Serological testing for immunity to rubella is only recommended before or after receiving rubella-containing vaccine in certain circumstances

Rubella serological assays

Commercial assays for testing immunity to rubella vary according to the method used to determine the positive cut-off value. Antibody levels found by a licensed assay to be above the standard positive cut-off for that assay can be considered evidence of past exposure to rubella virus.⁹

Interpreting serological results

Rubella vaccine induces immune responses that are similar in quality, but lesser in quantity, than responses after natural disease.⁸ Measuring antibody levels by commercial assays is not a perfect correlate of protection in vaccinated people.⁸ Although people with low levels of vaccine-induced antibodies are often protected, some people with measurable antibodies can be reinfected.

If a person is rubella IgG seronegative, they should receive rubella-containing vaccine according to the relevant recommendations. 

Further testing and vaccination is not usually needed for people who remain seronegative after 2 doses. When interpreting serological testing results, it may be useful to discuss the results with the laboratory that performed the test, to ensure that decisions are based on all relevant clinical information.

Negative serology after 2 documented doses of rubella-containing vaccine may be a false negative (that is, an antibody titre too low to be detected using routine commercial assays). If there is difficulty interpreting results, consult experts or refer the sera to a reference laboratory, particularly for women of child-bearing age. See Women of child-bearing age who are seronegative for rubella are strongly recommended to receive rubella-containing vaccine.

Advise all women of child-bearing age of the result of their antibody test, because it is a clinically significant test.

Screening pregnant women for rubella antibodies

All women who are planning pregnancy or have recently become pregnant should be screened for rubella antibodies, irrespective of a previous positive rubella antibody result.^8,10 Women found to be seronegative for rubella immunity during antenatal testing should receive rubella-containing vaccine after delivery and before discharge from the maternity unit. These women should be tested for rubella immunity 6–8 weeks after vaccination.⁹

Very occasionally, patients who are seronegative may be reported as seropositive due to error. Specimens from pregnant women need to be stored for 12 months to allow for parallel serological testing if required.¹¹