The standard measles vaccine schedule

Children in the United States receive the measles vaccine in two doses: the first at 12 to 15 months old, and the second between 4 and 6 years old, before school entry. Both doses are part of the MMR vaccine, which protects against measles, mumps, and rubella in a single shot.

This two-dose schedule gives children strong protection. After the first dose, about 93 percent of children develop immunity to measles. The second dose raises that to 97 percent or higher. The spacing between doses matters—they must be at least 28 days apart, and the second dose works best when given after the first has had time to work.

Infants younger than 12 months are not routinely vaccinated because maternal antibodies (immunity passed from mother during pregnancy) can interfere with the vaccine's effectiveness. However, infants in high-risk situations—such as those traveling internationally or during an outbreak—may receive an early dose at 6 to 11 months, followed by the standard two-dose series later.

Key Takeaways

  • The first MMR dose is given at 12 to 15 months old, and the second between 4 and 6 years old.
  • Two doses provide 97 percent protection against measles; one dose alone leaves a small gap in immunity.
  • Infants under 12 months are not routinely vaccinated because maternal antibodies interfere with vaccine effectiveness.
  • Children who miss the standard schedule can catch up at any age, and the vaccine is recommended through age 18 for anyone without documented immunity.

What happens if a child misses the standard schedule

Children who miss doses on the standard timeline can still receive the vaccine later. The CDC recommends that anyone born in 1957 or later who has not been vaccinated or does not have documented immunity should receive two doses, spaced at least 28 days apart, at any age.

If a child is behind on the vaccine schedule, the two doses do not need to restart from the beginning. A child who received one dose at age 2 can receive the second dose at age 7, and both will count toward full protection. The key requirement is the 28-day spacing between them.

Catch-up vaccination is especially important before travel, before school entry, or if measles is circulating in the community. A healthcare provider can review a child's vaccination record and recommend the fastest safe path to full protection.

Measles vaccine timing during outbreaks

During a measles outbreak, timing becomes more urgent. Children as young as 6 months old may receive an early dose if they are in an affected area or will be traveling to one. This early dose does not count as one of the two required doses—children still need the standard two-dose series starting at 12 months.

If a child receives an early dose at 6 to 11 months, the first official dose of the two-dose series should be given at 12 to 15 months (at least 28 days after the early dose). The second dose follows the normal schedule, 28 days or more after the first official dose.

Outbreak situations are rare in the United States, but they do occur when vaccination rates drop in a community. A healthcare provider or local health department can advise whether an early dose makes sense for a specific child.

Special circumstances that change the vaccine schedule

Certain medical conditions or medications can delay the measles vaccine. Children with severe allergies to vaccine ingredients (particularly gelatin or neomycin) should not receive MMR. Children with weakened immune systems due to HIV, certain cancers, or immunosuppressive medications may not be able to receive the live vaccine and need to discuss alternatives with their doctor.

Pregnancy is a reason to delay the vaccine—MMR should not be given during pregnancy, though it is safe to give immediately after delivery. Women of childbearing age without immunity should be vaccinated before becoming pregnant.

Recent blood transfusions or certain blood products can interfere with vaccine effectiveness. A healthcare provider can determine how long to wait after a transfusion before vaccinating and whether revaccination is needed later.

Why the two-dose schedule exists

The two-dose schedule protects against the small percentage of children who do not respond to the first dose. About 3 to 5 percent of vaccinated children do not develop immunity from a single dose—reasons include individual immune system differences, timing of maternal antibodies, or the vaccine batch itself. The second dose catches these children and brings overall protection to 97 percent or higher.

This high level of population immunity matters because measles spreads easily. One infected person can infect 12 to 18 others in an unvaccinated group. When 95 percent or more of a community is vaccinated, measles cannot spread efficiently, even protecting the small number of people who cannot be vaccinated for medical reasons.

Documenting vaccination and school requirements

Schools and childcare centers require proof of measles vaccination before enrollment. This proof usually comes from a vaccination record card, a healthcare provider's documentation, or a state immunization registry. The specific requirement varies by state—some require two doses before kindergarten entry, while others accept one dose at school entry and require the second by a certain grade.

Parents should keep vaccination records in a safe place and request copies from their healthcare provider if records are lost. Many states allow parents to check their child's vaccination record online through the state health department's immunization registry.

Medical or religious exemptions exist in most states, but the rules differ significantly. A healthcare provider can explain what documentation is needed in your state if an exemption is being considered.

Frequently Asked Questions

Can a child get the measles vaccine before 12 months?

Routine vaccination starts at 12 to 15 months because younger infants still have maternal antibodies that interfere with the vaccine. However, infants 6 to 11 months old can receive an early dose if they are traveling internationally or during an outbreak. This early dose does not replace the standard two-dose series.

What if my child is allergic to eggs?

The MMR vaccine does not contain eggs, so egg allergy is not a reason to avoid it. Children with severe allergies to gelatin or neomycin should discuss MMR with their healthcare provider, as these are actual vaccine ingredients. Most children with food allergies can safely receive MMR.

Do adults need the measles vaccine?

Adults born in 1957 or later without documented vaccination or immunity should receive two doses, spaced 28 days apart. Adults born before 1957 are generally considered immune due to natural infection. Healthcare workers, travelers, and people in outbreak areas should verify their immunity status with a healthcare provider.

Can my child get measles even after vaccination?

Breakthrough infection is rare but possible. After two doses, about 3 in 100 vaccinated people may still contract measles if exposed. Vaccinated people who do get measles typically have milder illness with lower risk of serious complications than unvaccinated people.

How do I know if my child needs a second dose?

Check your child's vaccination record for two separate MMR doses, at least 28 days apart, given on or after the first birthday. If the record shows only one dose or you are unsure, contact your healthcare provider. They can review the record and recommend whether a second dose is needed.