Laboratory Evidence of Measles Immunity

Acceptable Laboratory Evidence

• The Centers for Disease Control and Prevention (CDC) defines laboratory evidence of measles immunity as a positive measles IgG antibody detected by any standard serologic test 1, 2
• Any antibody level above the standard positive cutoff value of a licensed assay can be considered evidence of immunity, according to the CDC's Advisory Committee on Immunization Practices (ACIP) 3, 4
• Persons with positive measles IgG by any serologic test are considered immune by the CDC 3

Important Caveats About Equivocal Results

• The CDC considers persons with "equivocal" serologic test results to be susceptible to measles unless they have other evidence of immunity, such as documented vaccination or birth before 1957 3, 4

Clinical Context and Testing Considerations

• Approximately 4-10% of healthcare personnel lack measles IgG antibodies, even among those born before 1957 who are presumed immune by age, highlighting the importance of laboratory confirmation by the CDC 1, 2
• IgM antibody testing is used for acute measles diagnosis, not for determining immunity status, as stated by the CDC 5
• IgG antibody testing is the appropriate test for determining immune status, according to the CDC 1, 2

Alternative Evidence of Immunity (Non-Laboratory)

• The CDC accepts documentation of two doses of live measles vaccine administered on or after the first birthday as evidence of immunity 1
• Birth before 1957 is considered presumptive evidence of immunity by the CDC 3, 4