Measles vaccine

Measles vaccine is a vaccine that is very effective at preventing measles. After one dose 85% of children nine months of age and 95% over twelve months of age are immune. 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 93% 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 the disease if given within a couple of days of being exposed.