Important Facts About the Measles Vaccines

Measles (rubeola) is a highly infectious viral disease that can lead to serious health problems, especially in children under 5 years of age.[1] Prior to 1963, when the first measles vaccine was developed, almost all children had measles before the age of 15.[2] In 2000, measles was declared eliminated in the United States due to high rates of vaccination at the time.

For many years the Centers for Disease Control and Prevention (CDC) has advised that the best way to protect against measles is to receive two doses of the measles, mumps and rubella (MMR) vaccine,[3] which the Food and Drug Administration (FDA) approved in 1978. Children may be vaccinated with the measles, mumps, rubella and varicella (MMRV) vaccine, also called PROQUAD, instead, which adds protection against chickenpox (varicella). The FDA approved this vaccine in 2005.

Both MMR and MMRV vaccines are injected in the upper arm or outer thigh; they contain live attenuated versions of the measles virus.[4],[5] Most people who receive either of these vaccines are protected from measles for life.

The long-standing CDC recommendation has been that children should routinely receive their first dose of a measles-containing vaccine at 12 to 15 months of age and the second dose at 4 to 6 years of age. Infants aged 6 to 11 months should receive an additional dose before international travel, if applicable.

Older children and adults without immunity to measles should receive at least one dose of the MMR vaccine. Booster injections are not routinely recommended for individuals who are fully vaccinated against measles.

Given that the two-dose measles vaccine schedule was not implemented in the United States until 1989, a second vaccine dose may be recommended for certain high-risk individuals who were vaccinated before that time.[6]

The recent rise of the anti-vaccine movement and vaccine hesitancy are threatening our protection against measles, leading to local outbreaks of measles in many areas of the country. In 2025, there were 2,286 confirmed measles cases, including 242 related hospitalizations and three deaths in the United States; as of early April 2026, there have already been 1,671 confirmed measles cases across several states.[7] Undoubtedly, many other cases have not been reported. Experts warn that if measles outbreaks persist for more than 12 months, the United States will lose its measles-elimination status.

Dangers of measles

Measles is spread through the air when an infected person coughs, sneezes or even breathes. A single infected person can infect up to 18 nearby people without immunity against the virus.[8]

Measles causes fever, cough, inflammation in the nasal mucous membranes (resulting in runny nose) and conjunctivitis (eye inflammation resulting in red, watery eyes), typically followed by a rash that starts on the face and spreads to the head, trunk and extremities.

It can lead to diarrhea, ear infection and pneumonia. Even after recovery, children who have had measles are at high risk of late complications, including malnutrition and blindness.

Measles also can cause temporary loss of immunity, making infected people more likely to catch other infectious diseases. This effect can last up to a year in measles survivors.

Notably, measles-related encephalitis (inflammation of the brain) is a rare but serious complication that can arise during the first week of infection, within one to six months after infection, or even several years after recovery.

Effectiveness and safety of measles vaccines

A Cochrane review of clinical studies conducted through 2019 assessed the effectiveness of the MMR and MMRV vaccines in healthy children aged up to 15 years. It showed that two doses of these vaccines were 96% effective in preventing measles, and one dose was 95% effective in preventing the disease.[9]

The review found a small association between measles vaccines and febrile seizures (high fever that can cause convulsions); the highest estimated risk of this vaccine-induced adverse effect was one case per 1,150 administered doses. However, febrile seizures occur normally at least once in up to 4% of healthy children under the age of 5 years. Therefore, the review concluded that the current evidence supports the use of both vaccines for mass immunization against measles. Notably, the CDC advises that the risk of fever and febrile seizures is higher with the first dose of the MMRV vaccine than after separate MMR and varicella vaccines in younger children.[10]

Although a small percentage of vaccinated individuals may still be infected with measles if they are exposed to the viruses, they are less likely to spread the infection to others and they usually have milder symptoms than unvaccinated individuals.[11]

Due to the high transmissibility of the measles virus and the seriousness of measles infection, a high coverage level (more than 95%) of both recommended doses of a measles vaccine is necessary at the population level to maintain adequate herd immunity against measles and prevent community transmission. Herd immunity means that when unvaccinated individuals are surrounded by vaccinated people, they are protected from the infectious disease. It protects vulnerable community members who cannot be vaccinated, such as those who are pregnant and individuals with weakened immune systems (including those with solid organ transplants or those undergoing treatment for cancer).

A recent study estimated that a 10% decrease in MMR vaccination in the United States may result in 11.1 million measles cases over 25 years, as opposed to just 5,800 total cases with a 5% increase in vaccination.[12]

No association with autism

Autism is a developmental disorder that is usually diagnosed in preschool children. Although a 1998 study published in The Lancet claimed that the MMR vaccine was associated with autism, this study has been retracted due to data fabrications and other issues.[13]

Numerous large, well-designed retrospective studies found no association between measles vaccines and autism. For example, a 2019 Danish study of over 650,000 children strongly concluded that the MMR vaccine neither increases the risk of autism nor triggers autism in susceptible children with certain risk factors; it also does not increase clustering of autism cases during any specific time periods after vaccination.[14] Similarly, an analysis of studies involving over 1.2 million children from four developed countries found no relationship between MMR vaccination and autism or autism spectrum disorder.[15]

What You Can Do

You should get vaccinated for measles if you have never had the disease nor received two doses of a measles vaccine and are not immunocompromised or pregnant.

If you provide care for any healthy individuals who are over the age of 12 months, you should also get them vaccinated. Like with any vaccine, measles vaccines can cause an allergic reaction or other adverse effects, such as fever, pain or rash at the injection site. However, it is safer to receive a measles vaccine than to risk contracting measles.

Although supervised use of vitamin A may be recommended in patients who are infected with measles, particularly in those who are deficient in the vitamin, it is not useful for preventing measles. Instead, excessive intake of this vitamin can cause toxicity; symptoms include blurry vision, dizziness, nausea and vomiting.
 

References

[1] Centers for Disease Control and Prevention. About measles. May 29, 2024. https://www.cdc.gov/measles/about/index.html. Accessed March 10, 2026.

[2] Centers for Disease Control and Prevention. History of measles. May 9, 2024. https://www.cdc.gov/measles/about/history.html. Accessed March 10, 2026.

[3] Centers for Disease Control and Prevention. Measles vaccination. January 17, 2025. https://www.cdc.gov/measles/vaccines/index.html. Accessed March 10, 2026.

[4] Merck Sharp & Dohme LLC. Label: Measles, mumps, and rubella virus vaccine live (MMR II). November 2025. https://www.fda.gov/media/75191/download. Accessed March 10, 2026.

[5] Merck Sharp & Dohme LLC. Label: Label: Measles, mumps, rubella and varicella virus vaccine (MMRV, ProQuad). November 2024. https://www.fda.gov/media/147563/download. Accessed March 10, 2026.

[6] Do LAH, Mulholland K. Measles 2025. N Engl J Med. 2025;393(24):2447-2458.

[7] Centers for Disease Control and Prevention. Measles cases and outbreaks. March 6, 2026. https://www.cdc.gov/measles/data-research/index.html. Accessed March 10, 2026.

[8] Do LAH, Mulholland K. Measles 2025. N Engl J Med. 2025;393(24):2447-2458.

[9] Pietrantonj C Di, Rivetti A, Marchione P, et al. Vaccines for measles, mumps, rubella, and varicella in children (review). Cochrane Database Syst Rev. 2021;1(11):CD004407.

[10] Centers for Disease Control and Prevention. MMRV vaccine (measles, mumps, rubella, and varicella): What you need to know. January 31, 2025. https://www.cdc.gov/vaccines/hcp/current-vis/downloads/mmrv.pdf. Accessed March 10, 2026.

[11] Centers for Disease Control and Prevention. Measles vaccination. January 17, 2025. https://www.cdc.gov/measles/vaccines/index.html. Accessed March 10, 2026.

[12] Kiang M V, Bubar KM, Maldonado Y, et al. Modeling reemergence of vaccine-eliminated infectious diseases under declining vaccination in the US. JAMA. 2025;333(24):2176-2187.

[13] The Editors of The Lancet. Retraction—Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 2010;375(9713):445.

[14] Hviid A, Hansen JV, Frisch M, Melbye M. Measles, mumps, rubella vaccination and autism: A nationwide cohort study. Ann Intern Med. 2019;170(8):513-520.

[15] Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies. Vaccine. 2014;32(29):3623-3629.