Changes in serotype distribution may hamper efficacy of pneumococcal conjugate vaccines in children

During the last 10 y we have observed an increased incidence of pneumococca l bacteremia in Sweden. In order to study the serotype distribution over ti me we collected 1136 invasive pneumococcal isolates from 1987, 1992 and 199 7 from Swedish microbiological laboratories. Currently, new pneumococcal co njugate vaccines are being considered for introduction in the general child hood vaccination program in several countries, including Sweden. We studied the potential vaccine coverage rate for the new conjugate vaccines among o ur Swedish invasive isolates. We found that the serotype distribution fluct uated with time and observed a surprisingly low potential coverage rate for the 7-alent vaccine in Sweden, in contrast to other countries. Therefore w e argue that pneumococcal conjugate vaccines have to be tailored to suit cu rrent, local serotype patterns and most likely will need to be changed over time.