The golden jubilee of vaccination against poliomyelitis.

Inactivated poliovirus vaccine (IPV), developed in the USA by Jonas Salk in the early 1950s, was field tested in 1954, and found to be safe and effective. The year 2004 marks the golden jubilee of this breakthrough. From 1955 IPV was used extensively in the US and polio incidence declined by more than 95 per cent. However, in 1962, when oral poliovirus vaccine (OPV) became available, the national policy was shifted to its exclusive use, for reasons other than science and economics. The World Health Organisation (WHO) also adopted the policy of the exclusive use of OPV in developing countries. Thus IPV fell into disrepute in much of the world, while Northern European countries continued to use it. New research led to improving its potency, reducing its manufacturing costs and combining it with the diphtheria-tetanus-pertussis (DTP) vaccine to simplify its administration and reduce programmatic costs. All countries that chose to persist with IPV eliminated poliovirus circulation without OPV-induced polio or the risk of live vaccine viruses reverting to wild-like nature. IPV is highly immunogenic, confers mucosal immunity and exerts herd protective effect, all qualities of a good vaccine. It can be used in harmony with the extendend programme on immunization (EPI) schedule of infant immunisation with DTP, thus reducing programmatic costs. During the last ten years IPV has once again regained its popularity and some 25 industrialised countries use it exclusively. The demand is increasing from other countries and the supply has not caught up, leaving market forces to dictate the sale price of IPV. Anticipating such a turn of events India had launched its own IPV manufacturing programme in 1987, but the project was closed in 1992. Today it is not clear if we can complete the job of global polio eradication without IPV, on account of the genetic instability of OPV and the consequent tendency of vaccine viruses to revert to wild-like properties. The option to use IPV is complicated since it is not yet licensed in India, we do not manufacture it and imported vaccine would be prohibitively costly. However, in this golden jubilee year we have much to celebrate as the global eradication of wild polioviruses is within sight. Had we strictly followed the principles of science and health economics, perhaps we could have achieved success earlier and cheaper, with the absence of vaccine-induced polio as the bonus.