Experience of combined tetravalent diphtheria, tetanus, whole-cell pertussis and hepatitis B vaccine in Thailand.

In 1992, hepatitis B (HB) vaccination of all newborns was officially included in the national expanded program on immunization (EPI), since satisfactory levels of immunity had been attained among the target populations of Chiang Mai and Chon Buri Province during the trial period, 1989 and 1992. In order to facilitate this process and to reduce the administrative costs created by integration of the additional vaccine, the option of combining HB vaccine with the DTP vaccine was investigated. Thus, in 1991 our group performed a clinical study of Smith Kline Beecham Biological's DTP-HB vaccine, administering it to 160 infants of HBsAg negative mothers at the age of 2, 4 and 6 months, respectively. We found the evoked immune responses to be at least equal to, if not higher, than those achieved with the monovalent vaccine. Likewise, any adverse reactions were comparable to those observed after administering either DTP or HB vaccine separately. According to our additional data, we consider HB vaccination at birth, followed by the combined DTP-HB vaccine at the ages of 2, 4, 6 and 18 months, respectively, most advantageous and we would recommend integrating this regimen into the basic immunization service. Thus, the possibility of eradicating hepatitis B infection altogether might eventually be provided.