Polio vaccine

“The majority of virologists favored the live-vaccine option and regarded killed vaccine as, at best, a stopgap. The most obvious advantage of live over killed vaccine was that it was administered orally, whereas killed vaccine had to be injected, not just once but three times, at intervals, to protect against all three types of poliovirus; mass immunization would be much simpler if the necessity – and fear – of the needle could be removed. Then there was the question of the length of immunity conferred by the killed vaccine, which had yet to be established; if it lasted only one to three years before a booster injection was required, that would create problems for public health authorities. Live vaccine, by contrast, should provide long-term, if not lifelong, immunity, just as the disease did – since the whole point of it was to infect with the disease but in such a mild form as to render it harmless (Gould, 134). “With live vaccine, not only was distribution far simpler . . . but incomplete coverage mattered less, since the vaccine-induced polio would spread of its own accord, and that would be beneficial so long as there was no danger of a reversion to virulence (181).