LIVE POLIO IRUS VACCINES

Use of Sabin's Live Poliovirus Vaccine in Mexico
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FIc. 1. Polio antibodies in children in 3 Mexican cities before feeding vaccine.
lation of 300,000, had an average of 31 cases of
paralytic poliomyelitis per year.
(3) Approximately 90 per cent of these affected
were children under five years of age.
Although the trial was scheduled for November
and December 1958, for reasons beyond our control,
the administration of the vaccine did not
start until 23 February 1959 in Mexico City, and
27 April in the other three cities. It is important
to emphasize that this delay was very
unfortunate because, based on the experience
of previous years, we were expecting an epidemic
in both Mexico City and the City of Guadalajara.
The epidemic in Mexico City had indeed started
early in January, and in Guadalajara, it was picking
up late in April. By the time the vaccination
program was started, 21 cases each of paralytic
poliomyelitis had occurred in Mexico City and
Guadalajara, three cases in the City of Monterrey,
and one case in the City of Puebla. It was
in this kind of setting that the oral vaccine was
administered.
All the vaccine used in these studies was kindly
supplied by Dr. Sabin, from the large lots prepared
by him in 1956, and fed by different investigators
to several million people.
The strains were administered individually
four to five weeks apart in the following order:
Type 1, 3, and 2 in amount of 0.1 ml., containing
approximately 105.6 to 105 ' 9 TCD 5 o for each type,
in a teaspoon with cherry syrup. Table 1 shows
the total number of children vaccinated and the
period of time during which the different types
of viruses were fed. In Mexico City, only 17.1
per cent of the estimated number of children between
six months and less than five years of age
were vaccinated; in Guadalajara and Puebla,
about 30 per cent; and in the City of Monterrey,
52 per cent. The actual proportion of children
of each age group who received the vaccine in the
different cities is shown in Tables 2, 3, 4, and 5.
Tables 6, 7, and 8 show an estimation of the
actual number of children without Types 1, 2, or
3 polio antibodies who received the different