Consultations & Comments: Any Need for Dose 3 of MMR Vaccine?

If a patient has had 2 appropriately administered doses of measles-mumps-rubella (MMR) vaccine and has a nonimmune response on a rubella titer (required in all pregnant women in Louisiana), should another dose of MMR vaccine be given? Is there any evidence that this would provide immunity to rubella?

- Robert P. Blereau, MD
   Morgan City, La

The Advisory Committee on Immunization Practices (ACIP) does not recommend more than 2 doses of MMR vaccine for anyone. In fact, the ACIP defines rubella immunity as either a positive serologic test result or one documented dose of rubella vaccine on or after the first birthday. Seroconversion following a single dose of rubella vaccine is 95%. Seroconversion after 2 doses is greater than 99%. The likelihood of a person's truly being susceptible after 2 doses of MMR vaccine is very remote, and the negative serologic result you report is most likely a false-negative. We encounter this issue frequently with commercial screening tests.

To my knowledge, there are no data on the administration of more than 2 doses of MMR. I suggest you do nothing. If you must take action on this for some programmatic reason (a school requirement, for instance), then in my opinion, you can give another dose. This will not be harmful, since the person is already immune. However, I do not recommend further serologic testing in such a patient.

- William L. Atkinson, MD, MPH
   National Immunization Program
   Centers for Disease Control
      and Prevention
   Atlanta