Vaccine Allergies - Managing Your Allergies: Allergies

Content provided by the Faculty of the Harvard Medical School

Vaccine allergies

Understandable concerns swirl about allergic reactions to vaccines. But it’s important to tease the truth out of the rumors. Vaccines are a category of drug allergy, but here the drug is administered to healthy people, the majority of whom are babies, to protect them from specific infectious diseases. As such, vaccine reactions are vigilantly monitored.

Allergic reactions to vaccines are very rare — about one in a million — but fatal anaphylactic reactions have been reported. On the other hand, if you’re undecided about whether to vaccinate your child or yourself, you need to weigh the high-risk consequences of not vaccinating. Any parent considering withholding immunization must consider the documented risk for life-threatening diseases such as measles and mumps, in unvaccinated children. In addition, to attend school, a child is typically required to have certain vaccinations.

While anything in a vaccine could theoretically cause a reaction, the two big culprits are the additives gelatin and egg protein. Gelatin is added to a number of vaccines — the measles, mumps, and rubella (MMR); varicella; and Japanese encephalitis vaccines. Egg protein can be found in the yellow fever and flu vaccines. The preservative thimerosal, which triggers allergic reaction in some people, is no longer included in U.S.-licensed vaccines.

The vaccine that probably causes parents the most concern is the MMR vaccine because it is grown in a chicken-derived culture. Studies have suggested that any reaction to the vaccine is because of the gelatin and not the egg connection. But studies have also shown that the MMR vaccine can be given to babies who are allergic to eggs with very low risk for a serious reaction. And protocols have been developed to administer flu vaccines to egg-allergic people.

Last updated:	August 21, 2006
Reviewed By:	Faculty of Harvard Medical School