Measles Immunity Testing
Order a Measles IgG Antibody Test by Enzyme Immunoassay (EIA/ELISA)
The CDC recommends ordering a measles-specific IgG antibody test using enzyme immunoassay (EIA/ELISA) as the primary and preferred method to determine measles immunity. 1, 2, 3
Why EIA/ELISA is the Correct Test
EIA/ELISA has supplanted older hemagglutination inhibition (HI) testing and is now the most commonly used commercial assay available, with equal or greater sensitivity compared to the outdated HI test. 4, 1
Any antibody level above the standard positive cutoff value of a licensed EIA is considered evidence of immunity—the test provides straightforward positive/negative results requiring only a single serum sample. 1, 2, 3
Modern EIA testing is superior for detecting vaccine-induced immunity: when adults who appeared antibody-negative by older HI testing were retested with EIA, almost all (>95%) had detectable antibodies. 1
Interpreting Results
Positive Result
Equivocal or Negative Result in Vaccinated Persons
If a person with documented measles vaccination history has borderline or negative IgG by ELISA, administer one dose of MMR vaccine and do not retest for serologic evidence of immunity—this approach is more practical than pursuing additional serologic testing. 1, 2
For healthcare workers with documented age-appropriate vaccination who test negative or equivocal, the documented vaccination supersedes the serologic results and they should still be considered immune. 2
Equivocal Result Without Vaccination History
- Persons with "equivocal" serologic test results should be considered susceptible to measles unless they have other evidence of immunity (such as documented vaccination or birth before 1957). 2, 3
Critical Pitfalls to Avoid
Do NOT order measles IgM testing for immunity screening—IgM is only appropriate for diagnosing acute measles infection, not for determining immune status. 1, 3, 5, 6
Do NOT use hemagglutination inhibition (HI) testing, as it has been supplanted by more sensitive EIA assays and frequently fails to detect residual immunity. 1, 7
Do not order titers for persons with documented age-appropriate vaccination unless your medical facility considers it cost-effective, as vaccination records alone are acceptable evidence of immunity. 2
Alternative Commercially Available Assays
While EIA/ELISA is preferred, other licensed assays that can detect measles IgG immunity include:
- Latex agglutination 1
- Immunofluorescence assay (IFA) 1, 8
- Hemolysis-in-gel 1
- Virus neutralization tests 4
However, EIA/ELISA remains the most practical and widely available option. 1
Clinical Context
Measles IgG persists lifelong after natural infection or successful vaccination, with no specific timing requirements for testing relative to vaccination or exposure. 1, 9
Vaccine-induced antibody levels may decline over time, but this does not indicate loss of protection—ELISA antibodies remain detectable in 95-100% of individuals 11-13 years after primary vaccination. 9
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 when immunity documentation is needed. 2, 3