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For people with Down syndrome, family members, caregivers and professionals.

Antibodies Against Measles

April 2024 | Brian Chicoine, MD - Medical Director, Adult Down Syndrome Center

What is measles?

Measles is a highly contagious viral infection. Due to the availability and effectiveness of vaccines, many individuals have never experienced or even seen measles in the United States and many other parts of the world. Measles vaccine is typically given to children as a 2-shot series. Additional information is available in our Measles and Down Syndrome article.


How does the CDC define evidence of immunity against measles?

According to the Centers for Disease Control and Prevention (CDC), acceptable presumptive evidence of immunity against measles includes at least one of the following:

  • Written documentation of adequate vaccination.

    • One or more doses of a measles-containing vaccine administered on or after the first birthday for preschool-age children and adults not at high risk.

    • Two doses of measles-containing vaccine for school-age children and adults at high risk, including college students, healthcare personnel, and international travelers

  • Laboratory evidence of immunity (blood test)

  • Laboratory confirmation of measles illness (blood test)

  • Birth before 1957


Do adults with Down syndrome need to get a blood test to confirm they are immune to measles?

For many individuals, the answer is “no” if they have been previously immunized against measles. However, blood work to determine immunity (measuring antibodies against measles) in adulthood may be recommended for some individuals depending on where they work, where they go to school, and how many vaccines for measles they have received in the past. In these situations, additional vaccines may be recommended. If the blood tests do not show immunity, additional vaccines also may be recommended.

Health care

You may be required to get blood tests to see if you are immune to measles (and/or additional measles vaccine) if you work in a health care setting. For these occupations, your employer may request that you get a blood test to demonstrate immunity against measles and, if not immune, that you get an additional dose or doses of measles vaccine. In health care settings, employers are very careful with measles immunity for their employees who work with patients. A hospital employee who is not immune to measles and develops measles illness could expose many patients who have impaired immunity and, therefore, are at greater risk for developing measles.

Post-high school education settings

For students at a post-high school education setting, a second dose is recommended if only one dose was given in childhood. Blood testing is not typically recommended in this situation.

International travel

If you are traveling internationally, a second dose is recommended if you only had one in childhood. Blood testing is not usually recommended in this situation. 

Measles outbreaks

If there is a measles outbreak, public health authorities may determine that some individuals are at increased risk and, thus, recommend an additional dose or doses. Blood testing may be recommended. However, waiting for blood test results may not be recommended if there is a need to improve immunity quickly. Therefore, in this situation, an additional vaccine without blood testing may be recommended.


The blood test to check for immunity against measles is called measles immunity test IgG or measles IgG. It may also be called Rubeola IgG. Rubeola is the other name for measles. (This is different than Rubella, which is German Measles).


Why would antibodies be low even though immunizations were given in childhood?

Immunity may wane over time – i.e., we are no longer immune to the illness that we were immunized against. Sometimes there is still immunity but not enough antibodies to be measured to be positive for immunity on the blood test. Depending on the situation, if the test is negative for immunity, additional vaccine may be recommended.


Is this typical in adults with Down syndrome?

Although it is not something we routinely test for, theoretically, loss of immunity in adults with Down syndrome is something that might occur more frequently because immune dysfunction is more common in people with Down syndrome. However, we have not seen a case of measles in our patients nor are we aware of any data indicating that measles infection occurs with a high enough frequency or more frequently in people with Down syndrome to warrant recommendations different than the rest of the population. Therefore, routine testing or re-immunization in otherwise healthy adults with Down syndrome is not recommended other than in the situations noted above.


Additional information is available on the CDC website opens in new window.

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Please note: The information on this site is for educational purposes only and is not intended to serve as a substitute for a medical, psychiatric, mental health, or behavioral evaluation, diagnosis, or treatment plan by a qualified professional. We recommend you review the educational material with your health providers regarding the specifics of your health care needs.