Results of a program successfully combining live and killed polio vaccines.

Oral polio vaccine (OPV) has been used in the Gaza Strip since 1968. Although vaccine coverage had reached 80 to 90% of the infant population, the epidemiological pattern of the paralytic disease had not changed significantly as of the beginning of this study. The mean annual incidence continued to be around 10/100,000. Two outbreaks occurred, in 1974 and 1976, involving 75 and 77 children, respectively, an incidence of 18/100,000. In these two outbreaks, 34 and 50% of the affected children, respectively, received 3 to 4 doses of OPV. A serological survey done after a vaccination campaign with monovalent Type 1 vaccine showed an unexpectedly low percentage of seropositives. A parallel was found between the prevalence of diarrheal disease and vaccine failure, and a causal effect was postulated. To overcome this problem, a program of immunization was started early in 1978 combining both live and killed polio vaccines. Although cases of polio continue to appear, the incidence has been reduced to 2.4/100,000 population. In 1981, only one case was reported, in an unvaccinated child. Thus, it would seem that the new vaccination schedule combining live and killed vaccines makes eradication of polio a possibility.