The MMR vaccine is given in two doses during childhood. The first dose is recommended between 12 and 15 months of age, and the second dose between 4 and 6 years old. This schedule applies to children in the United States and has remained consistent in recent years, with no changes to the recommended ages for 2025.
The Standard Two-Dose Schedule
The first dose at 12 to 15 months is timed to coincide with when maternal antibodies (protection passed from mother to baby during pregnancy) begin to fade. Before that point, those inherited antibodies can actually interfere with the vaccine’s ability to trigger a strong immune response. Most pediatricians give the first dose at the 12-month well-child visit.
The second dose, given between ages 4 and 6, isn’t a booster in the traditional sense. It’s a catch-up shot designed to protect the small percentage of children who didn’t develop full immunity after the first dose. About 93% of children are protected against measles after one dose. After two doses, that rises to 97%. For mumps, effectiveness jumps from 72% to 86% with the second dose. A single dose provides 97% protection against rubella.
The second dose is typically given before kindergarten entry, which is why many states require it for school enrollment.
Early Vaccination for International Travel
Infants traveling internationally can receive the MMR vaccine as early as 6 months of age. Measles circulates widely in many parts of the world, and this early dose provides some short-term protection for young travelers. However, a dose given before 12 months of age does not count toward the routine two-dose series. Children vaccinated early still need two additional doses starting on or after their first birthday, spaced at least 28 days apart.
For children 12 months and older who are traveling, both doses can be given before departure as long as they’re separated by at least 28 days. This means a toddler could receive the second dose well before age 4 if travel plans require it.
The MMRV Combination Option
A combination vaccine called MMRV adds chickenpox (varicella) protection to the standard MMR. It’s approved for children ages 1 through 12 and reduces the total number of shots at a visit. One thing to be aware of: children who receive MMRV for their first dose (at 12 to 15 months) have a slightly higher chance of developing a fever and febrile seizure in the 7 to 10 days afterward compared to children who get MMR and the chickenpox vaccine as separate shots. This increased risk applies only to the first dose. By the second dose at ages 4 through 6, there is no added seizure risk with the combination vaccine.
What to Expect After the Shot
Side effects from the MMR vaccine tend to show up later than with most other childhood vaccines. Rather than soreness or fussiness in the first day or two, MMR reactions typically appear 5 to 12 days after the shot. The most common is a fever, which can occasionally reach above 103°F. Some children develop a faint, measles-like rash about 7 to 12 days after vaccination. Both are signs of the immune system responding to the vaccine and resolve on their own. They are not contagious.
Adults and Catch-Up Vaccination
The MMR vaccine isn’t just for kids. Adults born in 1957 or later who can’t show written proof of vaccination, a blood test confirming immunity, or a history of having the diseases need at least one dose. Verbal reports of past vaccination don’t count as evidence of immunity.
One dose is sufficient for most adults. However, certain groups need two doses:
- College students entering or attending a postsecondary institution
- Healthcare workers with direct patient contact
- International travelers going to areas where measles is common
- Close contacts of immunocompromised people who can’t be vaccinated themselves
People born before 1957 are generally considered immune because measles, mumps, and rubella circulated so widely during their childhood that nearly everyone was exposed. The exception is healthcare workers born before 1957, who may still be asked to show lab-confirmed immunity or get vaccinated.
There is no blanket recommendation for adults to get a second dose as a catch-up measure. If you received one dose as a child and don’t fall into a higher-risk group, that single dose is considered adequate.
During a Measles Outbreak
When measles cases appear in a community, vaccination timelines can shift. Infants as young as 6 months may be offered an early dose, and children who have received only their first dose may be given the second dose ahead of schedule rather than waiting until age 4. The minimum interval between doses is 28 days, so a child who got the first shot at 12 months could receive the second at 13 months during an active outbreak. Adults in the affected area who lack evidence of immunity are also urged to get vaccinated promptly.