Successful control of poliomyelitis by a combined OPV/IPV polio vaccine program in the West Bank and Gaza, 1978-93

In the 1970s the incidence of poliomyelitis in Gaza and the West Bank was high, even among children immunized with as many as four doses of oral polio vaccine (OPV). This was thought to be due to interference in uptake from other enteroviruses in the environment. A combined program of OPV and inactivated polio vaccine (IPV) was instituted in these areas in 1978, and the incidence of polio declined dramatically. Wild poliovirus findings in sewage in 1990-91 coupled with two outbreaks of polio, one in Israel in 1988 and another in Jordan in 1992, were reminders that the area should still be considered endemic. The potential of fresh entry of wild poliovirus may occur via persons who may have personal protection but may still shed the virus due to inadequate enteric immunity. In addition, the combined program protects against vaccine-associated poliomyelitis. A similar modified combined OPV/IPV program has been adopted in Israel. The combination of OPV and IPV provides an important alternative strategy in the worldwide effort to eradicate poliomyelitis.