MMR vaccine

MMR vaccine is a vital immunization against three significant viral diseases. It contains live, attenuated strains of the Measles virus, Mumps virus, and Rubella virus. The World Health Organization includes it on its List of Essential Medicines, and its widespread use has dramatically reduced the global incidence of these infections.

Composition and formulation

The vaccine is a lyophilized preparation containing live, attenuated viral strains. The measles component is typically derived from the Edmonston-Enders strain, first isolated by John F. Enders and propagated in chick embryo cell culture. The mumps component often originates from the Jeryl Lynn strain, named for the daughter of Maurice Hilleman who isolated it at the Merck & Co. laboratories. The rubella component commonly uses the RA 27/3 strain, developed by Stanley Plotkin at the Wistar Institute using human diploid lung fibroblasts. These components are combined with stabilizers like sorbitol and gelatin, and reconstituted with a sterile diluent, usually containing water for injection. The final formulation is administered via subcutaneous injection.

Efficacy and duration of protection

Clinical trials and post-licensure surveillance demonstrate high efficacy. Following two recommended doses, protection against measles is approximately 97%, while efficacy against mumps is about 88% and against rubella exceeds 95%. The Centers for Disease Control and Prevention notes that immunity appears to be very long-lasting, likely lifelong for most individuals. Outbreaks, such as those documented at Disneyland in 2015 or within certain Orthodox Jewish communities in New York City, typically occur among unvaccinated or under-vaccinated populations, underscoring the vaccine's effectiveness in preventing community spread when coverage is high.

Safety and side effects

The vaccine has a well-established safety profile monitored by organizations like the Food and Drug Administration and the Global Advisory Committee on Vaccine Safety. Common, mild adverse reactions can include fever, a transient rash, or swelling of the parotid glands. More serious events, such as febrile seizures or temporary thrombocytopenia, are rare. Extensive research by bodies like the Institute of Medicine and the Cochrane Collaboration has found no credible evidence linking it to autism, a claim originating from a now-retracted 1998 paper in The Lancet by Andrew Wakefield.

History and development

Individual vaccines for measles, mumps, and rubella were first licensed in the United States during the 1960s. The combined trivalent vaccine was developed by Maurice Hilleman and his team at Merck & Co. and licensed in 1971, building on earlier work by John F. Enders on measles attenuation. The rubella component was later improved with the introduction of the more immunogenic RA 27/3 strain, which replaced earlier strains like the Cendehill strain or the HPV-77 strain. This improved formulation became standard in many countries, including those following recommendations from the National Health Service in the United Kingdom.

Public health impact and controversies

The vaccine's impact on global health has been profound. The World Health Organization and UNICEF spearhead efforts through the Expanded Programme on Immunization and the Measles & Rubella Initiative, aiming for regional elimination. The Americas were declared free of endemic measles in 2016. However, coverage has been hampered by misinformation, notably the debunked autism link promoted by Andrew Wakefield, leading to declines in uptake in areas like Wales and certain California communities. These declines have resulted in resurgent outbreaks, investigated by agencies like Public Health England.

Administration and schedule

The standard schedule, as recommended by the Advisory Committee on Immunization Practices and the World Health Organization, involves two doses. The first dose is typically given at 12-15 months of age, and the second dose before school entry, between 4-6 years. In regions with high disease burden, the World Health Organization may recommend an earlier first dose at 9 months. It is often administered concurrently with other immunizations, such as the varicella vaccine (as MMRV vaccine), during visits to pediatricians following schedules like those from the American Academy of Pediatrics. Special catch-up schedules are advised for older children, adolescents, and adults lacking evidence of immunity, particularly for groups like college students or healthcare workers. Category:Vaccines Category:World Health Organization essential medicines