["Herd immunity" after administration of Pneumococcal conjugate vaccine and its impact on vaccination campaigns]

Parallel to the diffusion of conjugated pneumococcal vaccine in children, several studies have shown a reduction of the incidence of invasive pneumococcal disease both in the vaccinated and in the unvaccinated. Such an observation is not a surprise if one considers that a similar phenomenon has taken place also after the mass introduction of Hib vaccine, at its turn a conjugated polysaccharide vaccine. Another observation is that also the carriage of vaccinal pneumococci was reduced in both the vaccinated and the unvaccinated, while in some cases the carriage of non-vaccinal serotypes, definitely less pathogenic, could be increased.