Vaccination against poliomyelitis in Poland with types 1 and 3 attenuated viruses of Koprowski: 2. Epidemiological evaluation of results of mass vaccination, 1959-60.

Mass oral vaccination of children against poliomyelitis was carried out in Poland in 1959 and 1960 with type 1 (CHAT strain) and type 3 (W-Fox) attenuated polioviruses. Altogether some 7 239 000 children 6 months through 14 years old received type 1 by May 1960 and nearly 6 818 500 children were fed type 3.Epidemiological observations indicate that the CHAT strain may safely be administered but that the W-Fox strain requires further investigation into the conditions in which it may be used for mass prophylaxis.The incidence of poliomyelitis in Poland decreased very considerably in 1960, the total incidence for that year (0.9 per 100 000) being almost 9 times lower than the median for the years 1951-59. Moreover, the usual summer-autumn epidemic outbreak did not occur in 1960.The efficacy of the vaccine (as calculated from the incidence of paralytic poliomyelitis among the vaccinated and among the unvaccinated) was evaluated at 86%.