Polio outbreaks in Namibia, 1993-1995: lessons learned

In 1993, a nationwide outbreak of 53 cases of paralytic poliomyelitis occurred in Namibia. The World Health Organization-recommended supplemental vaccination strategy of national immunization days (NIDs), providing two doses of oral polio vaccine (OPV) to all children <5 years, was implemented to control the epidemic. A second focal outbreak of 16 confirmed polio cases occurred during 1994-1995 in northeast Namibia. "Mopping-up" vaccination was implemented to control the second outbreak, followed by NIDs. Both epidemics appeared to be associated with wild poliovirus importation from Angola, where polio is endemic. Although supplemental vaccination measures achieved suboptimal OPV coverage, surveillance of acute flaccid paralysis has not detected wild poliovirus in Namibia since April 1995. Future NIDs should aim to ensure OPV coverage >90% in each round of NIDs in each district. Nevertheless, the risk of new poliovirus importations will continue until efforts in Angola to increase routine coverage with three doses of OPV and extend supplemental vaccination activities can be implemented.