Immunity status to polioviruses among non-European Union immigrants in Veneto Region (North-East Italy)

Widespread use of poliovirus vaccines has lead to a dramatic decline on the incidence of paralytic poliomyelitis in the Western Hemisphere. In Italy, the use of live attenuated vaccine (OPV) has lead to virtual eradication of poliomyelitis. However, wild poliovirus is still endemic in some less developed countries, and there is still a risk of importation of wild-virus poliomyelitis as result of immigration from these areas. Therefore, a serologic study of the immunologic status to poliovirus was carried out in 242 immigrants from less developed countries in the Veneto Region (North-East Italy). The overall prevalence of serum neutralizing antibodies was 98.3 percent for poliovirus type 1, 99.6 percent for type 2, and 95.9 percent for type 3. The modal titres were 1:128 (21.1 percent), 1:512 (26.4 percent), and 1:32 (22.3 percent) for poliovirus type 1, type 2, and type 3, respectively. No subject was simultaneously lacking neutralizing antibodies to all three polioviruses. The mean duration of stay in Italy before testing was 1.53 years (range 1 month to 7 years). These results show a good level of the immunity status, similar to those found in the Veneto general population. Although the risk of paralytic poliomyelitis in our population is very low, seronegative immigrants originating from areas of high endemicity could reintroduce wild poliovirus. It is therefore important to maintain a careful surveillance system on the importation of wild poliovirus and to plan vaccination programs for unprotected immigrants.