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The measles-mumps-rubella (MMR) vaccine is a live-attenuated combined vaccine used to prevent infectious diseases (measles, mumps, and rubella). It is also indicated in specific patient populations as post-exposure prophylaxis to measles, mumps, and/or rubella. Measles, mumps and rubella diseases remain widespread in all parts of the world but are most common in Asia, Africa and South America. Outbreaks occur in Europe, North America and Australia/New Zealand where populations are unvaccinated or under-vaccinated.
Measles, mumps, and rubella are viral diseases that are primarily spread from person to person through coughing and sneezing. The measles virus can stay in the air for up to two hours after an infected person has sneezed or coughed and can be spread to others even with the infected person is no longer in the area. Mumps can also be spread from close contact activities and from coming into contact with an infected individual’s saliva. If an individual has rubella during pregnancy is can be passed to the developing baby.
Measles is caused by the measles virus and spreads through the air by droplet or direct contact with nasal or throat secretions of infected persons, and less commonly, by articles soiled with nasal and throat secretions. Affected persons will present initially with tiredness, fever, cough, runny nose, red eyes and white spots inside the mouth. This is followed by a red blotchy skin rash 3-7 days later. The rash usually spreads from the face down to the rest of the body. In severe cases, lungs, guts and brain can get involved and lead to serious consequences or even death.
Mumps is caused by the mumps virus which affects the salivary glands and sometimes the nerve tissue. It is spread by droplet and direct contact with the saliva of an infected person. The disease is characterized by painful swelling of the salivary glands, usually at the cheek(s). Sometimes, there may be complications like deafness, or infection of the brain, pancreas, testicles or ovaries.
Rubella, also known as “German Measles”, is caused by rubella virus. It can be transmitted by contact with secretions from nose and throat of infected persons through droplet spread or direct contact with patients. Children usually present with fever, headache, malaise, diffuse rash, enlargement of lymph nodes, upper respiratory symptoms and conjunctivitis. Some patients may not have rash at all. Complications include arthritis, thrombocytopenia and encephalitis.
Rubella infection can cause anomalies in the developing foetus. Congenital rubella syndrome (CRS) is likely to occur in infants born to women who got infected during the first 3 months of pregnancy. CRS is characterised by deafness, cataract, heart malformations and mental retardation.
The combination MMR vaccine can confer life-long protection against measles, mumps, and rubella. This vaccine was introduced into the developed world in the late 1960s and immediately cut the incidence of measles, mumps, and rubella in these countries by about 98%. The current MMR vaccine is administered parenterally and is made up of live, attenuated versions of the measles, mumps, and rubella viruses. The vaccine is effective in inducing protective anti-measles antibody production in 98% of children vaccinated at age 15 months. Similar levels of protection are achieved for mumps and rubella. Both antibody and cell-mediated immune responses are mounted and long-lasting memory is induced.
It should be noted that maternal antibodies have a significant influence on the effectiveness of the MMR vaccine. Mothers who experienced a natural measles infection in their childhood pass on anti-measles antibodies that last for 11 months after birth in their infants. While these maternal antibodies protect the infant, they also bind to the vaccine before it can induce the infant's immune system to produce its own antibodies to the virus. The MMR vaccine was thus originally administered to infants at 15 months of age, to ensure that all maternal antibodies had disappeared. However, for unknown reasons, mothers who are immune to measles because of vaccination produce anti-measles antibodies that last only 9 months in their offspring. Under the original regimen, these infants were without antibody protection against measles for close to 6 months. Administration of the MMR vaccine is now recommended at 12–15 months, depending on maternal history. Despite these measures, local measles outbreaks occurred in the United States in the 1980s in children who had been vaccinated according to the recommended regimen. It was found that anti-measles antibody production is not initiated or is sub-optimal in 2–5% of 12-month-old infants receiving one dose of MMR vaccine. Current regimens recommend that a first dose of MMR vaccine be given at age 12–15 months followed by a second dose at age 4–5 years.
MMR is a live vaccine preparation containing attenuated strains of all three viruses and was first introduced in the US in 1972. The types of viruses used in the production of MMR vaccines vary according to different manufacturers. Nearly all the combination MMR vaccines contain the RA 27/3 rubella strain, but differ in the measles and mumps strains. MMR II contains the Moraten measles strain and the Merck JL mumps strain. Trimovax, Priorix, and Trivac contain the Schwarz measles strain, but differ with respect to the mumps virus components. Trimovax contains the Urabe Am9 mumps virus vaccine strain, whereas Priorix and Trivivac contain the RIT-4385 and Sevapharma JL-based strains, respectively. Tresivac contains the Edmonston–Zagreb measles and Leningrad-Zagreb mumps virus strains. This ability to combine the three single antigen vaccines into one combined vaccine has many advantages, not least being that only one injection is required.
MMR vaccine has been shown to be highly immunogenic, with high seroconversion rates (between 95 and 100%) being achieved for each of the three component vaccines. For the measles component, the degree of immunogenicity depends on the age of the infant to be immunized, since maternally-derived measles antibodies may interfere with the development of immunity to measles if the vaccine is given early in the first year of life. This factor is important in determining the age at which to immunize. In terms of vaccine efficacy, studies have shown that the combined vaccine is as effective in producing immunity as each of the separate vaccines and that the immunity induced by immunization with MMR is long-lasting and may even be lifelong.
References
Measles Virus
Mumps Virus
Rubella Virus
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