Ask Dr. Sears: Test to Determine Immunities to Diseases

Ask Dr. Sears: Test to Determine Immunities to Diseases 1Please welcome Dr. Bob Sears back to Metropolitan Mama.

Sears is a nationally known pediatrician, father of three, and author of The Vaccine Book: Making the Right Decision for Your Child. Sears has graciously offered to extend his expertise about vaccines through a bimonthly column where YOU ask the questions…and he answers them. See the bottom of this post for details about how you can submit a question.

If you want more information now, you should really just buy his book (read my review here). It’s comprehensive, objective, and the only one of its kind on the market.

Today’s question was sent in by Jen.

QUESTION: "I have a friend who says that there is a test that children can take to determine what immunities are already in their systems and, therefore, if particular vaccines are unnecessary. What test is it that kids can take and is this recommended?"

ANSWER FROM DR. SEARS: These blood tests are called "titers." They can determine if a person has been exposed to a disease and has good immunity (as with chickenpox, for example). They can also measure how much immunity a person has gained after one or more doses of a vaccine.

Overall, titers aren't really practical during infancy or toddlerhood for many vaccines for a variety of reasons (mainly because of the cost and the trouble of blood tests). But here are a few examples of when titers can be useful:

  1. If parents skip any vaccines in the early years, but wish to consider getting some vaccines at a later age, I recommend checking titers for measles, mumps, rubella, and Hep A around age 10. If these titers show immunity, you wouldn't need the shot.
  2. If parents skip some shots, but state laws or other requirements mandate that they either get the shots or prove immunity to the disease, titers can be done to demonstrate the immunity.
  3. If a child had one dose of MMR or Chickenpox vaccine during infancy, but the parents are considering skipping (or delaying) the 5 year boosters, titers can be checked to see whether or not the child still has enough immunity from the first shot.

These are really the only situations where I would consider getting titer tests. One particular approach that I don't recommend parents trying is checking titers after 1 or 2 doses of a 4-dose series of any particular shot. Some parents will do this (for example, check Pertussis and Tetanus immunity after 2 doses of the DTaP shot) to see if the rest of the shots in the series are needed. I don't think this is practical. Most kids won't show great immunity after just 2 doses anyway, and those that do would probably see their immunity wear off several months later anyway (which you wouldn't even know unless you check ANOTHER titer) because they didn't finish the series.

Ask Dr. Sears: Test to Determine Immunities to Diseases 2For more information, see The Vaccine Book: Making the Right Decision for Your Child, or visit


If you have a question about vaccines for Dr. Sears, send an e-mail with “Ask Dr. Sears” in the subject line to [email protected].

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8 comments on “Ask Dr. Sears: Test to Determine Immunities to Diseases”

  1. I have two children who ate ages 9 and 8. They have received no vaccines, ever. For children in this situation what would the blood titers test provide or prove? Obviously there would be no immunity to the vaccines. Would this test then show natural immunities only. Would this be a useful test at all for unvaccinated children?

  2. I'm very interested in this series! We havne't vaccinated yet, not to say that we won't EVER, and this post is exactly the information I was hoping to read about the topic. Thank you Dr Sears!!!

  3. I second, great info!! I've heard such great things about the vaccination book - it's on my 'to buy' list. Thanks for the Q&A.

  4. Stephanie -

    Thanks so much for these great posts about vaccinations! I have Dr. Sears' book on reserve at the library and don't know if I can keep waiting for it. I think I'm just going to buy a copy for myself. We vaccinated our daughter up to age 1 (she's 2 now), and decided to stop. Our decision was complex, and not taken lightly, and largely hinged on the variety of other medical conditions she struggles with and some suspected reactions following the vaccinations she did. I plan to blog about our experiences and vaccination decision in the near future. It's a controversial and often polarizing topic that I think deserves more discussion. I'm glad that more parents are looking objectively at the research out there and evaluating the pros and cons of each side. It's a decision that should be fully informed.

  5. I am so amazed at the amount of information we have now on vaccines versus when we had them as a child. It was basically no questions asked and just do it. Now, parents are researching more and questioning the use of each vaccine. Basically not assuming anything anymore, whcih is a good thing. Thanks Stephanie for the post!

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