How do I order a measles‑mumps‑rubella (MMR) immunoglobulin G (IgG) titer for a patient with unknown immunity status (e.g., pregnant woman, health‑care worker, student, or during an outbreak)?

How to Order MMR Titer

Order a measles-mumps-rubella IgG antibody panel through your laboratory, but in most clinical scenarios you should vaccinate immediately without waiting for serologic results unless you have a cost-effective screening program with guaranteed follow-up. 1, 2

When Serologic Testing is Appropriate

Serologic screening before vaccination should only be performed when:

• Your facility has a cost-effective screening program already established 3, 4
• You can reliably vaccinate identified susceptible persons in a timely manner 3, 4
• You are screening healthcare workers during the hiring process (not during an outbreak) 4

During outbreaks, skip serologic testing entirely because the need to screen, wait for results, and then contact susceptible persons impedes the rapid vaccination needed to control transmission. 1

Laboratory Test Specifications

When serologic testing is indicated, order:

• Measles IgG antibody (enzyme immunoassay is most common) 4
• Mumps IgG antibody (enzyme immunoassay) 4
• Rubella IgG antibody (enzyme immunoassay or hemagglutination inhibition assay) 4

Any antibody level above the standard positive cutoff value of a licensed assay constitutes evidence of immunity. 4

Interpreting Results

Positive (Immune)

• No vaccination needed for that specific component 4
• Document as acceptable evidence of immunity 1, 2

Negative (Susceptible)

• Vaccinate immediately with MMR 2, 3
• Healthcare workers and high-risk groups need 2 doses separated by at least 28 days 1, 2, 3

Indeterminate or Equivocal

Critical pitfall: Treat indeterminate results as non-immune and vaccinate immediately without repeat testing. 4 Do not delay vaccination to retest—this is a common error that leaves patients unprotected.

Special Population Considerations

Pregnant Women

• Never vaccinate during pregnancy (absolute contraindication) 4, 5
• Order rubella IgG titer as part of routine prenatal screening 4, 6
• If non-immune, vaccinate immediately postpartum before hospital discharge 1, 2, 5
• Counsel to avoid pregnancy for 3 months after vaccination 4

Healthcare Workers

• Birth before 1957 does not exempt healthcare personnel from immunity documentation requirements 1, 2, 3
• Require 2 documented MMR doses or laboratory evidence of immunity regardless of birth year 1, 2, 3
• If exposed to measles before vaccination, exclude from work days 5-21 after exposure 3

Students in Post-Secondary Education

• Require 2 documented MMR doses or laboratory evidence of immunity 1, 2
• During outbreaks, vaccinate immediately without serologic testing 1

International Travelers

• Require 2 documented MMR doses before travel 1, 2
• Consider vaccination without serologic testing given time constraints 1

Cost-Effectiveness Considerations

The direct vaccination approach (without serologic testing) is generally more cost-effective when:

• Serology costs are high 4
• Follow-up for vaccination cannot be assured 4
• Rapid protection is needed (outbreak settings) 1, 3

Screening may be cost-effective only in established programs during routine healthcare worker hiring. 3, 4

Common Pitfalls to Avoid

• Do not accept self-reported vaccination history as adequate documentation of immunity 4
• Do not accept physician-diagnosed disease as evidence of immunity (laboratory confirmation required) 1, 7
• Do not assume birth before 1957 equals immunity for healthcare workers or women of childbearing age 1, 2, 3, 4
• Do not delay vaccination while waiting for serologic results in outbreak settings 1, 3
• Do not repeat testing for indeterminate results—vaccinate immediately instead 4

Practical Algorithm

1. Determine patient category: Healthcare worker, pregnant woman, student, international traveler, or general adult 1, 2

2. Check documentation: Look for written record of 2 MMR doses (for high-risk groups) or 1 dose (general adults born ≥1957) 1, 2

3. If no documentation exists:

   • High-risk groups or established screening programs: Order MMR IgG panel 3, 4
   • All other scenarios: Vaccinate immediately without testing 3, 4

4. If testing is performed and results are non-immune or indeterminate: Vaccinate immediately (confirm not pregnant first) 2, 3, 4

5. Schedule second dose 28 days later for healthcare workers, students, and international travelers 1, 2, 3