Feasible improvements in vaccines in the Expanded Programme on Immunization.

Feasible improvements in existing vaccines of the Expanded Programme on Immunization are reviewed. The toxicity of pertussis vaccines can probably be reduced and the immunogenicity increased by recently instituted improvements in purity and selectivity. Candidate vaccines containing inactivated pertussis toxin, with or without other components, are in use in Japan and in controlled trials elsewhere. Inactivated poliovirus vaccines have been improved over the past decade and presently show promise of inducing immunity with as few as two doses administered in infancy. At the same time, improved methods for delivering the oral poliovirus vaccine through mass vaccination campaigns are being increasingly employed throughout the developing world. Major improvements in the measles vaccine will probably come from the development of new stabilizers and the use of vaccines that are immunogenic in the presence of maternal antibody.