LIVE POLIO IRUS VACCINES

154
Safety-Field Evidence of Safety
Not too surprisingly, the proportion of unvaccinated
who became infected by contact was directly
related to the proportion of the population
vaccinated. The more extensive spread observed
in the more heavily seeded Franklin community
also testifies to the relative lack of influence on
spread of prior Salk vaccination since the proportion
of children so vaccinated in Franklin
(54 per cent with three or four shots and 79 per
cent with at least one) was much greater than in
Morgan City (15 and 40 per cent, respectively).
Finally, although the abundant occurrence of
wild enteroviruses in the two communities confirmed
our judgment that conditions for enterovirus
spread were very favorable, we were unable
to show that such wild infections interfered with
vaccine virus spread. Rather, the reverse may
have been true since administration of the vaccine
seems to have afforded transient protection
against wild enterovirus infection.
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