Vaccination despite thimerosal sensitivity

Thimerosal sensitivity is extremely common in Austria, being surpassed as a contact allergen only by nickel. This high incidence is still rising and is probably due to the frequent vaccinations which are performed in Austria. Most of the patch-test-positive patients had recently been immunized with thimerosal-containing vaccines, and no other obvious sources of exposure to thimerosal could be found. On retrospective questioning, 48 out of 50 patients had had no problems with their recent immunization; the 2 who reported massive local reactions had received their injections, against the recommendation of the manufacturer, subcutaneously. In a prospective study, 12 thimerosal-sensitized persons received their follow-up immunization at our department, and no side effects occurred. This enables us to conclude that sensitization had occurred through vaccines, but that those amounts of thimerosal delivered i.m. are not sufficient to elicit clinical symptoms. Patch-test positivity to thimerosal thus represents no contra-indication to i.m. immunization with thimerosal-containing vaccines.