Polio immunity in Ontario

With reference to the article by King, 1 the population in Ontario cannot be considered to be fully immune to poliomyelitis when one considers the immune status of people 60 years of age and older. In all probability these individuals were never vaccinated against poliomyelitis during their infancy, childhood or adolescence. The vaccines were not available before 1960.

Such people could become infected with paralytic poliomyelitis if they were exposed to wild, live or vaccine-derived strains in the event of any importation and dissemination of the virus in Ontario or during a trip abroad. Indeed, two healthy British men, aged 62 and 65 years, were infected with paralytic polio while holidaying in Morocco. 2