Serosurvey for polio antibodies.

From 1982 to 1988 a serological survey was performed on 573 subjects aged 3-80 years in order to evaluate the polio immunity level of the population. The presence of neutralizing antibodies was tested using the types 1, 2 and 3 Sabin vaccine strains as well as a wild strain of poliovirus type 1 isolated in France in 1978. According to their birth date, the subjects were assigned to 4 groups. The differences between the groups consisted in the different vaccination history of the subjects as well as in their different opportunities of having been in contact with the past epidemics of poliomyelitis. The results obtained indicate a satisfactory polio immunity level in all the 4 groups: seropositives, 96.7%-98.9% for type 2, 91.8%-98.2% for type 1 (Sabin vaccine strain), 89.3%-96.6% for type 3 and 84.2%-96.4% for type 1 wild strain. The highest immunity levels were found in group D (children with recorded history of complete polio vaccination) and in group A (unvaccinated people but contemporary with the past polio epidemics). A special comment is made with respect to 14 subjects showing satisfactory antibody titres for all the three types of Sabin-vaccine strains but who have proved to be seronegative (less than 4) for the wild type 1 poliovirus strain.