| seroprevalence of antibodies to poliovirus in individuals living in portugal, 2002. | the last case of poliomyelitis in portugal caused by indigenous wild poliovirus occurred in 1986 and the country was declared polio-free in 2002. high levels of immunity must be maintained to prevent the importation of wild poliovirus. in this study, we determined the immunity against poliomyelitis of the portuguese population in order to identify possible immunity gaps. a representative sample of 1,133 individuals older than two years residing in mainland portugal was studied. logistical diffic ... | 2007 | 17991403 |