What titer tests are recommended for adults working in a daycare setting to assess immunity against measles, mumps, rubella (MMR), and varicella (chickenpox)?

Titer Testing for Adults Working in Daycare Settings

For adults working in daycare, order serologic testing (titers) for measles IgG, mumps IgG, rubella IgG, and varicella IgG if vaccination documentation is unavailable or uncertain. 1, 2

When to Order Titers vs. Direct Vaccination

Prevaccination serologic screening is not necessary if it is more cost-effective to simply vaccinate, as the vaccines are safe even in immune individuals 1. However, many employers prefer documentation of immunity through titers for liability and outbreak management purposes.

Evidence of Immunity Without Titers

Adults can demonstrate immunity without serologic testing if they have: 1

• MMR: Documentation of 2 doses of MMR vaccine given at least 28 days apart after the first birthday 1, 3
• Varicella: Documentation of 2 doses of varicella vaccine given 4-8 weeks apart 2
• Birth before 1957: Generally considered immune to measles, mumps, and rubella (but NOT for women of childbearing age regarding rubella) 1

Specific Titer Tests to Order

For Measles, Mumps, and Rubella

• Order: Measles IgG antibody, Mumps IgG antibody, Rubella IgG antibody 1
• Testing method: Enzyme immunoassay (EIA) or ELISA are preferred over older hemagglutination-inhibition (HI) tests 1
• Interpretation: Any detectable antibody indicates immunity 1

For Varicella

• Order: Varicella-zoster virus (VZV) IgG antibody 1, 2
• Note: Approximately 90% of US-born adults are already immune to varicella 1

Critical Considerations for Daycare Workers

Daycare employees are specifically highlighted as high-priority for varicella vaccination due to their work environment where transmission is likely 1, 2. They should receive special emphasis for ensuring immunity to all four diseases.

Managing Equivocal Results

• Equivocal titer results should be treated as susceptible unless other evidence of immunity exists 1
• Do not repeat titers or give additional vaccine doses if someone with documented 2-dose MMR vaccination tests negative or equivocal—documented vaccination supersedes serologic results 1

Common Pitfalls

• Physician-diagnosed disease is NOT acceptable evidence of immunity for rubella (unlike measles and mumps) 1, 3
• Women of childbearing age cannot rely on birth before 1957 as evidence of rubella immunity—they require either vaccination documentation or positive serology 1
• Clinical diagnosis of rubella is unreliable and should never be used to assess immune status 1

Vaccination After Negative Titers

If titers are negative or equivocal:

• MMR: Administer 1-2 doses depending on risk (daycare workers should receive 2 doses, 28 days apart) 1, 3, 4
• Varicella: Administer 2 doses, 4-8 weeks apart 2, 5
• Women should avoid pregnancy for 4 weeks after MMR or varicella vaccination 2, 3, 4