Background: There are very few reports of anaphylactic reactions to yellow fever (YF) vaccine in the literature, and these date from the 1940s.
Objective: We sought to estimate the rate of YF vaccine-related anaphylaxis.
Methods: All reports of adverse reactions to YF vaccine submitted to the Vaccine Adverse Event Reporting System between 1990 and 1997 were reviewed for those meeting criteria for probable or possible anaphylactic reactions.
Results: Of 243 reports submitted, 40 describe probable or possible anaphylactic reactions. In 22 of these 40, YF vaccine was the only vaccine administered. There were 5,236,820 doses of YF vaccine distributed in the United States during this period. By using all 40 cases, the rate of YF vaccine-related anaphylaxis would be 40 in 5, 236,820 or about 1 in 131,000. In 35 of the reports, information was provided on whether previous doses of YF vaccine had been given. In 34 of these 35, the reaction occurred after the first dose of YF vaccine, suggesting that vaccine constituents other than the viral proteins may have been the allergens. The vaccine is grown in chicken embryos and contains gelatin as a stabilizer.
Conclusion: YF vaccine can cause anaphylactic reactions. Persons presenting for YF vaccine should be asked if they have had adverse reactions to previous doses of this or other vaccines and if they are allergic to eggs, chicken, or gelatin. Health care workers administering YF vaccine should be prepared to recognize and treat anaphylactic reactions should they occur.