Pneumococcal vaccines: do they prevent infection and how?

Purpose of review The purpose of this review is to update and summarize information concerning the epidemiology of infections due to Streptococcus pneumoniae and the early results of effectiveness studies of the heptavalent pneumococcal conjugate vaccine. This vaccine was licensed in the US in 2000, and has been used increasingly since that time. Recent findings Several studies have documented a dramatic decline in the rate of invasive infections due to S. pneumoniae in children under 5 years of age. There has been a simultaneous decrease in serious infections in persons over 20 years of age, presumably because of a decrease in transmission of S. pneumoniae to unvaccinated individuals. Three different studies have shown a modest reduction in the overall number of cases of acute otitis media in children who have received the vaccine. Although the overall number of cases has decreased there has been an increase in the number of cases of acute otitis media caused by serotypes of S. pneumoniae not contained in the vaccine. Worldwide, many studies have appeared that examine the prevalence of different pneumococcal serotypes/serogroups as a cause of invasive and respiratory disease, to assess the likelihood that the vaccine will be effective in particular geographic areas. Summary Use of the heptavalent pneumococcal conjugate vaccine has led to a major decline in the prevalence of invasive pneumococcal disease (bacteremia, meningitis) and a more modest decrease in respiratory tract infections (acute otitis media, pneumonia). Continued surveillance is essential to document future trends in the occurrence of pneumococcal infections and the enduring protectiveness of the heptavalent pneumococcal conjugate vaccine.