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 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.
Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Most infections are asymptomatic or have a mild clinical course, but in some outbreaks, the mortality rate approaches 10%. Signs and symptoms may vary from mild to severe, and usually start two to five days after exposure. Symptoms often develop gradually, beginning with a sore throat and fever. In severe cases, a grey or white patch develops in the throat, which can block the airway, and create a barking cough similar to what is observed in croup. The neck may also swell, in part due to the enlargement of the facial lymph nodes. Diphtheria can also involve the skin, eyes, or genitals, and can cause complications, including myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low levels of platelets.
In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization.
An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, similar to endotoxins, may be released during lysis of the cell. Gram negative pathogens may secrete outer membrane vesicles containing lipopolysaccharide endotoxin and some virulence proteins in the bounding membrane along with some other toxins as intra-vesicular contents, thus adding a previously unforeseen dimension to the well-known eukaryote process of membrane vesicle trafficking, which is quite active at the host–pathogen interface.
The DPT vaccine or DTP vaccine is a class of combination vaccines against three infectious diseases in humans: diphtheria, pertussis, and tetanus (lockjaw). The vaccine components include diphtheria and tetanus toxoids, and either killed whole cells of the bacterium that causes pertussis or pertussis antigens. The term toxoid refers to vaccines which use an inactivated toxin produced by the pathogen which they are targeted against to generate an immune response. In this way, the toxoid vaccine generates an immune response which is targeted against the toxin which is produced by the pathogen and causes disease, rather than a vaccine which is targeted against the pathogen itself. The whole cells or antigens will be depicted as either "DTwP" or "DTaP", where the lower-case "w" indicates whole-cell inactivated pertussis and the lower-case "a" stands for "acellular". In comparison to alternative vaccine types, such as live attenuated vaccines, the DTP vaccine does not contain any live pathogen, but rather uses inactivated toxoid to generate an immune response; therefore, there is not a risk of use in populations that are immune compromised since there is not any known risk of causing the disease itself. As a result, the DTP vaccine is considered a safe vaccine to use in anyone and it generates a much more targeted immune response specific for the pathogen of interest.
A toxoid is an inactivated toxin whose toxicity has been suppressed either by chemical (formalin) or heat treatment, while other properties, typically immunogenicity, are maintained. Toxins are secreted by bacteria, whereas toxoids are altered form of toxins; toxoids are not secreted by bacteria. Thus, when used during vaccination, an immune response is mounted and immunological memory is formed against the molecular markers of the toxoid without resulting in toxin-induced illness. Such a preparation is also known as an anatoxin. There are toxoids for prevention of diphtheria, tetanus and botulism.
A vaccination schedule is a series of vaccinations, including the timing of all doses, which may be either recommended or compulsory, depending on the country of residence. A vaccine is an antigenic preparation used to produce active immunity to a disease, in order to prevent or reduce the effects of infection by any natural or "wild" pathogen. Vaccines go through multiple phases of trials to ensure safety and effectiveness.
A vaccine adverse event (VAE), sometimes referred to as a vaccine injury, is an adverse event believed to have been caused by vaccination. The World Health Organization (WHO) knows VAEs as Adverse Events Following Immunization (AEFI).
In immunology, the Arthus reaction is a type of local type III hypersensitivity reaction. Type III hypersensitivity reactions are immune complex-mediated, and involve the deposition of antigen/antibody complexes mainly in the vascular walls, serosa, and glomeruli. This reaction is usually encountered in experimental settings following the injection of antigens.
A booster dose is an extra administration of a vaccine after an earlier (primer) dose. After initial immunization, a booster provides a re-exposure to the immunizing antigen. It is intended to increase immunity against that antigen back to protective levels after memory against that antigen has declined through time. For example, tetanus shot boosters are often recommended every 10 years, by which point memory cells specific against tetanus lose their function or undergo apoptosis.
In immunology, passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy. Passive immunization is used when there is a high risk of infection and insufficient time for the body to develop its own immune response, or to reduce the symptoms of ongoing or immunosuppressive diseases. Passive immunization can be provided when people cannot synthesize antibodies, and when they have been exposed to a disease that they do not have immunity against.
Hepatitis B vaccine is a vaccine that prevents hepatitis B. The first dose is recommended within 24 hours of birth with either two or three more doses given after that. This includes those with poor immune function such as from HIV/AIDS and those born premature. It is also recommended that health-care workers be vaccinated. In healthy people, routine immunization results in more than 95% of people being protected.
The Haemophilus influenzae type B vaccine, also known as Hib vaccine, is a vaccine used to prevent Haemophilus influenzae type b (Hib) infection. In countries that include it as a routine vaccine, rates of severe Hib infections have decreased more than 90%. It has therefore resulted in a decrease in the rate of meningitis, pneumonia, and epiglottitis.
Pertussis vaccine is a vaccine that protects against whooping cough (pertussis). There are two main types: whole-cell vaccines and acellular vaccines. The whole-cell vaccine is about 78% effective while the acellular vaccine is 71–85% effective. The effectiveness of the vaccines appears to decrease by between 2 and 10% per year after vaccination with a more rapid decrease with the acellular vaccines. The vaccine is only available in combination with tetanus and diphtheria vaccines. Pertussis vaccine is estimated to have saved over 500,000 lives in 2002.
Meningococcal vaccine refers to any vaccine used to prevent infection by Neisseria meningitidis. Different versions are effective against some or all of the following types of meningococcus: A, B, C, W-135, and Y. The vaccines are between 85 and 100% effective for at least two years. They result in a decrease in meningitis and sepsis among populations where they are widely used. They are given either by injection into a muscle or just under the skin.
Cocooning, also known as the Cocoon Strategy, is a vaccination strategy to protect infants and other vulnerable individuals from infectious diseases by vaccinating those in close contact with them. If the people most likely to transmit an infection are immune, their immunity creates a "cocoon" of protection around the newborn.
A Vaccine Information Statement (VIS) is a document designed by the Centers for Disease Control and Prevention (CDC) to provide information to a patient receiving a vaccine in the United States. The National Childhood Vaccine Injury Act requires that medical professionals provide a VIS to patients before receiving certain vaccinations. The VIS includes information about the vaccine's benefits and risks, a description of the vaccine, indications and contraindications, instructions for patients experiencing an adverse reaction, and additional resources.
Tetanus vaccine, also known as tetanus toxoid (TT), is a toxoid vaccine used to prevent tetanus. During childhood, five doses are recommended, with a sixth given during adolescence.
DTaP-IPV-HepB vaccine is a combination vaccine whose generic name is diphtheria and tetanus toxoids and acellular pertussis adsorbed, hepatitis B (recombinant) and inactivated polio vaccine or DTaP-IPV-Hep B. It protects against the infectious diseases diphtheria, tetanus, pertussis, poliomyelitis, and hepatitis B.
A hexavalent vaccine, or 6-in-1 vaccine, is a combination vaccine with six individual vaccines conjugated into one, intended to protect people from multiple diseases. The term usually refers to the children's vaccine that protects against diphtheria, tetanus, pertussis, poliomyelitis, haemophilus B, and hepatitis B, which is used in more than 90 countries around the world including in Europe, Canada, Australia, Jordan, and New Zealand.
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