The preparation of recombinant
hepatitis B vaccines involves using cellular cultures of Saccharomyces cerevisiae, otherwise known as baker's yeast. Prior to
vaccine licensure, clinical trials were performed to address whether residual
yeast proteins in the
vaccines could induce
anaphylaxis, including testing for
IgE anti-yeast antibody levels. 1-2% of subjects had anti-yeast
IgE antibodies before immunization, but demonstrated no significant rise in
IgE after HBV. We searched reports in the
Vaccine Adverse Event Reporting System (VAERS) for those that mentioned a history of
allergy to yeast and then reviewed the adverse events described in these reports for potential
anaphylactic reactions. Probable
anaphylaxis was defined as the presence of one or more dermatologic symptoms and one or more respiratory, gastrointestinal, or cardiovascular symptoms with onset within 4 h of
Hepatitis B vaccination. Possible
anaphylaxis was defined in one of two ways: (1) cases that described dermatologic or respiratory symptoms (but not both) occurring within 4h of vaccination; or (2) cases that described one or more dermatologic and/or respiratory symptoms occurring 4-12 h post vaccination. Among the 107 reports of pre-existing "yeast
allergies," 11 reports described probable or possible
anaphylaxis after HBV. Four additional cases were described after other
vaccines. The majority of vaccinees who met the case definitions and had a history of yeast
allergies were female, ages ranged from 10 to 64, and symptom onset ranged from 15 min to 5 h after vaccination. No deaths were reported. The small number of reports to VAERS may be partly due to health care professionals observing current
contraindications by not vaccinating yeast sensitive individuals. Nevertheless, yeast associated
anaphylaxis after HBV in sensitized patients appears to be a rare event.