The MMR vaccine is very effective at protecting people against measles, mumps, and rubella, and preventing the complications caused by these diseases. People who receive MMR vaccination according to the U.S. vaccination schedule are usually considered protected for life against measles and rubella. While MMR provides effective protection against mumps for most people, immunity against mumps may decrease over time and some people may no longer be protected against mumps later in life. An additional dose may be needed if you are at risk because of a mumps outbreak. MMR is an attenuated (weakened) live virus vaccine. This means that after injection, the viruses cause a harmless infection in the vaccinated person with very few, if any, symptoms before they are eliminated from the body. Some people who get two doses of MMR vaccine may still get measles, mumps, or rubella if they are exposed to the viruses that cause these diseases. Experts are not sure why; it could be that their immune systems did not respond as well as they should have to the vaccine or their immune system’s ability to fight the infection decreased over time. However, disease symptoms are generally milder in vaccinated people.
- About 3 out of 100 people who get two doses of MMR vaccine will get measles if exposed to the virus. However, they are more likely to have a milder illness, and are also less likely to spread the disease to other people.
- Two doses of MMR vaccine are 88% (range 32% to 95%) effective at preventing mumps. Mumps outbreaks can still occur in highly vaccinated U.S. communities, particularly in settings where people have close, prolonged contact, such as universities and close-knit communities. During an outbreak, public health authorities may recommend an additional dose of MMR for people who belong to groups at increased risk for mumps. An additional dose can help improve protection against mumps disease and related complications.
- While there are not many studies available, most people who do not respond to the rubella component of the first MMR dose would be expected to respond to the second dose.
MMRV vaccine protects against four diseases: measles, mumps, rubella, and varicella (chickenpox). This vaccine is only licensed for use in children 12 months through 12 years of age. If you get MMR vaccine within 72 hours of initially being exposed to measles, you may get some protection against the disease, or have milder illness. In other cases, you may be given a medicine called immunoglobulin (IG) within six days of being exposed to measles, to provide some protection against the disease, or have mild symptoms. Unlike with measles, MMR has not been shown to be effective at preventing mumps or rubella in people already infected with the virus (i.e., post-exposure vaccination is not recommended). During outbreaks of measles or mumps, everyone without presumptive evidence of immunity should be brought up to date on their MMR vaccination. People who are already up to date on their MMR vaccination may be recommended to get an additional dose of MMR for added protection against disease.