LIVE POLIO IRUS VACCINES

Live Poliovirus Immunization-Conditions of Infection with Other Viruses 385
that were conducive to natural spread of the
vaccine strains among them. These results, as
well as other data collected by the Russian
investigators in 1959, indicate that the separate
sequential administration of the three types of
vaccine at intervals of not less than four to six
weeks, is optimum during the cold or cool months
of the year in areas with good sanitation and
hygiene.
CONCLUSION
The results obtained in Toluca, Mexico are
of significance for the vast majority of the world
population, among whom immunity to poliomyelitis
is naturally acquired during the first
few years of life at a varying and sometimes
considerable price in paralysis. In such areas
the feeding of trivalent vaccine on two brief
occasions at an interval of six to eight weeks to
all children under four or five years, depending
on the age incidence of recorded cases of paralytic
poliomyelitis or on the results of a serologic
survey in the region, constitutes a rational, initial
approach at eradication of poliomyelitis. The
rapid disappearance of polioviruses from Toluca
under the conditions of the present study, indicates
that the oncoming generations of children
will have to be similarly vaccinated at the optimum
time during the first six months of life,
because they will have little or no opportunity for
natural acquisition of immunity to poliomyelitis.
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