Safety and immunogenicity of a combined diphtheria-tetanus-acellular pertussis-hepatitis B vaccine administered according to two different primary vaccination schedules

Abstract

The reactogenicity and immunogenicity of a tetravalent diphtheria-tetanus-acellular pertussis-hepatitis B (DTPa-HB) vaccine (SmithKline Beecham) were studied in 565 infants immunized according to one of two different schedules, at 2, 4 and 6 months of age (group A n = 208) or at 3, 5 and 11 months of age (group B n = 357). The incidences of local and general reactions within the first 8 days after vaccination were similar in the two groups of infants, the vast majority being mild in intensity and occurring within 2–3 days of vaccine administration. Severe local symptoms were rare: pain after 0.6% of all doses, redness after 0.5% and 1.3%, and swelling after 0.3% and 1.5%, in group A and B, respectively. Only one infant in group A and one in group B had a temperature > 39.0°C. Both schedules proved satisfactory in obtaining high levels of antibodies against all antigens. The rates of serologic response against the different antigens reached 100% in both groups. Antibody titres against all vaccine components were elevated following both schedules, but after the third dose of vaccine geometric mean antibody titres (GMTs) against D toxoid, filamentous haemagglutinin (FHA), pertactin (PRN) and hepatitis B (HB) were significantly higher in the 3, 5, 11 group than after the 2, 4, 6 schedule. Antibody titres measured at 7 months of age in the group immunized at 2, 4 and 6 months were higher than those reached at 6 months of age in infants immunized at 3, 5 and 11 months, but FHA and PRN were within the range of a DTPa vaccine with proven efficacy. We conclude that DTPa-HB vaccine was safe, well tolerated and highly immunogenic. Both vaccination schedules (2, 4, 6 and 3, 5, 11) can be considered suitable for mass immunization programmes.