Screening for Rubella Immunity
Screening for rubella immunity is accomplished by ordering serologic studies (Option B), as vaccination history alone is unreliable and laboratory confirmation of rubella IgG antibody is the only definitive evidence of immunity. 1, 2
Why Serologic Testing is the Gold Standard
Laboratory evidence of rubella IgG antibody is the only reliable proof of immunity, as clinical diagnosis and vaccination history are both unreliable indicators of immune status. 1
Any antibody level above the standard positive cutoff value of a licensed assay can be considered evidence of immunity. 1
The most commonly used serologic assays include enzyme immunoassays (EIAs), with other options including latex agglutination, immunofluorescence assay (IFA), passive hemagglutination, hemolysis-in-gel, and virus neutralization tests. 1
Why Vaccination History Alone is Insufficient
Vaccination history has poor diagnostic value for determining rubella susceptibility, with a sensitivity of only 54.4% and specificity of 69.3% in identifying disease susceptibility. 3
Even among women with documented vaccination history, 7.8% were found to be non-immune upon serologic testing. 3
Self-reported vaccination history or parental reports are not considered adequate documentation and should not be relied upon for determining immunity. 1
When Serologic Screening Should Be Performed
Prenatal screening should be carried out on all pregnant women not known to be immune, as this is critical for preventing congenital rubella syndrome. 1, 4
Serologic screening is most appropriate when persons identified as susceptible can be subsequently vaccinated in a timely manner (e.g., during hiring of healthcare workers). 1
During outbreak situations, serologic screening before vaccination is generally not recommended, as waiting for results can impede rapid vaccination needed to control the outbreak. 1
Special Considerations for Women of Childbearing Age
Birth before 1957 is NOT acceptable evidence of rubella immunity for women who can become pregnant, as this provides only presumptive evidence and does not guarantee immunity. 1, 2
For non-pregnant women without documented immunity, direct vaccination with MMR without serologic testing may be preferable when costs of serology are high and follow-up for vaccination cannot be assured. 1
Management of Indeterminate Results
Persons with "equivocal" or "indeterminate" serologic test results should be considered susceptible to rubella unless they have documentation of adequate vaccination or subsequent testing demonstrates immunity. 1, 2
These individuals should be vaccinated immediately with MMR vaccine without repeat serologic testing, as this is more cost-effective and ensures protection. 2