Issue 1805: March 20, 2025

A: Acceptable presumptive evidence of immunity against measles includes at least one of the following:

• written documentation of adequate vaccination:
  • one or more doses of a measles-containing vaccine administered on or after the first birthday for preschool-age children and adults not at high risk
  • two doses of measles-containing vaccine for school-age children, adolescents, and adults at high risk, including college students, healthcare personnel, and international travelers
• laboratory evidence of immunity
• laboratory confirmation of measles (verbal history of measles does not count)
• birth before 1957

Although birth before 1957 is considered acceptable evidence of measles immunity, healthcare facilities should consider vaccinating unvaccinated personnel born before 1957 who do not have other evidence of immunity with 2 doses of MMR vaccine (minimum interval 28 days).

During an outbreak of measles, healthcare facilities should recommend 2 doses of MMR vaccine at the appropriate interval for unvaccinated healthcare personnel regardless of birth year if they lack laboratory evidence of measles immunity.

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A: Zero, one, or two doses of MMR vaccine are needed for the adults described below.

Zero doses:

• adults born before 1957 except healthcare personnel*
• adults born 1957 or later who are at low risk (e.g., not an international traveler or healthcare worker, or person attending college or other post-high school educational institution) and who have already received one or more documented doses of live measles vaccine
• adults with laboratory evidence of immunity or laboratory confirmation of measles

One dose of MMR vaccine:

• adults born in 1957 or later who are at low risk (e.g., not an international traveler, healthcare worker, or person attending college or other post-high school educational institution) and have no documented vaccination with live measles vaccine and no laboratory evidence of immunity or prior measles infection

Two doses of MMR vaccine:

• high-risk adults without any prior documented live measles vaccination and no laboratory evidence of immunity or prior measles infection, including:
  • healthcare personnel*
  • international travelers born in 1957 or later
  • people attending colleges and other post-high school educational institutions

People who previously received a dose of measles vaccine in 1963–1967 and are unsure which type of vaccine it was, or are sure it was inactivated measles vaccine, should be revaccinated with either one (if low-risk) or two (if high-risk) doses of MMR vaccine. If the vaccine given was the live virus vaccine, the dose is considered valid and does not need to be repeated.

* Healthcare personnel born before 1957 should be considered for MMR vaccination in the absence of an outbreak but are recommended for MMR vaccination during outbreaks.

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A: MMR can be given to children as young as 6 months of age who are at high risk of exposure such as during international travel or a community outbreak. However, doses given BEFORE 12 months of age cannot be counted toward the 2-dose series for MMR.

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A: Approximately 7% of people do not develop measles immunity after the first dose of vaccine. This occurs for a variety of reasons. The second dose is to provide another chance to develop measles immunity for people who did not respond to the first dose. About 97% of people develop immunity to measles after two doses of measles-containing vaccine.

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A: Adults with evidence of immunity, as defined in a separate question, do not need any further vaccines. No “booster” doses of MMR vaccine are recommended for either adults or children. They are considered to have life-long immunity once they have received the recommended number of MMR vaccine doses or have other acceptable evidence of immunity.

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A: Adults without evidence of immunity and no contraindications to MMR vaccine can be vaccinated without testing. Only adults without evidence of immunity might be considered for testing for measles-specific IgG antibody, but testing is not needed prior to vaccination.

CDC does not recommend measles antibody testing after MMR vaccination to verify the patient’s immune response to vaccination.

Two documented doses of MMR vaccine given on or after the first birthday and separated by at least 28 days is considered proof of measles immunity, according to ACIP. Documentation of appropriate vaccination supersedes the results of serologic testing for measles, mumps, rubella, and varicella.

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A: First of all, make sure all your patients are fully vaccinated according to the U.S. immunization schedule.

In certain circumstances, MMR is recommended for infants age 6 through 11 months. Give infants this age a dose of MMR before international travel. In addition, consider measles vaccination for infants as young as age 6 months as a control measure during a U.S. measles outbreak. Consult your state health department to find out if this is recommended in your situation. Do not count any dose of MMR vaccine as part of the 2-dose series if it is administered more than 4 days before a child’s first birthday. Instead, repeat the dose when the child is age 12 months.

In the case of a local outbreak, you also might consider vaccinating children age 12 months and older at the minimum age (12 months, instead of 12 through 15 months) and giving the second dose 4 weeks later (at the minimum interval) instead of waiting until age 4 through 6 years.

Finally, remember that infants too young for routine vaccination and people with medical conditions that contraindicate measles immunization depend on high MMR vaccination coverage among those around them. Be sure to encourage all your patients and their family members to get vaccinated if they are not immune.

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A: For routine vaccination, children without contraindications to MMR vaccine should receive 2 doses of MMR vaccine with the first dose at age 12–15 months old and the second dose at age 4–6 years old. The minimum interval is 28 days for dose 2. If you have an outbreak in your community or a child is traveling internationally, then consider using the minimum interval instead of waiting until age 4–6 years old for dose 2.

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A: Yes. Healthcare personnel (HCP) with 2 documented doses of MMR vaccine are considered to be immune regardless of the results of a subsequent serologic test for measles, mumps, or rubella. Documented age-appropriate vaccination supersedes the results of subsequent serologic testing. In contrast, HCP who do not have documentation of MMR vaccination and whose serologic test is interpreted as “indeterminate” or “equivocal” should be considered not immune and should receive 2 doses of MMR vaccine (minimum interval 28 days). ACIP does not recommend serologic testing after vaccination. For more information, see ACIP’s recommendations on the use of MMR vaccine at www.cdc.gov/mmwr/pdf/rr/rr6204.pdf, page 22.

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A: Several studies have documented the safety of measles and mumps vaccine (which are grown in chick embryo tissue culture) in children with severe egg allergy. Neither the American Academy of Pediatrics nor ACIP consider egg allergy as a contraindication to MMR vaccine. ACIP recommends routine vaccination of egg-allergic children without the use of special protocols or desensitization procedures.

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A: No. This issue has been studied extensively, including a thorough review by the independent Institute of Medicine (IOM). The IOM issued a report in 2004 that concluded there is no evidence supporting an association between MMR vaccine or thimerosal-containing vaccines and the development of autism. For more information about MMR vaccine safety, see the measles chapter of CDC’s Epidemiology and Prevention of Vaccine-Preventable Diseases (known as the “Pink Book”), at www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-13-measles.html#cdc_report_pub_study_section_10-vaccine-safety. For more information on thimerosal and vaccines in general, visit www.cdc.gov/vaccine-safety/about/thimerosal.html.

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