Towards better pertussis vaccines.

Several recently completed trials have shown that acellular pertussis vaccines induce substantial protection against pertussis. They are considerably less reactogenic than whole-cell vaccines and, as they consist of only one or a few purified proteins, they can be expected to cause less severe adverse events. The optimal composition of acellular vaccines has not yet been determined. The number of vaccine antigens varies from one to five. All vaccines contain detoxified pertussis toxin. Other antigens included in several vaccines are filamentous haemagglutinin, pertactin and fimbriae, but it remains to be proven that these antigens contribute significantly to protection. Postlicensure studies will be of importance in order to study possible rare adverse events after acellular vaccines and to study the induction of herd immunity.