Seroepidemiology of polioviruses among university students in northern Italy

The widespread use of poliovirus vaccination schemes has led to a marked decline in the incidence of paralytic poliomyelitis worldwide, but wild poliovirus is still endemic in some developing countries, and in 2009 a total of 23 countries reported at least 1 case of poliomyelitis caused by wild-strain polio viruses. A serological survey was thus conducted on the immunological status against polioviruses of 318 young adults, classified by their country of origin. Immunity to poliomyelitis was assessed by neutralizing antibody titration in tissues cultured on microplates. The rate of seronegativity (≤ 1:8) in the study population was 26.7% for poliovirus type 1, 7.2% for type 2, and 22.6% for type 3. In our sample of 318 individuals, 219 (68.9%) were Italian and 99 (31.1%) were from outside the European Union (EU). The proportion of cases found seropositive to polioviruses 1 and 3 decreased significantly with older age; this age-related decrease was more evident in the Italian group than among the non-EU subjects. Any risk of the wild virus recurring and causing paralytic poliomyelitis must be prevented, keeping Europe polio free by means of appropriate immunological protection, until polio has been conclusively eradicated all over the world. Judging from our findings, it may be worth considering administering a fifth dose of polio vaccine to adolescents.