Polio immunization: benefits and risks.

There are epidemiological as well as legal risks to polio immunization. The physician should compare the risks of vaccination with the risks which attend nonvaccination. Another view of the incidence of paralysis following oral poliovaccine (OPV) shows that the risk is about 1.6 cases per 10(6) nonimmune children given OPV and that this rises to about ten cases per 10(6) nonimmune adults exposed to OPV. There is little evidence of reversion to virulence of the virus and it is proposed that susceptibility of vaccinees and contacts to OPV is genetic. The risk of contracting poliomyelitis from either vaccine or wild virus rises about tenfold from the age of about three years to about ten years and thereafter remains constant. The risk of vaccinating children must be balanced against a tenfold risk of vaccinating when older and against a very much higher risk of paralysis or death from a wild virus. Present vaccination policies have virtually eliminated wild virus from the United States but have left many nonimmunes. The consequences of reintroduction of wild virus are examined, and the legal implications of genetic susceptibility are briefly discussed.