SAFETY AND IMMUNOGENICITY OF A COMBINED DIPHTHERIA-TETANUS-ACELLULAR PERTUSSIS-INACTIVATED POLIO VACCINE-HAEMOPHILUS INFLUENZAE TYPE-B VACCINE ADMINISTERED AT 2-4-6-13 OR 3-5-12 MONTHS OF AGE

Methods. In an open randomized study we compared the safety and immuno genicity of two schedules for priming and booster vaccinations of infa nts. A pentavalent combination vaccine, including a lyophilized Haemop hilus influenzae type b-tetanus toroid conjugate vaccine reconstituted with a liquid diphtheria, tetanus, acellular pertussis (pertussis tor oid and filamentous hemagglutinin) and inactivated polio vaccine (DTaP -IPV/Act-HIB (R); Pasteur Merieux Connaught, Lyon, France) was adminis tered to 236 Swedish infants either at 2, 4 and 6 months or at 3 and 5 months, and a booster dose was administered 7 months after the last p rimary dose. Adverse events were monitored by diaries for 3 days after each vaccination and by questions at the ensuing visits. Antibodies a gainst the different vaccine components were analyzed after the primar y series of vaccinations, before and after the booster injections. Res ults. There were no serious adverse reactions, and the rates of febril e events and local reactions were low in both groups. The three dose p rimary schedule induced higher geometric mean concentrations for all a ntigens than did the two dose schedule, but there were no differences between the groups in proportions with protective antibody titers agai nst diphtheria, tetanus, Hib and polio or in proportions with certain defined levels of pertussis antibodies. Prebooster results showed a si milar pattern, with the exception that the group primed with three inj ections showed higher proportions of infants with detectable antibodie s against poliovirus types 1 and 3. After booster vaccinations there w ere no differences between the two schedules in geometric mean or in p roportions with antibodies above defined antibody concentrations, indi cating effective priming from both primary series of vaccinations. Con clusion. The combined vaccine DTaP-IPV/ Act-HIB (R) vaccine was equall y safe and immunogenic when administered according to both time schedu les studied.