Titer testing, laboratory evidence of immunity, is available for some vaccines and in some situations.
With titer testing, you do a blood test to check your antibody levels, which can help determine if you are immune to a specific disease, like measles or chicken pox.
Titer testing is sometimes recommended to confirm the immunity status of:
- healthcare workers
- pregnant women – rubella and hepatitis B
- internationally adopted children
- children and adults with lost vaccine records
While not available for all vaccines, like Hib and pertussis, when necessary, you can check titers for MMR, hepatitis A, hepatitis B, diphtheria, tetanus, polio, and varicella.
Should you get titer testing just in case your child is immune from an asymptomatic infection? While it is true that many viruses and bacteria can cause infections without symptoms, it is extremely unlikely that your child would have had a vaccine-preventable disease without symptoms, considering most are at low levels.
Titer testing to avoid a second MMR vaccine is not recommended. Although the second MMR vaccine is technically not a booster shot, if your child is negative to any of the three components of the vaccine, then he will need the second shot.
Is there a downside to vaccine titer testing?
Commercial antibody assays, particularly the LA test, may not be sensitive enough to detect vaccine-induced antibody in some recipients.
Because of the potential for false-negative serologic tests, routine postvaccination serologic testing is not recommended.
Many people who have negative titer tests may still be immune because they have a retained anamnestic potential, instead of being a nonresponder to the vaccine or losing their immunity.
And then there is the pain and cost of doing a blood test. Plus, if titer testing is negative, even if it is a false-negative, you will have to get a vaccine anyway, which is why most doctors and parents opt for getting vaccinated and skipping titer testing unless it is necessary.
For more information:
- Seroconversion after measles or MMR vaccine
- CDC Guidance for Evaluating Health-Care Personnel for Hepatitis B Virus Protection and for Administering Postexposure Management
- Pinkbook – Varicella
- Prevention of Measles, Rubella, Congenital Rubella Syndrome, and Mumps, 2013: Summary Recommendations of the Advisory Committee on Immunization Practices (ACIP)