in Johannesburg , South Africa on 8 November 2021. The first known cases outside of South Africa were two people who travelled on 11 November: one who flew from South Africa to Hong Kong via Qatar , and another who travelled from Egypt to Belgium via Turkey . On 26 November 2021, the WHO designated B.1.1.529 as a variant of concern and named it "Omicron", after

8103-629: The first two deaths of people who tested positive post mortem for Omicron. In February 2022, Omicron accounted for 98% of publicly available genetic sequences worldwide. On 29 March 2022, Omicron subvariant BA.2 overtook BA.1 and became the dominant strain in the US. As of May 2022, BA.2.12.1 was spreading in the US and two new subvariants of Omicron named BA.4 and BA.5, first detected in January 2022, spread in South Africa. All 3 subvariants have spike protein mutations of L452 and elude immunity from prior BA1 infection. On 16 March 2023, without seeing

8214-490: The first will be offered another coronavirus vaccine for their second dose. In March 2021, the German Ministry of Health announced that the use of the vaccine in people aged 60 and below should be the result of a recipient-specific discussion, and that younger patients could still be given the AstraZeneca vaccine, but only "at the discretion of doctors, and after individual risk analysis and thorough explanation". In April,

8325-624: The flight were directed to isolate. Two travellers from South Africa who landed in Denmark tested positive for COVID-19; it was confirmed on 28 November that both carried the Omicron variant. On the same day, Austria also confirmed its first Omicron case. A detected Omicron case was reported in the Czech Republic, from a traveler who spent time in Namibia. Canada also reported its first Omicron cases, with two from travelers from Nigeria, therefore becoming

8436-474: The full‐length codon‐optimised coding sequence of SARS-CoV-2 spike protein along with a tissue plasminogen activator (tPA) leader sequence . The adenovirus is called replication-deficient because some of its essential genes required for replication were deleted and replaced by a gene coding for the spike protein. However, the HEK 293 cells used for vaccine manufacturing, express several adenoviral genes, including

8547-418: The global situation as dangerous and precarious and called for a new agreement on the handling of pandemics, as the current system disincentivizes countries from alerting others to threats that will inevitably land on their shores. CEPI CEO Richard Hatchett said that the variant fulfilled predictions that transmission of the virus in low-vaccination areas would accelerate its evolution. In preparation for

8658-482: The government to permanently suspended vaccination with AstraZeneca due to the "rare but severe incidents with low platelet counts, blood clots, and haemorrhages," since in the case of Norway, "the risk of dying after vaccination with the AstraZeneca vaccine would be higher than the risk of dying from the disease, particularly for younger people." At the same time, the Norwegian government announced their decision to wait for

8769-474: The lower price might relate to factors including investment in vaccine production infrastructure by the EU. As of March 2021 the vaccine active substance (ChAdOx1-SARS-COV-2) was being produced at several sites worldwide, with AstraZeneca claiming to have established 25 sites in 15 countries. The UK sites at that time were Oxford and Keele , with bottling and finishing in Wrexham . Other sites at that time included

8880-439: The most likely diagnosis to be of an idiopathic , short-segment, spinal cord demyelination . The other two cases of transverse myelitis, one in the vaccine group and the other in the control group, were considered to be unrelated to vaccination. A subsequent analysis, published on 19 February 2021, showed an efficacy of 76.0% at preventing symptomatic COVID-19 beginning at 22 days following the first dose, increasing to 81.3% when

8991-580: The natural VSV envelope glycoprotein is replaced with that from the Kikwit 1995 Zaire strain Ebola virus . Intramuscular injection is the commonly used route for vaccine administration. The introduction of alternate routes for immunization of viral vector vaccines can induce mucosal immunology at the site of administration, thereby limiting respiratory or gastrointestinal infections. Also, studies are being done on how these diverse routes can be used to overcome

9102-468: The new variant and make it available in three months. On 2 December, the Finlay Institute was already developing a version of Soberana Plus against the variant. Pfizer hoped to have a vaccine targeted to immunize against Omicron ready by March 2022. On 26 November 2021, the WHO asked nations to enhance surveillance and sequencing efforts, submit complete genome sequences and associated metadata to

9213-588: The newly imposed restrictions (which were set in place during their flight), after which 61 tested positive for SARS-CoV-2. A further two cases were detected in Australia. Both people landed in Sydney the previous day, and travelled from southern Africa to Sydney Airport via Doha Airport . The two people, who were fully vaccinated, entered isolation; 12 other travellers from southern Africa also entered quarantine for fourteen days, while about 260 other passengers and crew on

9324-404: The ones required for the vector to replicate. Following vaccination, the adenovirus vector enters the cells and releases its genes, in the form of DNA , which are transported to the cell nucleus ; thereafter, the cell's machinery does the transcription from DNA into mRNA and the translation into spike protein. The approach to use adenovirus as a vector to deliver spike protein is similar to

9435-580: The overall benefits of the vaccine. Following this announcement EU countries have resumed use of the vaccine with some limiting its use to elderly people at higher risk for severe COVID-19 illness. In March 2021, the Norwegian government temporarily suspended the vaccine's use, awaiting more information regarding potential adverse effects. Then, in April, the Norwegian Institute of Public Health recommended to

9546-502: The pandemic and said that travel bans went against the "norms and standards" of the World Health Organization. Some speculated that travel bans could have a significant impact on South Africa's economy by limiting tourism and could lead to other countries with economies that are reliant on tourism to hide the discovery of new variants of concern. Low vaccine coverage in less-developed nations could create opportunities for

9657-466: The participants over the age of 65 were given the Oxford–AstraZeneca vaccine. On 25 March 2021, the University of Oxford announced the start of a phase I clinical trial to investigate the efficacy of an intranasal spray method. The first country to issue a temporary or emergency approval for the Oxford–AstraZeneca vaccine was the UK. The Medicines and Healthcare products Regulatory Agency (MHRA) began

9768-447: The rare and potentially fatal thrombosis with thrombocytopenia syndrome (TTS) has been associated with mainly younger female recipients of the vaccine. Analysis of VigiBase reported embolic and thrombotic events after vaccination with Oxford–AstraZeneca, Moderna and Pfizer vaccines, found a temporally related incidence of 0.21 cases per 1 million vaccinated-days. Anaphylaxis and other allergic reactions are known side effects of

9879-620: The risk of uncontrolled HIV driving the emergence of SARS-CoV-2 variants. One hypothesis to explain the novel mutations is that SARS-CoV-2 was transmitted from humans to mice and mutated in a population of mice sometime between 2020 and 2021 before reinfecting humans. On 1 December 2022, a team of researchers from the Charité (Berlin) published a now- retracted study in Science that claimed that "data revealed genetically diverse Omicron ancestors already existed across Africa by August 2021". After

9990-548: The same batch of 1   million doses. Although no causal link with vaccination has been shown, several other countries, including Denmark, Norway, Iceland, Bulgaria, Ireland, Italy, Spain, Germany, France, the Netherlands and Slovenia also halted the vaccine rollout over the following days while waiting for the EMA to finish a safety review triggered by the cases. In April 2021, the EMA concluded its safety review and concluded that unusual blood clots with low blood platelets should be listed as very rare side effects while reaffirming

10101-439: The second dose is given 12 weeks or more after the first. However, the results did not show any protection against asymptomatic COVID-19 following only one dose. Beginning 14 days following timely administration of a second dose, with different duration from the first dose depending on trials, the results showed 66.7% efficacy at preventing symptomatic infection, and the UK arm (which evaluated asymptomatic infections in participants)

10212-480: The sequence of the Omicron variant. Indeed, in order to be affected by such a high number of mutations, the virus must have been able to evolve a long time without killing its host, which can occur in people with a weakened immune system who receive enough medical care to survive. This is the case in HIV patients in South Africa, who represent about 14% of the population (as of 2017). HIV prevention could be key to reducing

10323-560: The spike protein with antibodies and T-cells if the virus later enters the body. To manufacture the vaccine the virus is propagated on HEK 293 cell lines and then purified multiple times to completely remove the cell culture. The vaccine costs around US$ 3 to US$ 4 per dose to manufacture. On 17 December 2020, a tweet by the Belgian Budget State Secretary revealed that the European Union (EU) would pay €1.78 ( US$ 2.16 ) per dose, The New York Times suggesting

10434-487: The time the bans were announced. Other countries that also implemented travel bans include Japan, Canada, the European Union, Israel, Australia, the United Kingdom, Singapore, Malaysia, Indonesia, Morocco, and New Zealand. On 26 November 2021 the Brazilian Health Regulatory Agency recommended flight restrictions regarding the new variant. The state of New York declared a state of emergency ahead of

10545-489: The timeframe for clinical trials being planned or conducted in the US. On 31 August, AstraZeneca announced that it had begun enrolment of adults for a US-funded, 30,000-subject late-stage study. Clinical trials for the vaccine candidate were halted worldwide on 8 September, as AstraZeneca investigated a possible adverse reaction which occurred in a trial participant in the UK. Trials were resumed on 13 September after AstraZeneca and Oxford, along with UK regulators, concluded it

10656-451: The typical six-month interval for a booster dose of the vaccine to prepare for a wave of Omicron, as two doses are not enough to stop the infection. UK, South Korea and Thailand reduced to three months; Belgium, four months; France, Singapore, Taiwan, Italy and Australia, five months. Finland reduced it to three months for risk groups. Other countries continued with a six-month booster schedule. While antibody levels begin to drop at four months,

10767-481: The use of an adjuvant is unnecessary. Replicating vectors imitate natural infection, which stimulates the release of cytokines and co-stimulatory molecules that produce a strong adjuvant effect. The induction of innate immunity pathways is crucial to stimulating downstream pathways and adaptive immunity responses. Additionally, viral vectors can be produced in high quantities at relatively low costs, which enables use in low-income countries. Adenovirus vectors have

10878-513: The vaccine led to increased vaccine hesitancy across the West, even in countries that did not suspend the vaccine. In October 2022, the conditional marketing authorisation was converted to a standard one. Viral vector vaccine The first viral vector was introduced in 1972 through genetic engineering of the SV40 virus. A recombinant viral vector was first used when a hepatitis B surface antigen gene

10989-404: The vaccine's ongoing Phase III trials . The interim data reported a 70% efficacy, based on combined results of 62% and 90% from different groups of participants who were given different dosages. The decision to combine results from two different dosages was met with criticism from some who questioned why the results were being combined. AstraZeneca responded to the criticism by agreeing to carry out

11100-456: The vaccine, compared to 10 cases in the control groups. The rate of serious adverse events was balanced between the active and control groups, which suggested that the active vaccine did not pose safety concerns beyond a rate experienced in the general population. One case of transverse myelitis was reported 14 days after the second-dose was administered as being possibly related to vaccination, with an independent neurological committee considering

11211-513: The vaccinia virus was created in 1984 as a vaccine vector. Human clinical trials were conducted for viral vector vaccines against several infectious diseases including Zika virus , influenza viruses, respiratory syncytial virus , HIV , and malaria , before the vaccines that target SARS-CoV-2 , which causes COVID-19 . Two Ebola vaccines that used viral vector technology were used to combat Ebola outbreaks in West Africa (2013–2016) , and in

11322-420: The variant's impact on European countries by two weeks, possibly allowing countries to prepare for it. As with other variants, the WHO recommended that people continue to keep enclosed spaces well ventilated, avoid crowding and close contact , wear well-fitting masks, clean hands frequently, and get vaccinated. On 29 November 2021, the WHO said cases and infections were expected among those vaccinated, albeit in

11433-437: The variant's impact on the effectiveness of their vaccines. On the same day, Novavax stated that it was developing an updated vaccine requiring two doses for the Omicron variant, which the company expected to be ready for testing and manufacturing within a few weeks. On 29 November 2021, The Gamaleya Institute said that Sputnik Light should be effective against the variant, that it would begin adapting Sputnik V , and that

11544-591: The very rare side effects of the vaccine in younger individuals. The vaccine is no longer in production. AstraZeneca withdrew its marketing authorizations for the vaccine from the European market in March 2024, and worldwide by May 2024. The Oxford–AstraZeneca COVID‑19 vaccine is used to provide protection against infection by the SARS-CoV-2 virus in order to prevent COVID-19 in adults aged 18 years and older. The medicine

11655-415: The virus which they produced thanks to their qualities of immunogenicity, immunogenic stability, and safety. Specific immunogenicity properties include highly efficient gene transduction, highly specific delivery of genes to target cells, and the ability to induce potent immune responses. The immunogenicity is further enhanced through intrinsic vector motifs that stimulate the innate immunity pathways, so

11766-508: Was confirmed to have a mild case of COVID-19 on 29 November. Ireland and South Korea also reported their first cases. South Korea reported its cases from five travelers arriving in South Korea from Nigeria. On 2 December, Dutch health authorities confirmed that all 14 passengers with confirmed Omicron infection on 26 November had been previously vaccinated. The same day, the Norwegian Institute of Public Health confirmed that 50 attendees of

11877-440: Was first detected in Botswana and has spread to become the predominant variant in circulation around the world. Following the original B.1.1.529 variant, several subvariants of Omicron have emerged including: BA.1 , BA.2 , BA.3 , BA.4 , and BA.5 . Since October 2022, two subvariants of BA.5 called BQ.1 and BQ.1.1 have emerged. As of September 28, 2024, a new subvariant of Omicron labeled XEC has emerged. The new variant

11988-399: Was inconclusive as to the prevention of asymptomatic infection. Efficacy was higher at greater intervals between doses, peaking at around 80% when the second dose was given at 12 weeks or longer after the first. Preliminary results from another study with 120 participants under 55 years of age showed that delaying the second dose by up to 45 weeks increases the resulting immune response and that

12099-436: Was inserted into a vaccinia virus . Subsequently, other viruses including adenovirus , adeno-associated virus , retrovirus , cytomegalovirus , sendai virus , and lentiviruses have been designed into vaccine vectors. Vaccinia virus and adenovirus are the most commonly used viral vectors because of robust immune response it induces. The incorporation of several viruses in vaccination schemes has been investigated since

12210-561: Was no need not to recommend it. In February 2021, the government and regulatory authorities in Australia (16 February 2021) and Canada (26 February 2021) granted approval for temporary use of the vaccine. On 19 November 2021, the vaccine was approved for use in Canada. On 7 February 2021, the vaccine rollout in South Africa was suspended. Researchers from the University of the Witwatersrand released interim, non-peer-reviewed data that suggested

12321-404: Was safe to do so. AstraZeneca was later criticised for refusing to provide details about potentially serious neurological side effects in two trial participants who had received the experimental vaccine in the UK. While the trials resumed in the UK, Brazil, South Africa, Japan and India, the US did not resume clinical trials of the vaccine until 23 October. This was due to a separate investigation by

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