Most people need two doses of the MMR vaccine for full protection against measles, mumps, and rubella. Children receive the first dose between 12 and 15 months of age and the second dose between ages 4 and 6. Adults who missed one or both doses can still catch up.
The Standard Two-Dose Schedule
The CDC recommends two doses for all children. The first dose goes in at 12 to 15 months old, and the second at 4 to 6 years old. The minimum gap between doses is 28 days, so if a child falls behind schedule, the two doses don’t need to be spaced years apart.
That second dose matters more than many people realize. A single dose of MMR is 93% effective against measles, 72% effective against mumps, and 97% effective against rubella. Adding the second dose bumps measles protection to 97% and mumps protection to 86%. Mumps remains the hardest of the three diseases to fully prevent with vaccination, which is one reason outbreaks still pop up on college campuses even among vaccinated populations.
How Many Doses Adults Need
If you were born in 1957 or later and don’t have written proof of vaccination, you need at least one dose. Whether you need one or two depends on your situation.
Most adults need just one dose to be considered adequately vaccinated. However, two doses are recommended if you’re a healthcare worker, a college or university student, or planning international travel. In these higher-risk settings, the extra protection from a second dose is worth it. If you’re getting two doses as an adult, they should be spaced at least 28 days apart.
If you were born before 1957, you’re generally considered immune without any vaccination. The measles vaccine wasn’t introduced until 1963, so nearly everyone born before 1957 caught measles during childhood and developed natural immunity. This applies regardless of what country you were born in. The one exception: healthcare workers born before 1957 may still be asked to show proof of immunity or get vaccinated, depending on their state and employer.
Proof of Immunity Without Vaccination
You don’t necessarily need the shots if you can demonstrate immunity another way. Acceptable evidence includes written documentation of prior vaccination, a blood test showing protective antibodies, lab-confirmed history of measles, or birth before 1957. A blood test (sometimes called a titer) is the most common alternative for adults who were vaccinated as children but lost their records. If the test shows adequate antibodies, you won’t need additional doses.
International Travel
Travel changes the math. If you’re heading to an area with active measles transmission, the CDC recommends being fully vaccinated at least two weeks before departure. If your trip is less than two weeks away and you’re not protected, getting a dose before you leave still provides some benefit.
For infants traveling internationally, the timeline shifts earlier than the standard schedule. Babies between 6 and 11 months old can receive an early dose before travel, but that dose doesn’t count toward their routine series. They’ll still need a dose at 12 to 15 months and another at 4 to 6 years, bringing their total to three shots. Children over 12 months who haven’t started the series should get their first dose right away and the second dose 28 days later. The same accelerated schedule applies to teens and adults without evidence of immunity.
Requirements for School and Work
Colleges and universities typically require two documented doses of MMR for enrollment. Healthcare facilities have similar requirements, though the specifics vary by state. Some states require two doses of measles vaccine for healthcare workers, while others accept one dose plus a blood test confirming immunity. If you’re starting a new healthcare job or enrolling in college, check the requirements early so you have time to space out doses if needed.
Pregnancy and Timing
The MMR vaccine uses live, weakened viruses, so it’s not given during pregnancy. If you need a dose and are planning to become pregnant, the recommendation is to wait at least one month after vaccination before conceiving. If you’re unsure of your immunity status, a blood test before or early in pregnancy can clarify whether you’ll need a dose afterward.