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99-428: A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates

198-625: A respiratory burst . The main products of the neutrophil respiratory burst are strong oxidizing agents including hydrogen peroxide , free oxygen radicals and hypochlorite . Neutrophils are the most abundant type of phagocyte, normally representing 50–60% of the total circulating leukocytes, and are usually the first cells to arrive at the site of an infection. The bone marrow of a normal healthy adult produces more than 100 billion neutrophils per day, and more than 10 times that many per day during acute inflammation. Dendritic cells (DCs) are phagocytic cells present in tissues that are in contact with

297-399: A single product containing multiple drugs and/or doses. The term dosage form may also sometimes refer only to the pharmaceutical formulation of a drug product's constituent substances, without considering its final configuration as a consumable product (e.g., capsule, patch, etc.). Due to the somewhat ambiguous nature and overlap of these terms within the pharmaceutical industry, caution

396-453: A 10–11-year study of 657,461 children found that the MMR vaccine does not cause autism and actually reduced the risk of autism by seven percent. Beside the active vaccine itself, the following excipients and residual manufacturing compounds are present or may be present in vaccine preparations: Various fairly standardized abbreviations for vaccine names have developed, although the standardization

495-435: A broad immune response. Although most attenuated vaccines are viral, some are bacterial in nature. Examples include the viral diseases yellow fever , measles , mumps , and rubella , and the bacterial disease typhoid . The live Mycobacterium tuberculosis vaccine developed by Calmette and Guérin is not made of a contagious strain but contains a virulently modified strain called " BCG " used to elicit an immune response to

594-398: A cationic detergent. Many acute-phase proteins of inflammation are involved in the coagulation system. Increased levels of lactoferrin and transferrin inhibit bacterial growth by binding iron, an essential bacterial nutrient. The innate immune response to infectious and sterile injury is modulated by neural circuits that control cytokine production period. The inflammatory reflex

693-419: A central role in antiviral host defense and a cell's antiviral state. Viral components are recognized by different receptors: Toll-like receptors are located in the endosomal membrane and recognize double-stranded RNA (dsRNA), MDA5 and RIG-I receptors are located in the cytoplasm and recognize long dsRNA and phosphate-containing dsRNA respectively. When the cytoplasmic receptors MDA5 and RIG-I recognize

792-548: A complete clinical cycle of development and trials proves the vaccine is safe and has long-term effectiveness, following scientific review by a multinational or national regulatory organization, such as the European Medicines Agency (EMA) or the US Food and Drug Administration (FDA). Upon developing countries adopting WHO guidelines for vaccine development and licensure, each country has its own responsibility to issue

891-423: A condition known as "missing self". This term describes cells with abnormally low levels of a cell-surface marker called MHC I ( major histocompatibility complex ) - a situation that can arise in viral infections of host cells. They were named "natural killer" because of the initial notion that they do not require activation in order to kill cells that are "missing self". The MHC makeup on the surface of damaged cells

990-413: A given immune reaction. In some cases vaccines may result in partial immune protection (in which immunity is less than 100% effective but still reduces risk of infection) or in temporary immune protection (in which immunity wanes over time) rather than full or permanent immunity. They can still raise the reinfection threshold for the population as a whole and make a substantial impact. They can also mitigate

1089-488: A modified form of the complement response known as the prophenoloxidase (proPO) system. Antimicrobial peptides are an evolutionarily conserved component of the innate immune response found among all classes of life and represent the main form of invertebrate systemic immunity . Several species of insect produce antimicrobial peptides known as defensins and cecropins . In invertebrates, PRRs trigger proteolytic cascades that degrade proteins and control many of

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1188-461: A more rapid immune response than giving only the anthrax vaccine, which is of some benefit if exposure might be imminent. Vaccines may also contain preservatives to prevent contamination with bacteria or fungi . Until recent years, the preservative thiomersal ( a.k.a. Thimerosal in the US and Japan) was used in many vaccines that did not contain live viruses. As of 2005, the only childhood vaccine in

1287-504: A national licensure, and to manage, deploy, and monitor the vaccine throughout its use in each nation. Building trust and acceptance of a licensed vaccine among the public is a task of communication by governments and healthcare personnel to ensure a vaccination campaign proceeds smoothly, saves lives, and enables economic recovery. When a vaccine is licensed, it will initially be in limited supply due to variable manufacturing, distribution, and logistical factors, requiring an allocation plan for

1386-529: A part of a plant helps stop infection spread. Most plant immune responses involve systemic chemical signals sent throughout a plant. Plants use PRRs to recognize conserved microbial signatures. This recognition triggers an immune response. The first plant receptors of conserved microbial signatures were identified in rice ( XA21 , 1995) and in Arabidopsis ( FLS2 , 2000). Plants also carry immune receptors that recognize variable pathogen effectors. These include

1485-442: A physical barrier that is impermeable to most infectious agents, acting as the first line of defense against invading organisms. Desquamation (shedding) of skin epithelium also helps remove bacteria and other infectious agents that have adhered to the epithelial surface. Lack of blood vessels, the inability of the epidermis to retain moisture, and the presence of sebaceous glands in the dermis, produces an environment unsuitable for

1584-547: A plasma-clotting protein. On the other hand, in the horseshoe crab clotting system, components of proteolytic cascades are stored as inactive forms in granules of hemocytes, which are released when foreign molecules, like lipopolysaccharides enter. Members of every class of pathogen that infect humans also infect plants. Although the exact pathogenic species vary with the infected species, bacteria, fungi, viruses, nematodes, and insects can all cause plant disease . As with animals, plants attacked by insects or other pathogens use

1683-460: A requirement of caspase -1-like proteolytic activity of VPEγ , a cysteine protease that regulates cell disassembly during cell death. "Resistance" (R) proteins, encoded by R genes , are widely present in plants and detect pathogens. These proteins contain domains similar to the NOD Like Receptors and TLRs. Systemic acquired resistance (SAR) is a type of defensive response that renders

1782-519: A set of complex metabolic responses that lead to the formation of defensive chemical compounds that fight infection or make the plant less attractive to insects and other herbivores . (see: plant defense against herbivory ). Like invertebrates, plants neither generate antibody or T-cell responses nor possess mobile cells that detect and attack pathogens. In addition, in case of infection, parts of some plants are treated as disposable and replaceable, in ways that few animals can. Walling off or discarding

1881-438: A strong immune response. When two or more vaccines are mixed in the same formulation, the two vaccines can interfere. This most frequently occurs with live attenuated vaccines, where one of the vaccine components is more robust than the others and suppresses the growth and immune response to the other components. This phenomenon was first noted in the trivalent Sabin polio vaccine , where the amount of serotype   2 virus in

1980-402: A substantial portion of the mammalian gastrointestinal flora . Species such as B. fragilis are opportunistic pathogens , causing infections of the peritoneal cavity . They inhibit phagocytosis by affecting the phagocytes receptors used to engulf bacteria. They may also mimic host cells so the immune system does not recognize them as foreign. Staphylococcus aureus inhibits the ability of

2079-583: A virus the conformation between the caspase-recruitment domain (CARD) and the CARD-containing adaptor MAVS changes. In parallel, when TLRs in the endocytic compartments recognize a virus the activation of the adaptor protein TRIF is induced. Both pathways converge in the recruitment and activation of the IKKε/TBK-1 complex, inducing dimerization of transcription factors IRF3 and IRF7 , which are translocated in

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2178-536: Is a novel type of vaccine which is composed of the nucleic acid RNA, packaged within a vector such as lipid nanoparticles . Among the COVID-19 vaccines are a number of RNA vaccines to combat the COVID-19 pandemic and some have been approved or have received emergency use authorization in some countries. For example, the Pfizer-BioNTech vaccine and Moderna mRNA vaccine are approved for use in adults and children in

2277-398: Is a prototypical neural circuit that controls cytokine production in the spleen . Action potentials transmitted via the vagus nerve to the spleen mediate the release of acetylcholine , the neurotransmitter that inhibits cytokine release by interacting with alpha7 nicotinic acetylcholine receptors ( CHRNA7 ) expressed on cytokine-producing cells. The motor arc of the inflammatory reflex

2376-546: Is advisable when discussing them with others who may interpret the terminology differently. Dosage forms vary depending on the method/route of administration, which can include many types of liquid, solid, and semisolid forms. Common dosage forms include pills , tablets , capsules, drinks , and syrups , among others. A combination drug (or fixed-dose combination; FDC) is a product that contains more than one active ingredient (e.g., one tablet, one capsule, or one syrup with multiple drugs). In naturopathy , dosages can take

2475-616: Is altered and the NK cells become activated by recognizing this. Normal body cells are not recognized and attacked by NK cells because they express intact self MHC antigens. Those MHC antigens are recognized by killer cell immunoglobulin receptors (KIR) that slow the reaction of NK cells. The NK-92 cell line does not express KIR and is developed for tumor therapy. Like other 'unconventional' T cell subsets bearing invariant T cell receptors (TCRs), such as CD1d -restricted Natural Killer T cells , γδ T cells exhibit characteristics that place them at

2574-470: Is an important part of the healing process following tissue injury. Macrophages, from the Greek, meaning "large eaters", are large phagocytic leukocytes, which are able to move beyond the vascular system by migrating through the walls of capillary vessels and entering the areas between cells in pursuit of invading pathogens. In tissues, organ-specific macrophages are differentiated from phagocytic cells present in

2673-515: Is at the CDC's page called "Vaccine Acronyms and Abbreviations", with abbreviations used on U.S. immunization records. The United States Adopted Name system has some conventions for the word order of vaccine names, placing head nouns first and adjectives postpositively . This is why the USAN for " OPV " is "poliovirus vaccine live oral" rather than "oral poliovirus vaccine". A vaccine licensure occurs after

2772-493: Is by no means centralized or global. For example, the vaccine names used in the United States have well-established abbreviations that are also widely known and used elsewhere. An extensive list of them provided in a sortable table and freely accessible is available at a US Centers for Disease Control and Prevention web page. The page explains that "The abbreviations [in] this table (Column 3) were standardized jointly by staff of

2871-435: Is called herd immunity . Polio, which is transmitted only among humans, is targeted by an extensive eradication campaign that has seen endemic polio restricted to only parts of three countries (Afghanistan, Nigeria, and Pakistan). However, the difficulty of reaching all children, cultural misunderstandings, and disinformation have caused the anticipated eradication date to be missed several times. Vaccines also help prevent

2970-452: Is designed to immunize against a single antigen or single microorganism. A multivalent or polyvalent vaccine is designed to immunize against two or more strains of the same microorganism, or against two or more microorganisms. The valency of a multivalent vaccine may be denoted with a Greek or Latin prefix (e.g., bivalent , trivalent , or tetravalent/quadrivalent ). In certain cases, a monovalent vaccine may be preferable for rapidly developing

3069-520: Is encountered, the body recognizes the protein coat on the agent, and thus is prepared to respond, by first neutralizing the target agent before it can enter cells, and secondly by recognizing and destroying infected cells before that agent can multiply to vast numbers. Limitations to their effectiveness, nevertheless, exist. Sometimes, protection fails for vaccine-related reasons such as failures in vaccine attenuation, vaccination regimens or administration. Failure may also occur for host-related reasons if

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3168-467: Is enveloped (i.e., the particle is now inside the cell). Once inside the cell, the invading pathogen is contained inside a phagosome , which merges with a lysosome . The lysosome contains enzymes and acids that kill and digest the particle or organism. In general, phagocytes patrol the body searching for pathogens, but are also able to react to a group of highly specialized molecular signals produced by other cells, called cytokines . The phagocytic cells of

3267-522: Is more effective against bacteria, has a better shelf-life, and improves vaccine stability, potency, and safety; but, in the U.S., the European Union , and a few other affluent countries, it is no longer used as a preservative in childhood vaccines, as a precautionary measure due to its mercury content. Although controversial claims have been made that thiomersal contributes to autism , no convincing scientific evidence supports these claims. Furthermore,

3366-653: Is more expensive. Inhaled talc that has asbestos is generally accepted as being able to cause lung cancer if it is inhaled. The evidence about asbestos-free talc is less clear, according to the American Cancer Society . These are usually solutions and suspensions. Eye drops (normal saline in disposable packages) are distributed to syringe users by needle exchange programs . The injection of talc from crushed pills has been associated with pulmonary talcosis in intravenous drug users. Innate immunity The innate immune system or nonspecific immune system

3465-461: Is one of the two main immunity strategies in vertebrates (the other being the adaptive immune system ). The innate immune system is an alternate defense strategy and is the dominant immune system response found in plants , fungi , prokaryotes , and invertebrates (see Beyond vertebrates ). The major functions of the innate immune system are to: Anatomical barriers include physical, chemical and biological barriers. The epithelial surfaces form

3564-572: Is prevented. The administration of vaccines is called vaccination . Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio , measles , and tetanus from much of the world. The World Health Organization (WHO) reports that licensed vaccines are currently available for twenty-five different preventable infections . The first recorded use of inoculation to prevent smallpox occurred in

3663-537: Is rarely associated with complications in immunodeficient individuals, and rotavirus vaccines are moderately associated with intussusception . At least 19 countries have no-fault compensation programs to provide compensation for those with severe adverse effects of vaccination. The United States' program is known as the National Childhood Vaccine Injury Act , and the United Kingdom employs

3762-606: Is termed the cholinergic anti-inflammatory pathway . The parts of the innate immune system display specificity for different pathogens. Innate immune system cells prevent free growth of microorganisms within the body, but many pathogens have evolved mechanisms to evade it. One strategy is intracellular replication, as practised by Mycobacterium tuberculosis , or wearing a protective capsule, which prevents lysis by complement and by phagocytes, as in Salmonella . Bacteroides species are normally mutualistic bacteria, making up

3861-460: Is the subunit vaccine against hepatitis   B , which is composed of only the surface proteins of the virus (previously extracted from the blood serum of chronically infected patients but now produced by recombination of the viral genes into yeast ). Other examples include the Gardasil virus-like particle human papillomavirus (HPV) vaccine, the hemagglutinin and neuraminidase subunits of

3960-426: Is usually adsorbed onto alum . This presents the antigen in such a way as to produce a greater action than the simple aqueous tetanus toxoid. People who have an adverse reaction to adsorbed tetanus toxoid may be given the simple vaccine when the time comes for a booster. In the preparation for the 1990 Persian Gulf campaign, the whole cell pertussis vaccine was used as an adjuvant for anthrax vaccine. This produces

4059-507: The 2′,5′-oligoadenylate synthetase family, which degrades viral RNA. Some viruses evade this by producing molecules that interfere with IFN production. For example, the Influenza A virus produces NS1 protein, which can bind to host and viral RNA, interact with immune signaling proteins or block their activation by ubiquitination , thus inhibiting type I IFN production. Influenza A also blocks protein kinase R activation and establishment of

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4158-640: The Vaccine Damage Payment . Vaccines typically contain attenuated, inactivated or dead organisms or purified products derived from them. There are several types of vaccines in use. These represent different strategies used to try to reduce the risk of illness while retaining the ability to induce a beneficial immune response. Some vaccines contain live, attenuated microorganisms. Many of these are active viruses that have been cultivated under conditions that disable their virulent properties, or that use closely related but less dangerous organisms to produce

4257-415: The blood vessels , and attract phagocytes, especially neutrophils. Neutrophils then trigger other parts of the immune system by releasing factors that summon additional leukocytes and lymphocytes. Cytokines produced by macrophages and other cells of the innate immune system mediate the inflammatory response. These cytokines include TNF , HMGB1 , and IL-1 . The inflammatory response is characterized by

4356-840: The influenza virus, and edible algae vaccines . A subunit vaccine is being used for plague immunization. Certain bacteria have a polysaccharide outer coat that is poorly immunogenic . By linking these outer coats to proteins (e.g., toxins), the immune system can be led to recognize the polysaccharide as if it were a protein antigen. This approach is used in the Haemophilus influenzae type B vaccine . Outer membrane vesicles (OMVs) are naturally immunogenic and can be manipulated to produce potent vaccines. The best known OMV vaccines are those developed for serotype B meningococcal disease . Heterologous vaccines also known as "Jennerian vaccines", are vaccines that are pathogens of other animals that either do not cause disease or cause mild disease in

4455-448: The 16th century in China, with the earliest hints of the practice in China coming during the 10th century. It was also the first disease for which a vaccine was produced. The folk practice of inoculation against smallpox was brought from Turkey to Britain in 1721 by Lady Mary Wortley Montagu . The terms vaccine and vaccination are derived from Variolae vaccinae (smallpox of the cow),

4554-517: The CDC further explains that "Upper-case letters in these abbreviations denote full-strength doses of diphtheria (D) and tetanus (T) toxoids and pertussis (P) vaccine. Lower-case "d" and "p" denote reduced doses of diphtheria and pertussis used in the adolescent/adult-formulations. The 'a' in DTaP and Tdap stands for 'acellular', meaning that the pertussis component contains only a part of the pertussis organism." Another list of established vaccine abbreviations

4653-700: The Centers for Disease Control and Prevention, ACIP Work Groups, the editor of the Morbidity and Mortality Weekly Report (MMWR), the editor of Epidemiology and Prevention of Vaccine-Preventable Diseases (the Pink Book), ACIP members, and liaison organizations to the ACIP." Some examples are " DTaP " for diphtheria and tetanus toxoids and acellular pertussis vaccine, "DT" for diphtheria and tetanus toxoids, and "Td" for tetanus and diphtheria toxoids. At its page on tetanus vaccination,

4752-461: The NBS-LRR class of proteins. When a part of a plant becomes infected with a microbial or viral pathogen, in case of an incompatible interaction triggered by specific elicitors , the plant produces a localized hypersensitive response (HR), in which cells at the site of infection undergo rapid apoptosis to prevent spread to other parts of the plant. HR has some similarities to animal pyroptosis , such as

4851-459: The U.S. that contains thiomersal in greater than trace amounts is the influenza vaccine, which is currently recommended only for children with certain risk factors. Single-dose influenza vaccines supplied in the UK do not list thiomersal in the ingredients. Preservatives may be used at various stages of the production of vaccines, and the most sophisticated methods of measurement might detect traces of them in

4950-437: The US. A DNA vaccine uses a DNA plasmid (pDNA)) that encodes for an antigenic protein originating from the pathogen upon which the vaccine will be targeted. pDNA is inexpensive, stable, and relatively safe, making it an excellent option for vaccine delivery. This approach offers a number of potential advantages over traditional approaches, including the stimulation of both B- and T-cell responses, improved vaccine stability,

5049-467: The absence of any infectious agent and the relative ease of large-scale manufacture. Many innovative vaccines are also in development and use. While most vaccines are created using inactivated or attenuated compounds from microorganisms, synthetic vaccines are composed mainly or wholly of synthetic peptides, carbohydrates, or antigens. Vaccines may be monovalent (also called univalent ) or multivalent (also called polyvalent ). A monovalent vaccine

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5148-473: The antiviral state. The dengue virus also inhibits type I IFN production by blocking IRF-3 phosophorylation using NS2B3 protease complex. Bacteria (and perhaps other prokaryotic organisms), utilize a unique defense mechanism, called the restriction modification system to protect themselves from pathogens, such as bacteriophages . In this system, bacteria produce enzymes , called restriction endonucleases , that attack and destroy specific regions of

5247-408: The blood called monocytes . Macrophages are the most efficient phagocytes and can phagocytose substantial numbers of bacteria or other cells or microbes. The binding of bacterial molecules to receptors on the surface of a macrophage triggers it to engulf and destroy the bacteria through the generation of a " respiratory burst ", causing the release of reactive oxygen species . Pathogens also stimulate

5346-478: The body's immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the future. Vaccines can be prophylactic (to prevent or alleviate the effects of a future infection by a natural or "wild" pathogen ), or therapeutic (to fight a disease that has already occurred, such as cancer ). Some vaccines offer full sterilizing immunity , in which infection

5445-645: The border between innate and adaptive immunity. γδ T cells may be considered a component of adaptive immunity in that they rearrange TCR genes to produce junctional diversity and develop a memory phenotype . The various subsets may be considered part of the innate immune system where a restricted TCR or NK receptors may be used as a pattern recognition receptor . For example, according to this paradigm, large numbers of Vγ9/Vδ2 T cells respond within hours to common molecules produced by microbes, and highly restricted intraepithelial Vδ1 T cells will respond to stressed epithelial cells. The coagulation system overlaps with

5544-434: The cascades. In the hemolymph, which makes up the fluid in the circulatory system of arthropods , a gel-like fluid surrounds pathogen invaders, similar to the way blood does in other animals. Various proteins and mechanisms are involved in invertebrate clotting. In crustaceans, transglutaminase from blood cells and mobile plasma proteins make up the clotting system, where the transglutaminase polymerizes 210 kDa subunits of

5643-516: The clinical signs of inflammation. PRR activation and its cellular consequences have been well-characterized as methods of inflammatory cell death, which include pyroptosis , necroptosis , and PANoptosis . These cell death pathways help clear infected or aberrant cells and release cellular contents and inflammatory mediators. Chemical factors produced during inflammation ( histamine , bradykinin , serotonin , leukotrienes , and prostaglandins ) sensitize pain receptors , cause local vasodilation of

5742-722: The complement cascade can be found in many non-mammalian species including plants , birds , fish , and some species of invertebrates . White blood cells (WBCs) are also known as leukocytes . Most leukocytes differ from other cells of the body in that they are not tightly associated with a particular organ or tissue; thus, their function is similar to that of independent, single-cell organisms. Most leukocytes are able to move freely and interact with and capture cellular debris, foreign particles, and invading microorganisms (although macrophages , mast cells , and dendritic cells are less mobile). Unlike many other cells, most innate immune leukocytes cannot divide or reproduce on their own, but are

5841-498: The development of antibiotic resistance. For example, by greatly reducing the incidence of pneumonia caused by Streptococcus pneumoniae , vaccine programs have greatly reduced the prevalence of infections resistant to penicillin or other first-line antibiotics. The measles vaccine is estimated to prevent a million deaths every year. Vaccinations given to children, adolescents, or adults are generally safe. Adverse effects, if any, are generally mild. The rate of side effects depends on

5940-421: The entire plant resistant to a broad spectrum of infectious agents. SAR involves the production of chemical messengers , such as salicylic acid or jasmonic acid . Some of these travel through the plant and signal other cells to produce defensive compounds to protect uninfected parts, e.g., leaves. Salicylic acid itself, although indispensable for expression of SAR, is not the translocated signal responsible for

6039-418: The environment. Histamine dilates blood vessels , causing the characteristic signs of inflammation, and recruits neutrophils and macrophages. The word 'phagocyte' literally means 'eating cell'. These are immune cells that engulf, or ' phagocytose ', pathogens or particles. To engulf a particle or pathogen, a phagocyte extends portions of its plasma membrane , wrapping the membrane around the particle until it

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6138-424: The eradication of smallpox , one of the most contagious and deadly diseases in humans. Other diseases such as rubella, polio , measles, mumps, chickenpox , and typhoid are nowhere near as common as they were a hundred years ago thanks to widespread vaccination programs. As long as the vast majority of people are vaccinated, it is much more difficult for an outbreak of disease to occur, let alone spread. This effect

6237-408: The external environment, mainly the skin (where they are often called Langerhans cells ), and the inner mucosal lining of the nose , lungs , stomach , and intestines . They are named for their resemblance to neuronal dendrites , but dendritic cells are not connected to the nervous system . Dendritic cells are very important in the process of antigen presentation , and serve as a link between

6336-563: The eyes and mouth. Inflammation is one of the first responses of the immune system to infection or irritation. Inflammation is stimulated by chemical factors released by injured cells. It establishes a physical barrier against the spread of infection and promotes healing of any damaged tissue following pathogen clearance. The process of acute inflammation is initiated by cells already present in all tissues, mainly resident macrophages , dendritic cells , histiocytes , Kupffer cells , and mast cells . These cells present receptors contained on

6435-414: The finished product, as they may in the environment and population as a whole. Many vaccines need preservatives to prevent serious adverse effects such as Staphylococcus infection, which in one 1928 incident killed 12 of 21 children inoculated with a diphtheria vaccine that lacked a preservative. Several preservatives are available, including thiomersal, phenoxyethanol , and formaldehyde . Thiomersal

6534-544: The first vertebrates. Nevertheless, invertebrates possess mechanisms that appear to be precursors of these aspects of vertebrate immunity. Pattern recognition receptors (PRRs) are proteins used by nearly all organisms to identify molecules associated with microbial pathogens. TLRs are a major class of pattern recognition receptor, that exists in all coelomates (animals with a body-cavity), including humans. The complement system exists in most life forms. Some invertebrates, including various insects, crabs , and worms utilize

6633-447: The following symptoms: The complement system is a biochemical cascade of the immune system that helps, or "complements", the ability of antibodies to clear pathogens or mark them for destruction by other cells. The cascade is composed of many plasma proteins, synthesized in the liver , primarily by hepatocytes . The proteins work together to: The three different complement systems are classical, alternative and lectin. Elements of

6732-518: The form of decoctions and herbal teas , in addition to the more conventional methods mentioned above. The route of administration (ROA) for drug delivery depends on the dosage form of the substance . Different dosage forms may be available for a particular drug, especially if certain conditions restrict the ROA. For example, if a patient is unconscious or experiencing persistent nausea and vomiting , oral administration may not be feasible, necessitating

6831-539: The general population, a high standard of safety is required. As part of a multinational licensing of a vaccine, the World Health Organization Expert Committee on Biological Standardization developed guidelines of international standards for manufacturing and quality control of vaccines, a process intended as a platform for national regulatory agencies to apply for their own licensing process. Vaccine manufacturers do not receive licensing until

6930-433: The host can still become infected. Once antibodies are produced, they may promote immunity in any of several ways, depending on the class of antibodies involved. Their success in clearing or inactivating a pathogen will depend on the amount of antibodies produced and on the extent to which those antibodies are effective at countering the strain of the pathogen involved, since different strains may be differently susceptible to

7029-413: The host's immune system does not respond adequately or at all. Host-related lack of response occurs in an estimated 2-10% of individuals, due to factors including genetics, immune status, age, health and nutritional status. One type of primary immunodeficiency disorder resulting in genetic failure is X-linked agammaglobulinemia , in which the absence of an enzyme essential for B cell development prevents

7128-407: The host's immune system from generating antibodies to a pathogen . Host–pathogen interactions and responses to infection are dynamic processes involving multiple pathways in the immune system. A host does not develop antibodies instantaneously: while the body's innate immunity may be activated in as little as twelve hours, adaptive immunity can take 1–2 weeks to fully develop. During that time,

7227-437: The immune system include macrophages, neutrophils , and dendritic cells. Phagocytosis of the hosts' own cells is common as part of regular tissue development and maintenance. When host cells die, either by apoptosis or by cell injury due to an infection, phagocytic cells are responsible for their removal from the affected site. By helping to remove dead cells preceding growth and development of new healthy cells, phagocytosis

7326-444: The immune system. Some products of the coagulation system can contribute to non-specific defenses via their ability to increase vascular permeability and act as chemotactic agents for phagocytic cells . In addition, some of the products of the coagulation system are directly antimicrobial . For example, beta-lysine , a protein produced by platelets during coagulation , can cause lysis of many Gram-positive bacteria by acting as

7425-427: The immunodominant antigen of the pathogen or a surface protein that enables the formation of neutralizing antibodies. The subgroup of genetic vaccines encompass viral vector vaccines, RNA vaccines and DNA vaccines. Viral vector vaccines use a safe virus to insert pathogen genes in the body to produce specific antigens , such as surface proteins , to stimulate an immune response . An mRNA vaccine (or RNA vaccine )

7524-813: The innate and adaptive immune systems . Basophils and eosinophils are cells related to the neutrophil. When activated by a pathogen encounter, histamine -releasing basophils are important in the defense against parasites and play a role in allergic reactions , such as asthma . Upon activation, eosinophils secrete a range of highly toxic proteins and free radicals that are highly effective in killing parasites, but may also damage tissue during an allergic reaction. Activation and release of toxins by eosinophils are, therefore, tightly regulated to prevent any inappropriate tissue destruction. Natural killer cells (NK cells) do not directly attack invading microbes. Rather, NK cells destroy compromised host cells, such as tumor cells or virus-infected cells, recognizing such cells by

7623-514: The limited supply and which population segments should be prioritized to first receive the vaccine. Dosage form The term unit dose can also refer to non-reusable packaging, particularly when each drug product is individually packaged. However, the FDA differentiates this by referring to it as unit-dose "packaging" or "dispensing" . Depending on the context, multi(ple) unit dose may refer to multiple distinct drug products packaged together or

7722-480: The macrophage to produce chemokines, which summon other cells to the site of infection. Neutrophils, along with eosinophils and basophils , are known as granulocytes due to the presence of granules in their cytoplasm, or as polymorphonuclear cells (PMNs) due to their distinctive lobed nuclei . Neutrophil granules contain a variety of toxic substances that kill or inhibit growth of bacteria and fungi. Similar to macrophages, neutrophils attack pathogens by activating

7821-429: The mechanisms of the innate immune system of invertebrates—including hemolymph coagulation and melanization . Proteolytic cascades are important components of the invertebrate immune system because they are turned on more rapidly than other innate immune reactions because they do not rely on gene changes. Proteolytic cascades function in both vertebrate and invertebrates, even though different proteins are used throughout

7920-445: The microorganism. Examples of toxoid-based vaccines include tetanus and diphtheria . Not all toxoids are for microorganisms; for example, Crotalus atrox toxoid is used to vaccinate dogs against rattlesnake bites. Rather than introducing an inactivated or attenuated microorganism to an immune system (which would constitute a "whole-agent" vaccine), a subunit vaccine uses a fragment of it to create an immune response. One example

8019-402: The new protective inoculations then being developed. The science of vaccine development and production is termed vaccinology . There is overwhelming scientific consensus that vaccines are a very safe and effective way to fight and eradicate infectious diseases. The immune system recognizes vaccine agents as foreign, destroys them, and "remembers" them. When the virulent version of an agent

8118-483: The nucleus, where they induce IFN production with the presence of a particular transcription factor and activate transcription factor 2. IFN is secreted through secretory vesicles , where it can activate receptors on both the cell it was released from ( autocrine ) or nearby cells (paracrine). This induces hundreds of interferon-stimulated genes to be expressed. This leads to antiviral protein production, such as protein kinase R , which inhibits viral protein synthesis, or

8217-438: The number of cases dropped to fewer than 150 per year (median of 56). In early 2008, there were 64 suspected cases of measles. Fifty-four of those infections were associated with importation from another country, although only thirteen percent were actually acquired outside the United States; 63 of the 64 individuals either had never been vaccinated against measles or were uncertain whether they had been vaccinated. Vaccines led to

8316-414: The oral and intravenous doses of a drug like paracetamol differ for the same reason. Talc is an excipient often used in pharmaceutical tablets that may end up being crushed to a powder against medical advice or for recreational use. Also, illicit drugs that occur as white powder in their pure form are often cut with cheap talc . Natural talc is cheap but contains asbestos while asbestos-free talc

8415-399: The organism being treated. The classic example is Jenner's use of cowpox to protect against smallpox. A current example is the use of BCG vaccine made from Mycobacterium bovis to protect against tuberculosis . Genetic vaccines are based on the principle of uptake of a nucleic acid into cells, whereupon a protein is produced according to the nucleic acid template. This protein is usually

8514-493: The phagocyte to respond to chemokine signals. M. tuberculosis , Streptococcus pyogenes , and Bacillus anthracis utilize mechanisms that directly kill the phagocyte. Bacteria and fungi may form complex biofilms , protecting them from immune cells and proteins; biofilms are present in the chronic Pseudomonas aeruginosa and Burkholderia cenocepacia infections characteristic of cystic fibrosis . Type I interferons (IFN), secreted mainly by dendritic cells , play

8613-815: The products of multipotent hematopoietic stem cells present in bone marrow . The innate leukocytes include: natural killer cells , mast cells, eosinophils , basophils ; and the phagocytic cells include macrophages , neutrophils , and dendritic cells, and function within the immune system by identifying and eliminating pathogens that might cause infection. Mast cells are a type of innate immune cell that resides in connective tissue and in mucous membranes. They are intimately associated with wound healing and defense against pathogens, but are also often associated with allergy and anaphylaxis . When activated, mast cells rapidly release characteristic granules, rich in histamine and heparin , along with various hormonal mediators and chemokines , or chemotactic cytokines into

8712-434: The severity of infection and response to a vaccine. Elderly (above age 60), allergen-hypersensitive , and obese people have susceptibility to compromised immunogenicity , which prevents or inhibits vaccine effectiveness, possibly requiring separate vaccine technologies for these specific populations or repetitive booster vaccinations to limit virus transmission . Severe side effects are extremely rare. Varicella vaccine

8811-453: The severity of infection, resulting in a lower mortality rate , lower morbidity , faster recovery from illness, and a wide range of other effects. Those who are older often display less of a response than those who are younger, a pattern known as Immunosenescence . Adjuvants commonly are used to boost immune response, particularly for older people whose immune response to a simple vaccine may have weakened. The efficacy or performance of

8910-495: The successful conclusion of the development cycle and further the clinical trials and other programs involved through Phases   I–III demonstrating safety, immunoactivity, immunogenetic safety at a given specific dose, proven effectiveness in preventing infection for target populations, and enduring preventive effect (time endurance or need for revaccination must be estimated). Because preventive vaccines are predominantly evaluated in healthy population cohorts and distributed among

9009-482: The surface or within the cell, named pattern recognition receptors (PRRs), which recognize molecules that are broadly shared by pathogens but distinguishable from host molecules, collectively referred to as pathogen-associated molecular patterns (PAMPs). At the onset of an infection, burn, or other injuries, these cells undergo activation (one of their PRRs recognizes a PAMP) and release inflammatory mediators , like cytokines and chemokines, which are responsible for

9108-453: The survival of microbes . In the gastrointestinal and respiratory tract , movement due to peristalsis or cilia, respectively, helps remove infectious agents. Also, mucus traps infectious agents. Gut flora can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or cell surface attachment sites. The flushing action of tears and saliva helps prevent infection of

9207-509: The term devised by Edward Jenner (who both developed the concept of vaccines and created the first vaccine) to denote cowpox . He used the phrase in 1798 for the long title of his Inquiry into the Variolae vaccinae Known as the Cow Pox , in which he described the protective effect of cowpox against smallpox. In 1881, to honor Jenner, Louis Pasteur proposed that the terms should be extended to cover

9306-475: The use of alternative routes, such as inhalational , buccal , sublingual , nasal , suppository , or parenteral . A specific dosage form may also be required due to issues such as chemical stability or pharmacokinetic properties. For instance, insulin cannot be given orally because it is extensively metabolized in the gastrointestinal tract (GIT) before it reaches the bloodstream , preventing it from reaching therapeutic target destinations. Similarly,

9405-483: The vaccine had to be reduced to stop it from interfering with the "take" of the serotype   1 and   3 viruses in the vaccine. It was also noted in a 2001 study to be a problem with dengue vaccines, where the DEN-3 serotype was found to predominate and suppress the response to DEN-1, -2 and -4 serotypes. Vaccines typically contain one or more adjuvants , used to boost the immune response. Tetanus toxoid, for instance,

9504-570: The vaccine in question. Some common side effects include fever, pain around the injection site, and muscle aches. Additionally, some individuals may be allergic to ingredients in the vaccine. MMR vaccine is rarely associated with febrile seizures . Host-("vaccinee")-related determinants that render a person susceptible to infection, such as genetics , health status (underlying disease, nutrition, pregnancy, sensitivities or allergies ), immune competence , age, and economic impact or cultural environment can be primary or secondary factors affecting

9603-409: The vaccine is dependent on several factors: If a vaccinated individual does develop the disease vaccinated against ( breakthrough infection ), the disease is likely to be less virulent than in unvaccinated cases. Important considerations in an effective vaccination program: In 1958, there were 763,094 cases of measles in the United States; 552 deaths resulted. After the introduction of new vaccines,

9702-769: The vaccine. The live attenuated vaccine containing strain Yersinia pestis EV is used for plague immunization. Attenuated vaccines have some advantages and disadvantages. Attenuated, or live, weakened, vaccines typically provoke more durable immunological responses. But they may not be safe for use in immunocompromised individuals, and on rare occasions mutate to a virulent form and cause disease. Some vaccines contain microorganisms that have been killed or inactivated by physical or chemical means. Examples include IPV ( polio vaccine ), hepatitis A vaccine , rabies vaccine and most influenza vaccines . Toxoid vaccines are made from inactivated toxic compounds that cause illness rather than

9801-417: The viral DNA of invading bacteriophages. Methylation of the host's own DNA marks it as "self" and prevents it from being attacked by endonucleases. Restriction endonucleases and the restriction modification system exist exclusively in prokaryotes. Invertebrates do not possess lymphocytes or an antibody-based humoral immune system, and it is likely that a multicomponent, adaptive immune system arose with

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