DTPa(+)/Hib combination vaccines: the German experience

ABSTRACT

Background The introduction of polysaccharide-protein conjugate vaccines against Haemophilus influenzae type b (Hib) in the 1990's resulted in a dramatic reduction in the number of cases of invasive Hib disease. In Germany, following the launch of DTPa/Hib combination vaccines in late 1996 and DTPa-IPV/Hib in 1998, the majority of Hib immunisations are made with such combinations. It is well established that such combinations elicit lower anti-Hib antibody concentrations than the equivalent Hib conjugate administered as a separate injection. While there are good reasons to assume that this is of no clinical relevance the clinical impact of this phenomenon has not yet been fully evaluated. Methods and Findings To assess the impact of DTPa/Hib combination vaccines on the incidence of invasive Hib disease in Germany two independent, one hospital- and one laboratory-based, surveillance systems were used during 1998-99 for detection of cases. Tetra- and penta- valent DTPa-Hib vaccines accounted for 92.1 % of all Hib vaccines used in 1999. During the 2 year study period the annual number of invasive Haemophilus influenzae b disease decreased further from 28 in 1998 to 13 in 99. National vaccination coverage rates for 1998/99 revealed that only 70 % of children given DTPa/Hib or DTPa-IPV/Hib received the recommended 3 doses in their first year of life, the overall effectiveness of the most used combination vaccine was high at 97.4 % (95 % CI 96.0-98.3) for those who had received at least one dose of such a vaccine. In subjects who received the full 3-dose schedule effectiveness was 98.8 % (95 % CI 98.1-99.2). Conclusion These data show that the lower anti-Hib antibody concentrations observed with DTPa/Hib combination vaccines are of no clinical relevance (AU)

RESUMEN

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