Serotype replacement in perspective

An increase in the incidence of invasive pneumococcal disease (IPD) caused by non-vaccine serotypes (NVTs) (serotype replacement) has been observed since the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7), primarily in the elderly, HIV-positive adults, and children with underlying medical conditions. In children aged <5 years, only a slight increase in replacement disease due to NVTs has been observed, but the relationship of changes in serotype carriage to replacement disease is not well understood. Predominant post-PCV7 NVTs include serotypes 15, 19A, and 33F, but the increasing antibiotic resistance of 19A is of particular concern in both vaccinated and unvaccinated populations. (C) 2009 Elsevier Ltd. All rights reserved.