Clinical relevance of lower Hib response in DTPa-based combination vaccines

Combination vaccines are essential to enable administration of all the requ ired antigens in routine infant immunisation schedules at any single visit. Some combinations of diphtheria-tetanus-acellular pertussis (DTPa) with Ha emophilus influenzae type b (Hib) conjugate vaccines have been shown to res ult in lower Hib titres than when Hib is administered separately. While con firming that a primary series with a DTPa-HBV-IPV/Hib combination gives low er antibody levels than separate Hib conjugates, we show that the nature (i sotype and IgG subclasses) and function (avidity and opsonic activity) of t he antibodies are the same, and immunologic memory is induced. It is likely therefore that the DTPa-HBV-IPV/Hib combination will be efficacious agains t Hib disease. (C) 2001 Elsevier Science Ltd. All rights reserved.