Measles vaccine

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 rate of vaccination within a population is greater than 92%, outbreaks of measles typically no longer occur; however, they may occur again if the rate 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. The vaccine is generally safe, even for those infected by HIV. Most children do not experience any side effects; those that do occur are usually mild, such as fever, rash, pain at the site of injection, and joint stiffness; and are short-lived. Anaphylaxis has been documented in about 3.5–10 cases per million doses. Rates of Guillain–Barré syndrome, autism and inflammatory bowel disease do not appear to be increased by measles vaccination. The vaccine is available both by itself and in combinations such as the MMR vaccine (a combination with the rubella vaccine and mumps vaccine) or the MMRV vaccine (a combination of MMR with the chickenpox vaccine). The measles vaccine is equally effective for preventing measles in all formulations, but side effects vary for different combinations. The World Health Organization (WHO) recommends measles vaccine be given at nine months of age in areas of the world where the disease is common, or at twelve months where the disease is not common. Measles vaccine is based on a live but weakened strain of measles. It comes as a dried powder which is mixed with a specific liquid before being injected either just under the skin or into a muscle. Verification that the vaccine was effective can be determined by blood tests. The measles vaccine was first introduced in 1963. In that year, the Edmonston-B strain of measles virus was turned into a vaccine by John Enders and colleagues and licensed in the United States.