What test should I use to determine measles immunity?

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Measles Immunity Testing

Use enzyme immunoassay (EIA/ELISA) to measure measles-specific IgG antibodies as the primary test for determining measles immunity, as this has supplanted older hemagglutination inhibition (HI) testing and is the most commonly used commercial assay available today. 1

Recommended Testing Approach

First-Line Test: Measles IgG by EIA/ELISA

  • Any licensed EIA showing antibody levels above the standard positive cutoff value is considered evidence of immunity 1
  • EIAs have equal or greater sensitivity compared to the older HI test and are now the most commonly used commercial assays 1
  • The test requires only a single serum sample and provides straightforward positive/negative results 1

Alternative Acceptable Methods

Other commercially available assays that can detect measles immunity include: 1

  • Latex agglutination
  • Immunofluorescence assay (IFA)
  • Passive hemagglutination
  • Hemolysis-in-gel
  • Virus neutralization tests (plaque reduction neutralization/PRN test)

Critical Interpretation Considerations

Understanding Test Sensitivity Differences

  • When adults who appeared antibody-negative by older HI testing were retested with more sensitive assays like EIA, almost all (>95%) had detectable antibodies 1
  • Children who "lost" detectable HI antibodies over 16 years of follow-up almost all retained antibodies detectable by more sensitive tests 1
  • This confirms that modern EIA testing is superior for detecting vaccine-induced immunity 1

Important Caveats for EIA Testing

Be aware that current commercial EIAs have limitations in detecting vaccine-induced immunity: 2

  • Approximately 10% of healthcare workers with documented vaccination history and protective neutralizing antibody levels (PRN >120 mIU/mL) tested falsely negative on commercial EIAs 2
  • This false-negative rate increased to 19% among persons born 1975-1985, representing the early measles vaccination period 2
  • When 154 healthcare workers were tested, 99.4% had protective antibody levels by neutralizing test, but commercial EIAs missed approximately 10% 2

When Neutralizing Antibody Testing May Be Preferred

Consider plaque reduction neutralization (PRN) testing as the gold standard when: 2

  • Assessing vaccine-induced immunity in healthcare workers or other high-risk populations
  • EIA results are equivocal or negative despite documented vaccination history
  • Determining true protective immunity rather than just antibody presence
  • PRN >120 mIU/mL is considered protective 2

Clinical Algorithm for Equivocal Results

If a person with documented measles vaccination history has borderline or negative IgG by ELISA: 1

  • Administer one dose of MMR vaccine
  • Do not retest for serologic evidence of immunity
  • This approach is more practical than pursuing additional serologic testing 1

Confirming Immunity After Revaccination

  • In persons with initially undetectable antibodies who receive revaccination, immunity can be confirmed by documenting a booster response (absence of IgM with rapid rise in IgG) 1

Practical Recommendations by EIA Titer Ranges

Based on correlation studies between EIA-IgG and protective antibody levels: 3

  • EIA-IgG ≥12.0: Person is protected against measles
  • EIA-IgG 8.0-12.0: May benefit from booster vaccination
  • EIA-IgG 4.0-8.0: Insufficiently protected, requires booster dose

Key Pitfalls to Avoid

False-Positive IgM Results

  • As measles becomes rare, false-positive IgM results increase significantly in low-prevalence settings 4
  • IgM testing is NOT appropriate for routine immunity screening—only use IgG 1
  • If IgM is detected without epidemiologic linkage to confirmed measles, perform confirmatory testing with direct-capture IgM EIA method 4

Test Selection Based on Clinical Context

  • Do not use hemagglutination inhibition (HI) testing, as it has been supplanted by more sensitive assays 1
  • Commercial EIAs are adequate for most clinical purposes but may miss some vaccine-induced immunity 2
  • Reserve neutralizing antibody testing (PRN) for research purposes or when precise determination of protective immunity is critical 2

Timing Considerations

  • Measles IgG persists lifelong after natural infection or successful vaccination 1
  • No specific timing requirements for IgG testing relative to vaccination or exposure 1
  • Vaccine-induced antibody levels may decline over time but this does not indicate loss of protection 1

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Research

Immune status of health care workers to measles virus: evaluation of protective titers in four measles IgG EIAs.

Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology, 2015

4
Guideline

SSPE Pathogenesis and Risk Factors

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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