Potency of field samples of oral poliovirus vaccine.

The transport and storage facilities and the potency of oral poliovirus vaccines currently administered in 108 centres in India were investigated. Storage and distribution practices in many of the centres were far from ideal. There was no significant loss of potency in the vaccine samples collected from a few centres, while samples from other centres showed a 60-99% loss of virus particles per dose. A national monitoring system has since been established to check the potency of every batch of oral poliovirus vaccine imported and to streamline the transport, storage, and administration of the vaccine. Constant vigilance as regards the quality of vaccines should ensure the success of any poliomyelitis immunization campaign.