Israel in the elimination phase of poliomyelitis--achievements and remaining problems

Following the introduction of a combined EIPV and OPV schedule in 1990, no more cases of paralytic poliomyelitis were diagnosed and no wild poliovirus strain was isolated in the sewage. 100% seropositivity and high geometric mean titers (GMTs) to the three types of poliovirus vaccine strains and to the type 1 poliovirus 1988 epidemic strain were observed at the completion of the immunization schedule and one year later. The study of the immune profile of various age groups vaccinated with either EIPV or OPV had shown that the immunity to the epidemic poliovirus strain was less satisfactory, in terms of percent of seropositivity and GMTs, than to the poliovirus vaccine strains. In individuals previously immunized with either EIPV or OPV a high and quick immune response to both the 1988 epidemic and vaccine strains was observed after a booster dose of OPV. Follow-up to four years after the booster pointed to some decrease in the extent and intensity of the seropositivity to the 1988 epidemic strain as compared to the immune profile to the poliovirus vaccine strains. Maintaining Israel in the phase of polio elimination requires: > 95% national coverage, homogenously distributed; maintaining high immune profile to the three poliovirus types, including a satisfactory immune level to the 1988 epidemic strain in all the age groups at risk of polio; early detection of the introduction of wild poliovirus into the environment and of the occurrence of foci of indigenous activity; reducing the risk of exposure to massive infectious doses.(ABSTRACT TRUNCATED AT 250 WORDS)