How do I confirm immunity to Measles, Mumps, and Rubella (MMR)?

Confirming MMR Immunity: Laboratory Testing Approach

Order serologic testing for IgG antibodies to measles, mumps, and rubella using any standard, licensed enzyme immunoassay (EIA), and consider any antibody level above the positive cutoff value as evidence of immunity. 1

Laboratory Testing Specifications

For measles immunity:

• Positive measles IgG antibody detected by any standard serologic test confirms immunity 2, 3
• Modern enzyme immunoassays (EIA/ELISA) have replaced older hemagglutination-inhibition (HI) tests and offer superior sensitivity 2

For mumps immunity:

• Demonstration of mumps IgG antibody by any commonly used serologic assay confirms immunity 1

For rubella immunity:

• Positive rubella IgG antibody confirms immunity 2, 1
• The only reliable evidence of previous rubella infection is the presence of serum rubella IgG 2

Critical Interpretation Guidelines

Handling equivocal results:

• Persons with "equivocal" serologic test results should be considered susceptible unless they have documented age-appropriate vaccination or subsequent testing confirms immunity 2, 3

Important caveat for healthcare personnel:

• For healthcare workers with documented MMR vaccination who test negative or equivocal, the documented age-appropriate vaccination supersedes the serologic results—they should still be considered immune 1
• Do not administer additional vaccine doses based on negative serology alone if proper vaccination is documented 1

When to Order Titers vs. Vaccinate

Cost-effectiveness considerations:

• Serologic screening is not necessary before vaccinating unless the medical facility considers it cost-effective 2, 1
• Serologic testing is appropriate only if persons identified as susceptible will be subsequently vaccinated in a timely manner 2
• During outbreaks, serologic screening before vaccination is not recommended because rapid vaccination is necessary to halt disease transmission 2

Alternative Evidence of Immunity (Non-Laboratory)

If documentation is available, laboratory testing may not be necessary:

• Measles: Written documentation of 2 doses of live measles or MMR vaccine administered at least 28 days apart 1
• Mumps: Written documentation of 2 doses of live mumps or MMR vaccine administered at least 28 days apart 1
• Rubella: Written documentation of 1 dose of live rubella or MMR vaccine 2, 1
• Birth before 1957 provides presumptive evidence (except for rubella in women of childbearing age) 2

Common Pitfalls to Avoid

• Do not use IgM testing for immunity assessment—IgM is only for acute infection diagnosis, not immune status 3, 4
• Do not rely on clinical diagnosis—physician-diagnosed disease is no longer acceptable evidence of immunity for measles and mumps 5
• Do not assume birth before 1957 guarantees immunity—approximately 4-10% of healthcare personnel born before 1957 lack measles IgG antibodies 1, 3
• Do not repeat vaccination based solely on negative titers if proper documentation exists—documented vaccination takes precedence over serology in healthcare workers 1