Immunogenicity and reactogenicity of a combined hepatitis A and B vaccine in young adults

The aim of this study was to assess the immunogenicity and reactogenicity of a combined vaccine against hepatitis A virus (HAV) and hepatitis B virus (HBV) in young healthy adults. A total of 150 subjects (20 +/- 1.4 years; 111 females and 39 males) negative for anti-HAV, anti-HBs, anti-HBc and HBsAg markers, were enrolled and randomized to received the study vaccine from one of the three lots under double blind conditions. Three doses of the combined vaccine were administered by intramuscular route (deltoid) following a 0-, 1- and 6 months schedule. Each dose of 1 ml contained at least 720 ELISA Units of HAV antigen (Strain HM175) and 20 micrograms of recombinant HBsAg. Blood samples for anti-HAV (ELISA), anti-HBs (RIA) and transaminases determinations were obtained 1 month after the administration of each dose and before to the administration of the third dose (month 6). Local and general reactions were recorded by the vaccinee on the day of each vaccination and for the three following days on symptom sheets. A total of 147 subjects completed the study. There were not statistically significant differences between groups regarding to immunogenicity. All subjects had seroconverted [geometric mean titres (GMT): 1311 mIU ml-1] for hepatitis A component following the second dose; GMT increased to 8895 mIU ml-1 after the third dose. Seroconversion rates for hepatitis B component were 98% (GMT, 104 mIU ml-1) after the second dose and 100% after the third dose (GMT, 7097 mIU ml-1). There were not statistically significant differences between groups regarding to incidence of local and general symptoms. Soreness at the injection site and headache were the most commonly local and general symptoms reported, following 42% and 11% of the doses, respectively. This vaccine when given to young adults was well tolerated and induced high immunogenic response, similar to that obtained by hepatitis A and hepatitis B vaccines administered separately in previously reported trials.