Bad Reaction No Good Reason to Avoid Future Shots

THURSDAY, Oct. 15 (HealthDay News) -- People who appear to be allergic to vaccinations shouldn't automatically avoid future immunizations, but instead should try to find out why they had a bad reaction, new guidelines say.

"Local, injection-site reactions and constitutional symptoms, especially fever, are common after vaccinations and do not contraindicate future doses," Dr. John M. Kelso, of the Division of Allergy, Asthma & Immunology at Scripps Clinic in San Diego, Calif., and a chief editor of the guidelines, explained in a news release from the American College of Allergy, Asthma & Immunology.

The guidelines are published in the October issue of Annals of Allergy, Asthma & Immunology.

An estimated 235 million vaccine doses are administered in the United States each year, and only about 235 people suffer a serious allergic reaction known as anaphylaxis, according to background information from the college. Deaths are extremely rare.

Kelso and his colleagues suggest that medical officials report all serious reactions to the Vaccine Adverse Event Reporting System so that experts can try to figure out what caused the reaction.

The guideline authors also recommend that allergists investigate allergic reactions and perform allergy testing to determine the cause and best treatment.

According to the researchers, the active ingredients within vaccines don't typically cause allergic reactions. Instead, sickness usually stems from other components, such as gelatin, egg protein and, more rarely, yeast, neomycin and thimerosal, as well as latex in immunization equipment.

"Gelatin, which is added to many vaccines as a stabilizer, is either bovine or porcine, which are extensively cross-reactive," Kelso said. "We recommend that a history of allergy to the ingestion of gelatin should be sought before administering a gelatin-containing vaccine."

"The MMR [measles, mumps, rubella vaccines] and one type of rabies vaccine contain negligible or no egg protein and can be administered to egg-allergic children without prior skin testing," he added. "Egg protein is present in higher amounts in yellow fever and influenza vaccines and may cause reactions in egg-allergic patients, who should be evaluated by an allergist prior to receiving these vaccines."

"However rare, if a patient gives a history of an immediate-type reaction to yeast, latex, neomycin or thimerosal, we recommend that it be investigated with skin testing before immunization with a vaccine containing these constituents," he said.

-- Randy Dotinga

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SOURCE: American College of Allergy, Asthma & Immunology, news release, Oct. 8, 2009