Serology testing
Health care providers may encounter requests from employers, colleges or universities for serologic testing (titre) to assess immunity. These institutions set their own requirements, and may require both proof of immunization and serology.
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.
According to the Canadian Immunization Guide, routine serologic testing to determine the immunity of children and adults without immunization records is generally not practical. Individuals who report incomplete immunization or lacking adequate documentation of immunization should be considered unimmunized and started on an immunization schedule appropriate for their age and risk factors.
If a patient has a completed a valid vaccination series for measles, mumps, rubella, varicella or hepatitis B, serology is generally not recommended except in the following situations:
Indications for serology
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.
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 patients without documented evidence of immunization should be serologically screened
- Patients who were properly immunized either before pregnancy or after pregnancy do not need serologic screening in later pregnancies
- Patients 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
Additional resources
Learn more about serological testing for each disease in the Canadian Immunization Guide: