Both vaccines were administered as a 0

Both vaccines were administered as a 0.5 mL intramuscular injection into the anterolateral region of the left thigh. DTPw-HBV/Hib vaccine (1 of 3 lots; n = 439; double-blind) or Tritanrix?-HBV/Hib (n = 146; single-blind) co-administered with oral poliovirus vaccine (OPV) at 2, 4 and 6 months, with a booster dose at 18-24 months. Results One month after the end of the 3-dose primary vaccination course, the new DTPw-HBV/Hib vaccine was non-inferior to Tritanrix?-HBV/Hib in terms of seroprotection/vaccine response rates for all component antigens; 97.3% and 93.9% of subjects in the two groups, respectively, had seroprotective levels of antibodies against diphtheria, tetanus, hepatitis B A-366 and Hib and a vaccine response to the pertussis component. Persistence of antibodies against all vaccine antigens was comparable between groups, with marked increases in all antibody concentrations after booster administration in both groups. Both vaccines were generally well-tolerated as primary and booster doses. Conclusions Results confirm the suitability of this new DTPw-HBV/Hib vaccine comprising antigens from a new source and a reduced PRP content for inclusion into routine childhood vaccination programs. Trial registration http://www.clinicaltrials.gov NCT00332566 Background Combined diphtheria-tetanus-whole cell pertussis (DTPw) vaccines remain the cornerstone of childhood vaccination programs in Latin America and many other parts of the world [1]. The addition of new antigens to existing vaccines with established high coverage rates is an efficient method of rapidly achieving high coverage and protection against other important pathogens with minimum impact on vaccination logistics and cost [2-4]. Hepatitis B (HBV) and Haemophilus influenzae type b (Hib) infections remain endemic in many parts of the world, causing disease that can readily be prevented by vaccination [5,6]. Although universal vaccination of infants against HBV and Hib has been recommended by the World Health Organization (WHO) since 1992 and 1996, respectively [7-9], uptake of both vaccines is incomplete. Lack of appropriate combination vaccines and difficulties with vaccine CYFIP1 supply have been identified as key factors contributing to this slow uptake [10]. Tritanrix?-HBV (GlaxoSmithKline [GSK] Biologicals, Rixensart, Belgium), a combined DTPw and hepatitis B vaccine, has been available since the mid-1990s [11]. This vaccine can be mixed with a conjugated Hib vaccine (Hiberix?; GSK Biologicals) and administered as a single injection (Tritanrix?-HBV/Hib) [11,12]. In order to address the A-366 increasing international demand for DTPw-based combination vaccines, GSK Biologicals has recently introduced a new source of DTPw antigens and has developed a new DTPw-HBV/Hib combination vaccine containing a reduced amount of Hib capsular polyribosylribitol phosphate (PRP) (2.5 g per 0.5 mL dose instead of the 10 g PRP contained in Tritanrix?-HBV/Hib). DTPw-based combination vaccines with reduced PRP antigen content have been shown to be non-inferior to those with higher PRP antigen content in terms of immune response to all component antigens after primary and booster vaccination [13-18]. The ability to co-administer DTPw-based combination vaccines with A-366 other routine vaccines would be convenient for both A-366 medical staff and vaccine recipients. Studies have shown the potential for co-administration of combined DTPw-based combination vaccines with other pediatric vaccines, including rotavirus vaccine and oral poliovirus vaccine (OPV) [19]. This study was undertaken to assess the immunogenicity and reactogenicity of GSK Biological’s new DTPw-HBV/Hib vaccine compared with Tritanrix?-HBV/Hib when co-administered with OPV in healthy Latin American infants at 2, 4 and 6 months. Antibody persistence and immune response to a booster dose at 18-24 months of age was also assessed. Methods Study design and subjects This was a randomized, A-366 partially-blind, multicenter study in three countries in Latin America (Argentina, Chile and Nicaragua) between August 2004 and September 2005. The study was approved by the appropriate local ethics committees and conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Healthy male and female infants born after a normal gestation period (between 36-42 weeks) were enrolled for first vaccination at 6-10 weeks of age. In Argentina, mothers of prospective participants were screened prenatally for the presence of hepatitis B virus surface antigen (HBsAg). Infants born to anti-HBsAg seropositive mothers were ineligible for study participation, but were offered HBV vaccination at birth. Other exclusion criteria included: previous diphtheria, tetanus, pertussis, hepatitis B, Hib or polio vaccination or disease; Bacille Calmette-Gurin vaccine given later than the first 2 weeks of life; major congenital defects or serious chronic illness; a.