Poliomyelitis immunity status at different intervals from vaccination.

Research on neutralizing antibodies against the 3 serotypes of poliovirus was carried out on 441 blood specimens drawn from children and young people living in Parma, a town of about 200,000 inhabitants, where the vaccination services were well organized. From June 1983 to June 1984 blood samples were taken from different groups of subjects at different stages of vaccination (before vaccination, and after 1, 2, 3, and 4 doses of trivalent balanced OPV). In addition, groups of children and young people vaccinated from 2 to more than 14 years earlier were bled. Ten per cent of unvaccinated babies (aged 1-3 months) were lacking in neutralizing antibodies for types 1 and 3 and five per cent for type 2; among children aged 4-5 months vaccinated by one dose of OPV a residual 5% of subjects without antibodies for type 1 was also found. All subjects who received two, three, or four doses, had antibodies against all serotypes of poliovirus. As for the number of administered doses, significant differences among GMTs of antibodies were recorded only for type 1, when the group given 3 doses, was compared with the group which received two and one dose, respectively. At different intervals from completion of vaccination (2-14 years), all groups we examined still had antibodies against all three serotypes. For poliovirus type 1 antibody, GMTs were not significantly different in the examined groups. For types 2 and 3 significant decreases were observed in the groups vaccinated from 2 to 5 years. The high levels of immunity observed earlier in Parma were not found throughout the entire territory.(ABSTRACT TRUNCATED AT 250 WORDS)