How do I assess and ensure measles‑mumps‑rubella (MMR) immunity in an adult with unknown vaccination status, including serologic testing, vaccination schedule, contraindications (pregnancy, severe immunodeficiency), and post‑exposure prophylaxis?

Assessing and Ensuring MMR Immunity in Adults with Unknown Vaccination Status

All adults born in 1957 or later without documented immunity should receive at least one dose of MMR vaccine, with specific high-risk groups requiring a two-dose series spaced at least 28 days apart. 1

Determining Immunity Status

Adults are presumed immune to measles, mumps, and rubella if they meet any of the following criteria:

• Born before 1957 (except healthcare personnel, who require documentation regardless of birth year) 2, 1
• Laboratory evidence of immunity (serum IgG antibodies) for all three diseases 2
• Laboratory confirmation of disease for measles, mumps, or rubella 3
• Documentation of age-appropriate vaccination with MMR vaccine 1

Important caveat: Physician-diagnosed disease is not acceptable evidence of immunity for rubella and was removed as acceptable evidence for measles and mumps in 2012 ACIP revisions. 2, 3 Clinical diagnosis of rubella is unreliable, and only serologic testing (IgG antibodies) provides reliable evidence of immunity. 2

Serologic Testing Approach

When to test versus vaccinate directly:

• Healthcare personnel born before 1957: Consider serologic testing or proceed directly to two-dose vaccination series if no laboratory evidence of immunity exists 1
• Women of childbearing age: Test for rubella immunity specifically; if negative, vaccinate immediately (unless pregnant) 1
• General adults with unknown status: Vaccination without serologic testing is acceptable and often more cost-effective than testing 2

Acceptable serologic assays include: EIA (most common), latex agglutination, immunofluorescence assay, passive hemagglutination, hemolysis-in-gel, and virus neutralization tests. 2 Any antibody level above the standard positive cutoff is considered evidence of immunity. 2

Vaccination Schedule by Risk Category

One-Dose Recipients (Minimum Requirement)

• All adults born in 1957 or later without documented immunity 1
• All women of childbearing age without rubella immunity, regardless of birth year 1

Two-Dose Recipients (28-Day Minimum Interval)

The following groups require two doses of MMR vaccine spaced at least 28 days apart: 1, 4

• Healthcare personnel born in 1957 or later 1
• Students in post-secondary educational institutions (colleges, universities, vocational schools) 1
• International travelers 1
• Adults in outbreak settings or recently exposed to measles or mumps 1
• Adults who received killed measles vaccine (1963-1967) 1
• Adults who received measles vaccine of unknown type (1963-1967) 1
• Adults vaccinated with mumps vaccine before 1979 who are at high risk 4

Critical timing detail: The minimum interval between doses is 28 days (4 weeks). If a second dose is inadvertently given before 28 days, it must be repeated after the appropriate interval. 4

Absolute Contraindications

MMR vaccine is contraindicated in the following situations: 5

Pregnancy

• MMR is absolutely contraindicated during pregnancy due to theoretical risk of congenital rubella syndrome 5
• However, post-marketing surveillance of 425 women inadvertently vaccinated during pregnancy showed no increase in birth defects or CRS cases 5
• Women should avoid pregnancy for 4 weeks (28 days) after MMR vaccination 1
• Non-immune women should receive MMR immediately after delivery or pregnancy termination, before hospital discharge 1

Severe Immunodeficiency

• Persons receiving immunosuppressive therapy, including high-dose corticosteroids 5
• Persons with severe immunocompromise from any cause 2

Exception for HIV-infected persons: MMR is now recommended for all persons aged ≥12 months with HIV infection who do not have evidence of current severe immunosuppression. 3 Persons with perinatal HIV infection previously vaccinated should be revaccinated with two appropriately spaced doses once effective antiretroviral therapy is established. 3

Post-Exposure Prophylaxis

MMR Vaccine for Post-Exposure Prophylaxis

MMR vaccine administered within 72 hours of measles exposure may provide protection or modify disease severity. 2

• Preferred over immune globulin for most persons aged ≥12 months in outbreak settings 2
• Acceptable for susceptible household contacts aged ≥6 months within 72 hours of exposure 2
• Does not prevent or modify rubella or mumps after exposure 2
• Contraindicated for immunocompromised persons and pregnant women as post-exposure prophylaxis 2

Immune Globulin for Post-Exposure Prophylaxis

Immune globulin (IG) is indicated when MMR vaccine is contraindicated or when exposure occurred >72 hours ago (but <6 days). 2, 3

Standard dosing:

• Immunocompetent persons: 0.25 mL/kg body weight (maximum 15 mL) 2
• Immunocompromised persons: 0.5 mL/kg body weight (maximum 15 mL) 2
• Expanded 2012 recommendation: Infants aged birth to 6 months exposed to measles should receive IGIM 3

IGIV for high-risk groups:

• Severely immunocompromised persons and pregnant women without measles immunity who are exposed should receive intravenous immune globulin (IGIV) 3
• Standard IGIV dose of 100-400 mg/kg is sufficient if given within 3 weeks of exposure 2

Critical timing: IG must be administered within 6 days of measles exposure to be effective. 2

Special Populations and Drug Interactions

Immune Globulin and Blood Product Interactions

Immune globulins and blood products interfere with MMR vaccine response and must not be given concurrently. 5 ACIP provides specific interval recommendations between antibody-containing products and live virus vaccines. 5 If MMR is indicated, administer at least 2 weeks before beginning IGIV therapy. 2

Tuberculin Skin Testing

If tuberculin skin testing with PPD is needed, administer it before MMR vaccination, simultaneously with MMR, or at least 4-6 weeks after MMR. 5 Live attenuated measles, mumps, and rubella vaccines may cause temporary depression of tuberculin skin sensitivity. 5

Other Live Viral Vaccines

MMR can be administered concurrently with other live viral vaccines at different anatomic sites. 5 If not given concurrently, separate MMR from other live viral vaccines by at least one month (28 days). 5

Lactation

MMR vaccination is acceptable during breastfeeding, though rubella vaccine virus may be secreted in breast milk and transmitted to infants. 5 In breast-fed infants with serologic evidence of rubella vaccine strain antibodies, none exhibited severe disease; one exhibited mild clinical illness. 5

Common Pitfalls to Avoid

• Do not accept physician-diagnosed disease as evidence of immunity for any of the three diseases, particularly rubella 2, 3
• Do not assume adults born before 1957 are immune if they are healthcare personnel—they require documentation or vaccination 1
• Do not delay vaccination for serologic testing in most adults—direct vaccination is more efficient 2
• Do not count doses given <28 days apart as valid; the second dose must be repeated 4
• Do not withhold MMR from HIV-infected persons unless they have current severe immunosuppression 3