Poliomyelitis control in Israel, the West Bank and Gaza Strip: changing strategies with the goal of eradication in an endemic area.

Introduction Since 1949 Israel has faced the difficult challenge of controlling poliomyelitis. We report this experience here, since it could be helpful for identifying appropriate strategies suited to specific countries, especially those in endemic areas, in the current international effort to eradicate poliomyelitis. In the 1940s and 1950s, the patterns of endemic and epidemic poliomyelitis in Israel were similar to those in the USA and Europe. In 1957, the Salk inactivated poliovirus vaccine (IPV) was first used in Israel, resulting in a substantial reduction in the incidence of the disease, although cases continued to be reported. In 1961, during a large epidemic, Sabin attenuated oral poliovirus vaccine (OPV) was introduced in Israel and employed on a large scale, stopping the epidemic in its tracks. OPV was then adopted for general use in the country and has continued to be used in place of IPV since 1961 for basic immunization. In 1967, following the "Six-Day War", Israel became administratively responsible for the Palestinian population of the West Bank and the Gaza Strip. Establishment of large-scale poliomyelitis immunization in these areas using up to four doses of OPV nevertheless failed to prevent substantial poliomyelitis epidemics during the mid-1970s. In 1978, adoption of an OPV/IPV programme led, however, to a remarkable reduction in poliomyelitis cases in Gaza and the West Bank. In 1979, Israel experienced a resurgence of cases, especially among the non-Jewish, primarily Arab population. This led to the institution of an annual immunization campaign using OPV type 1 in addition to the routine infant immunization programme using trivalent OPV. These campaigns helped to reduce the incidence of poliomyelitis to sporadic cases during the 1980s, with no cases being reported after 1985 except for an outbreak in 1988. This outbreak in 1988 occurred in a district of Israel where a trial of the new enhanced IPV (eIPV) as the prime vaccine for infant immunization had been carried out over a period of 6 years. As a result of this outbreak, and the success of the combined OPV/IPV programme used since 1978 in Gaza and the West Bank, Israel also adopted the combined OPV/IPV programme in 1989. Since the 1988 outbreak, there have been no cases of poliomyelitis in Israel, in the West Bank, or Gaza. However, continued vigilance is essential, since wild poliovirus has been found in sewage in Gaza, and there have been substantial outbreaks of poliomyclitis in Oman and neighbouring Jordan as well as chronic endemicity in Egypt. The changing poliomyelitis control strategy in Israel over the past four-to-five decades has been the result of lessons learned from the complex experience of attempting to eradicate the disease in a part of the world highly endemic to wild poliovirus. Historical survey Transition from endemic to epidemic poliomyelitis in Israel, 1948-56 Like other countries in the period 1940-48, this area suffered from outbreaks of poliomyelitis and was considered to be endemic, there being approximately 30 cases of paralytic poliomyelitis per annum with an annual incidence of 5 per 100 000 population. Beginning in 1949, there was a sharp transition from endemic to epidemic poliomyelitis; in 1949 there were 128 cases; in 1950, 1621 (145 per 100 000); and in 1951, 918 paralytic cases (69 per 100 000) (see Table 1). Table 1: Number of poliomyelitis cases and attack rates, 1940-61, in Israel Attack rate Vaccine(a) No. of cases (per 100 00)(b) 1940-48 -- 30 5.0 1949 -- 128 15.0 1950 -- 1 621 145.0 1951 -- 918 69.0 1952-56 -- 650 40.5 1957 IPV 57 3.0 1958 IPV 573 30. …