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Bacillus Calmette–Guérin (BCG) vaccine is a vaccine primarily used against tuberculosis (TB). It is named after its inventors Albert Calmette and Camille Guérin. In countries where TB or leprosy is common, one dose is recommended in healthy babies as soon after birth as possible. In areas where TB is not common, only children at high risk are typically immunized, while suspected cases of TB are individually tested for and treated. Adults who do not have TB and have not been previously immunized but are frequently exposed may be immunized as well. BCG also has some effectiveness against Buruli ulcer infection and other nontuberculous mycobacteria infections. Additionally it is sometimes used as part of the treatment of bladder cancer.
Vaccination is the administration of a vaccine to help the immune system develop protection from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body's adaptive immunity, they help prevent sickness from an infectious disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results. Herd immunity protects those who may be immunocompromised and cannot get a vaccine because even a weakened version would harm them. The effectiveness of vaccination has been widely studied and verified. 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 elimination of diseases such as polio and tetanus from much of the world. However, some diseases, such as measles outbreaks in America, have seen rising cases due to relatively low vaccination rates in the 2010s — attributed, in part, to vaccine hesitancy.
A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. 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 to further recognize and destroy any of the microorganisms associated with that agent that it may encounter in the future. Vaccines can be prophylactic, or therapeutic.
Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than 40 °C (104 °F), cough, runny nose, and inflamed eyes. Small white spots known as Koplik's spots may form inside the mouth two or three days after the start of symptoms. A red, flat rash which usually starts on the face and then spreads to the rest of the body typically begins three to five days after the start of symptoms. Common complications include diarrhea, middle ear infection (7%), and pneumonia (6%). These occur in part due to measles-induced immunosuppression. Less commonly seizures, blindness, or inflammation of the brain may occur. Other names include morbilli, rubeola, red measles, and English measles. Both rubella, also known as German measles, and roseola are different diseases caused by unrelated viruses.
The MMR vaccine is a vaccine against measles, mumps, and rubella. The first dose is generally given to children around 9 months to 15 months of age, with a second dose at 15 months to 6 years of age, with at least 4 weeks between the doses. After two doses, 97% of people are protected against measles, 88% against mumps, and at least 97% against rubella. The vaccine is also recommended for those who do not have evidence of immunity, those with well-controlled HIV/AIDS, and within 72 hours of exposure to measles among those who are incompletely immunized. It is given by injection.
Herd immunity is a form of indirect protection from infectious disease that can occur with some diseases when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity. Immune individuals are unlikely to contribute to disease transmission, disrupting chains of infection, which stops or slows the spread of disease. The greater the proportion of immune individuals in a community, the smaller the probability that non-immune individuals will come into contact with an infectious individual.
In biology, immunity is the capability of multicellular organisms to resist harmful microorganisms. Immunity involves both specific and nonspecific components. The nonspecific components act as barriers or eliminators of a wide range of pathogens irrespective of their antigenic make-up. Other components of the immune system adapt themselves to each new disease encountered and can generate pathogen-specific immunity.
Intramuscular injection, often abbreviated IM, is the injection of a substance into a muscle. In medicine, it is one of several methods for parenteral administration of medications. Intramuscular injection may be preferred because muscles have larger and more numerous blood vessels than subcutaneous tissue, leading to faster absorption than subcutaneous or intradermal injections. Medication administered via intramuscular injection is not subject to the first-pass metabolism effect which affects oral medications.
Vaccine hesitancy refers to a delay in acceptance, or refusal of vaccines despite the availability of vaccine services. Vaccine hesitancy is complex and context specific, varying across time, place and vaccines. It is influenced by factors such as complacency, convenience and confidence. The term covers outright refusals to vaccinate, delaying vaccines, accepting vaccines but remaining uncertain about their use, or using certain vaccines but not others. Among the hesitant are groups known as "anti-vaxxers" or "anti vax", who are generally against vaccination.
A vaccine adverse event (VAE), sometimes referred to as a vaccine injury, is an adverse event caused by vaccination. The World Health Organization (WHO) knows VAEs as Adverse Events Following Immunization (AEFI).
Statens Serum Institut, is a Danish sector research institute located on the island of Amager in Copenhagen. Its purpose is to combat and prevent infectious diseases, congenital disorders, and threats from weapons of mass destruction.
The Bandim Health Project works with population based health research in one of the world's poorest countries, Guinea-Bissau in West Africa.
An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by "killing" the virus.
Claims of a link between the MMR vaccine and autism have been extensively investigated and found to be false. The link was first suggested in the early 1990s and came to public notice largely as a result of the 1998 Lancet MMR autism fraud, characterised as "perhaps the most damaging medical hoax of the last 100 years". The fraudulent research paper authored by Andrew Wakefield and published in The Lancet claimed to link the vaccine to colitis and autism spectrum disorders. The paper was retracted in 2010 but is still cited by anti-vaccinationists.
Vaccination policy is the health policy a government adopts in relation to vaccination. Vaccination policies have been developed over the approximately two centuries since the invention of vaccination with the purpose of eradicating disease from, or creating a herd immunity for, the population the government aims to protect. Vaccination advisory committees within each country are usually responsible for providing information to governments that is used to make evidence-based decisions regarding vaccine and immunization policy.
Measles vaccine protects against becoming infected with measles. Nearly all of those who do not develop immunity after a single dose develop it after a second dose. When rates of vaccination within a population are greater than 92%, outbreaks of measles typically no longer occur; however, they may occur again if rates of vaccination decrease. The vaccine's effectiveness lasts many years. It is unclear if it becomes less effective over time. The vaccine may also protect against measles if given within a couple of days after exposure to measles.
Preben Christian Alexander von Magnus was a Danish virologist who is known for his research on influenza, polio vaccination and monkeypox. He gave his name to the Von Magnus phenomenon.
Non-specific effects of vaccines are effects which go beyond the specific protective effects against the targeted diseases. Non-specific effects can be strongly beneficial by increasing protection against non-targeted infections. This has been shown with two live attenuated vaccines, BCG vaccine and measles vaccine, through multiple randomized controlled trials. Theoretically, non-specific effects of vaccines may be detrimental, increasing overall mortality despite providing protection against the target diseases. Although observational studies suggest that diphtheria-tetanus-pertussis vaccine (DTP) may be detrimental, these studies are at high risk of bias and have failed to replicate when conducted by independent groups.
Trained immunity is the modification of cells in the innate immune system to create a "memory" of a pathogen. Trained immunity creates no antibodies in preparation for a second encounter. Instead, the immunity is mediated mostly by epigenetic modifications, alterations in gene expression and cellular function without changes to the original DNA sequence. The resulting immunity lasts up to several months, in contrast to the classical immunological memory, and is usually unspecific because there is no production of specific antibodies/receptors.
Misinformation related to vaccination and immunization circulates in mass media and social media. Intentional spreading of false information and conspiracy theories have also been propagated by the general public and celebrities. Misinformation related to vaccination fuels vaccine hesitancy and thereby results in disease outbreaks. Although opposition to vaccination has existed for centuries, the internet and social media has recently facilitated the spread of vaccine-related misinformation. Unsubstantiated safety concerns related to vaccines are often presented as scientific information on the internet.
References
- ↑ Winkel, Klaus (2011). Danskere i tropisk Afrika : fra slavehandler til bistandsarbejder (1. udgave. ed.). Århus: Klim. ISBN 8779559271.
- ↑ "Background". Bandim Health Project. SSI. Retrieved 28 September 2015.
- ↑ Prentice, AM; Savy, M; Darboe, MK; Moore, SE (April 2009). "Commentary: Challenging public health orthodoxies--prophesy or heresy?". International Journal of Epidemiology. 38 (2): 591–3. doi:10.1093/ije/dyn363. PMC 2663722 . PMID 19174540.
- ↑ Benn, CS; Netea, MG; Selin, LK; Aaby, P (September 2013). "A small jab - a big effect: nonspecific immunomodulation by vaccines". Trends in Immunology. 34 (9): 431–9. doi:10.1016/j.it.2013.04.004. PMID 23680130.
- ↑ Shann, F (February 2013). "Nonspecific effects of vaccines and the reduction of mortality in children". Clinical Therapeutics. 35 (2): 109–14. doi:10.1016/j.clinthera.2013.01.007. PMID 23375475.
- ↑ "Meeting of Global Advisory Committee on Vaccine Safety, 18-19 June 2008". Wkly Epidemiol Rec. 83 (32): 287–92. Aug 2008. PMID 18689006.
