Tdap is not associated with excessive reactogenicity in adolescents who received five prior doses of acellular pertussis vaccine

Abstract

Zepp et al provide the first substantial study of safety of administration of a sixth dose of an acellular pertussis antigen-containing vaccine. Since the recommendation in the United States in 1997 for universal use of acelluar pertussis vaccine (aP) instead of whole-cell pertussis vaccine (wP) for all 5 doses in the DTaP series through 6 years of age, reactogenicity (redness, swelling and pain at the injection site; or fever and systemic adverse events; or both within 48 hours of administration) is markedly reduced. As the cohort of children fully immunized solely with aP-containing vaccines has grown, increased reactogenicity after the fourth and fifth doses (still considerably less than after wP-containing vaccines) has been noted. In 2005, two vaccines with tetanus toxoid and reduced-content diphtheria toxoid and acellular pertussis antigens (Tdap) were licensed in the United States and recommended for universal administration in adolescents in order to boost waned immunity. There was a modicum of concern from reactogenicity data following the fifth dose of DTaP in children that a Tdap in adolescents (the sixth dose of an acellular-pertussis containing vaccine) could be associated with heightened reactogenicity. Zepp et al provide reassuring data of only minor reactogenicity following Tdap among study subjects who also had been study subjects for the preceding 5 doses of DTaP. This was true even for subjects who had substantial reactions after the fifth dose. Halperin’s editorial brings into focus the expected safety, benefit, and challenges of using repeated doses of Tdap to curb the rising incidence of pertussis in adolescents and adults, and indirectly to protect very young infants.