An Update on the Measles Outbreak in the US

What are the newest guidelines for measles vaccinations?

• Adults with no evidence of immunity should get 1 dose of MMR. Immunity is defined as documented receipt of 1 dose, or 2 doses, 4 weeks apart if high risk, of live measles virus-containing vaccine, laboratory evidence of immunity or laboratory confirmation of disease, or birthdate before 1957.
• High-risk people, including healthcare personnel, international travelers and students at post-high school educational institutions, should receive 2 doses.
• Persons who previously received a dose of MMR vaccine in 1963–1967 and are unsure which type of vaccine it was, or if it was an inactivated measles vaccine, should be revaccinated with either 1 (if low-risk) or 2 (if high-risk) doses of MMR vaccine. At the discretion of the state public health department, anyone exposed to measles in an outbreak setting can receive an additional dose of MMR vaccine even if they are considered complete for their age or risk status.

Why is a second dose of MMR necessary?

1. Women of childbearing age who have received 2 doses of rubella-containing vaccine and have rubella serum IgG levels that are not clearly positive should receive 1 additional dose of MMR vaccine (maximum of 3 doses). Further testing for serologic evidence of rubella immunity is not recommended. NOTE: MMR should not be administered to a pregnant woman.
2. Persons previously vaccinated with 2 doses of a mumps virus–containing vaccine who are identified by public health authorities as being part of a group or population at increased risk for acquiring mumps because of an outbreak should receive a third dose of a mumps virus–containing vaccine (MMR or MMRV) to improve protection. More information is available at www.cdc.gov/mmwr/volumes/67/wr/pdfs/mm6701a7-H.pdf

• The killed vaccine was found to be not effective and people who received it should be revaccinated with live vaccine.
• Persons born during or after 1957 who received killed measles vaccine or measles vaccine of unknown type, or who cannot document having been vaccinated or having laboratory-confirmed measles disease, should receive at least 1 dose of MMR.
• Some people at increased risk of exposure to measles (such as healthcare professionals and international travelers) should receive 2 doses of MMR separated by at least 4 weeks.

• People who have documentation of receiving live measles vaccine in the 1960s do not need to be revaccinated.
• People who were vaccinated prior to 1968 with either inactivated (killed) measles vaccine or measles vaccine of unknown type should be revaccinated with at least one dose of live attenuated measles vaccine. This recommendation is intended to protect people who may have received killed measles vaccine which was available in the United States in 1963 through 1967 and was not effective (see above).
• Persons vaccinated before 1979 with either killed mumps vaccine or mumps vaccine of unknown type who are at high risk for mumps infection (such as persons who work in a healthcare facility) should be considered for revaccination with 2 doses of MMR vaccine.

Please explain the Advisory Committee on Immunization Practices (ACIP)’s revised definition of evidence of immunity to measles, rubella, and mumps.

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