Immunogenicity, efficacy, safety and effectiveness of pneumococcal conjugate vaccines (1998-2006)

In this paper we present an overview of the literature on efficacy and safety trials of the various pneumococcal conjugate vaccines on the market (PCV7) and in development (PCV9, PCV11 and allegedly PCV10 and PCV13), as well as of observations from post-licensure studies. Seven- (PCV7) and nine-valent PCV (PCV9) are reported to be sufficiently immunogenic after administration of a 3+1 schedule in infants in various RCTs. PncOMPC (PCV7 with a protein of N. meningitidis as a carrier) is less immunogenic, though this may have no repercussions for the protective efficacy against clinical disease. PCV7 is 82-97% efficacious against vaccine serotype (VT) IPD, 90% efficacious against (clinically diagnosed) pneumococcal pneumonia, and, like the 11-valent PCV, 57% efficacious against VT acute otitis media. Naturally, it would be of paramount public health interest if the same levels of efficacy and effectiveness could be achieved with fewer doses. Trials studying 2+1 vaccination schedules for PCV7 and PCV9 generally show that the percentage of infants achieving the protective cut-off set by the World Health Organization (WHO) 1 month after the last priming dose, is comparable to that found at the same time point in studies administering 3+1 schedules. PCVs are generally very well tolerated and safe, also when co-administered with other childhood vaccines. As more and more countries are using these vaccines routinely, post marketing surveillance studies will further establish the safety profile of PCVs.