Since 1996 in Germany primary infant immunization against Haemophilus influenzae has been most commonly given in the form of diphtheria-tetanus toxoids-acellular pertussis/ H. influenzae type b (DTaP/Hib) or diphtheria-tetanus toxoids-acellular pertussis (-inactivated poliovirus)/ H. influenzae type b (DTaP-IPV/Hib) combination vaccines. These combination vaccines elicit lower anti-Hib antibody concentrations than the equivalent Hib conjugate administered as a separate injection, but the clinical relevance of this phenomenon is unknown.
Methods and findings.
To assess the impact of DTaP/Hib combination vaccines on the incidence of invasive Hib disease in Germany, two independent surveillance systems, one hospital- and one laboratory-based, were used during 1998 and 1999 for detection of cases. Vaccination histories of all cases detected were obtained by telephone contact with parents or health care providers. During the 2-year study period invasive H. influenzae disease in the <5-year age group continued to fall, with a mean annual incidence of 1.01/100 000 children. National vaccination coverage rates revealed that only 70% of children given DTaP/Hib or DTaP-IPV/Hib received the recommended three doses in their first year of life, but the overall effectiveness of these vaccines was high at 97.5% (95% confidence interval, 96.3 to 98.4) for those who had received at least one dose. In subjects who received the full 3-dose schedule, effectiveness was 98.8% (95% confidence interval, 98.2 to 99.3).
Although it is well-documented that DTaP/Hib vaccines elicit lower anti-Hib titers than separate vaccines, such combinations are effective in reducing the incidence of invasive H. influenzae type b disease.
From the Pediatric Infectious Diseases Service, Department of Pediatrics at the Center for Preventive Pediatrics, Johannes Gutenberg University, Mainz (HJS), the Department of General Pediatrics, Christian-Albrechts-University, Kiel (BH), Institut für Soziale Paediatrie und Jugendmedizin, Ludwig-Maximilians-Universität, Munich (RVK, MH), and Robert Koch-Institut, Berlin (AS, WN), Germany; and GlaxoSmithKline Biologicals, Rixensart, Belgium (RC, JW).
Accepted for publication March 27, 2001.
Address for reprints: Prof. H-J. Schmitt, Pediatric Infectious Diseases Service, Center for Preventive Pediatrics at the Johannes Gutenberg University, Langenbeckstrasse 1, 55101 Mainz, Germany. Fax 49 61 31 17 47 50 33; E-mail Schmittj@kinder.klinik.uni-mainz.de.