The MMR vaccine (measles, mumps, and rubella) is generally safe, but like all vaccines, it can cause side effects. Most side effects are mild and temporary, occurring in the first few days after vaccination[1].
- Common mild side effects include soreness, pain, redness, or swelling at the injection site, fever, and a mild rash. Some people may also experience temporary joint pain or stiffness, especially in adolescent or adult women[1][2][5].
- Other mild reactions can include drowsiness, tiredness, a head cold, runny nose, cough, or swelling of the salivary glands[5].
- In rare cases, children may have a febrile seizure (a seizure caused by fever) after the MMR vaccine, typically within 7–14 days. The risk is about 1 in 3,000 to 4,000 children[1][4].
- Adults may experience arthralgia (joint pain) or a temporary form of arthritis. This is more common in women who were not immune to rubella before vaccination and is usually mild and short-lived[1][6].
- The MMRV (measles, mumps, rubella, and varicella) vaccine can also cause a mild chickenpox-like rash several days after vaccination[5].
Rare but serious side effects can occur, but are much less common than the risks from natural infection with measles, mumps, or rubella:
- Immune thrombocytopenic purpura (ITP): A rare blood disorder causing a temporary decrease in platelets and increased risk of bleeding may occur after MMR vaccination, with an estimated risk of about 1 in 40,000 vaccinated children[1].
- Allergic reactions such as anaphylaxis are extremely rare[2][6].
- Encephalitis (brain swelling) and other neurologic complications are exceedingly rare. Only a handful of cases have been documented in individuals with severely weakened immune systems[1].
Serious adverse events like seizures, meningitis, or Guillain-Barré syndrome have been reported but are very rare—less than 6 incidents per 100,000 doses in older children and adults, with no significant increase in risk compared to the background rate[6].
The benefits of the MMR vaccine vastly outweigh the small risk of side effects, especially compared to the serious complications associated with measles, mumps, and rubella infections, which can include pneumonia, long-term brain damage, and death[2][4].
References
- [1] Measles, Mumps, Rubella (MMR) Vaccine Safety – CDC
- [2] Fact Checked: The Measles Vaccine is Safe and Effective – American Academy of Pediatrics
- [4] Measles, Mumps and Rubella – Vaccine Safety and Effectiveness
- [5] Measles, mumps, rubella, varicella (chickenpox) – Better Health Channel
- [6] Safety of measles, mumps, and rubella vaccine in adolescents and adults – PMC
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