Large-Scale Serologic Testing Program to Assess the Immunogenicity of Inactivated Hepatitis A Vaccine (VAQTA™) in Prefilled Syringes Following Product Recall in Germany

Abstract

A voluntary recall of VAQTA™ in prefilled syringes was implemented in Europe in late 2001 after the manufacturer noted a slight decrease in the antigen content of a small percentage of the syringes manufactured over a particular time frame. In Germany, a large-scale serologic testing program was implemented. The assay results were conveyed to the subject’s physician, and free vaccine was provided for anyone requesting revaccination. An analysis was performed on a subset of 58,546 vaccine recipients with hepatitis A antibody results. Of the 28,681 persons who received either two 25 units (25U) or two 50 units (50U) doses of VAQTA™, the seropositivity rate (SPR) was 99.5% after receipt of 2 doses, similar to the results in prelicensure clinical trials. The SPR was similar among recipients of lots that had been manufactured over the time frame associated with the recalled lots versus those receiving lots not associated with the recalled lots (25U: 99.7% versus 99,7%; 50U: 98.6% versus 99.6%, respectively). There were less recipients of 25U doses of the affected lots, who had high hepatitis A antibody titers (≥100 mIU/mL), compared to recipients of unaffected lots.