Clinical and immunological investigation of a new combined hepatitis A and hepatitis B vaccine.

As with hepatitis B vaccines, the recently developed hepatitis A vaccine is suitable not only for individual protection, but also for public health control measures. For introduction into routine immunisation programmes, however, hepatitis A vaccine should preferably be combined with other already established vaccines. In particular, a combination of hepatitis A and hepatitis B vaccines would be appropriate. We investigated a new combined hepatitis A/hepatitis B vaccine comparing its tolerability and immunogenicity with that obtained after separate or mixed simultaneous administration of the two components. Three groups of healthy volunteers, each of approximately 50 persons, were included. All were negative for hepatitis A and hepatitis B markers and had normal liver enzyme values. They received hepatitis A (720 ELISA units) and hepatitis B (20 micrograms) vaccines in the deltoid muscle, combined, mixed or separately, according to a 0, 1, 6-month schedule. Blood samples for determination of antibodies to hepatitis A virus (anti-HAV) and hepatitis B virus (anti-HBs) and of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were drawn at months 0, 1, 2, 6, and 7. Local and systemic reactions were monitored by means of questionnaires. The results of our study demonstrate that the combined hepatitis A and B vaccine is well tolerated and highly immunogenic. The seropositivity and seroprotection rates were 100% for both antigens in all groups. Surprisingly, anti-HAV and anti-HBs antibody titres after the combined and mixed vaccines were significantly higher compared with the respective monovalent vaccines injected separately.