Serology Testing for Guiding Decisions to Vaccinate
Serology is an unreliable indicator of immunity.
The presence of circulating antibodies is generally a poor correlate of immunity.
Serologic titres shortly after vaccination generally indicate an immune response was achieved.
Titres may become undetectable over time, but this does not indicate a loss of immunity. Immune memory usually maintains the ability to mount an immune response if challenged.
If a patient has a completed and valid vaccination series for measles, mumps, rubella, varicella or hepatitis B, serology is generally not recommended except in the following situations:
Indications for serology
Measles
- If there is no history of vaccination or disease, serological testing may be considered
- Previously vaccinated individuals are likely to be immune to measles even if there is no detectable antibody. Re-immunization is not recommended.
Rubella
- Pregnant women without documented evidence of immunization should be serologically screened
- Women who were properly immunized either before pregnancy or after pregnancy do not need serologic screening in later pregnancies
- Women with serologic evidence of immunity in one pregnancy do not need repeat screening in future pregnancies
Varicella
- Certain immunocompromised individuals who are vaccinated with univalent varicella vaccine may have antibody testing six to eight weeks after the last dose
- Previously vaccinated individuals are likely to be immune to varicella even if there is no detectable antibody. Re-immunization is not recommended.
Hepatitis B
- Post-immunization serologic testing is recommended only for certain high-risk groups. Testing must be completed one to six months after the final dose of the series. High-risk groups include the immune compromised, dialysis patients, those with chronic kidney disease and those with high risk of exposure to hepatitis B virus.
Additional resources
Learn more about serological testing for each disease in the Canadian Immunization Guide:
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