LIVE POLIO IRUS VACCINES

Live Poliovirus Immunization-Conditions of Infection with Other Viruses 383
size, climate, hygienic conditions, and geography,
but where no vaccine was given. The incidence
of antibody conversion 10 weeks after the single
dose of trivalent vaccine in single-negative,
double-negative, and triple-negative children is
shown in Table 4. The extent of interference
resulting from the simultaneous administration
of all three types, and the dominance of the
Type 2 strain in this mixture are clearly evident.
Thus, for Type 1, the conversion rate was 100
per cent in the small number of single negatives,
88 per cent in the double negatives, and 55 per
cent in the triple negatives; for Type 3 it was
59 per cent, 42 per cent, and 37 per cent, respectively,
while for Type 2 there was no difference
in the three categories, the conversion rates being
82, 80, and 83 per cent.
An analysis of the data (Table 5) on the children
from whom rectal swabbings were obtained
at weekly intervals, indicated two significant
facts: (1) many of the children who developed
antibody did not excrete sufficient virus to be
detected in the rectal swabs; and (2) some of
the children who had no demonstrable antibody
at 10 weeks excreted enough poliovirus to be detected
in at least one of the rectal swabbings
obtained during the first four weeks. When the
children in the second category are included,
one obtains an estimated total infection rate of
80 per cent for Type 1, 87 per cent for Type 2,
and 47 per cent for Type 3 during the first 10
weeks after the single trivalent dose of vaccine.
Further analysis of these data indicates that
among the total number infected, antibody was
demonstrable at 10 weeks in 86 per cent for
Type 1, 94 per cent for Type 2, and 92 per cent
for Type 3.
The virologic evidence of the marked drop
in the dissemination of polioviruses that occurred
eight to 12 weeks after vaccination is supported
by the serologic data shown in Table 6, which
indicate that among the children who failed to
develop antibody during the first 10 weeks, very
few converted during the subsequent 11 weeks.
100-
90-
, 8 0 '
·> 70-
o 60
. 50
40-
TOLUCA-
VACCINE
_ 20
i0-
o 7M
QUERETARO- NO VACCINE
1007
-' 80-
a,
o 40-
, 30-
FIG. 5. Status of poliovirus antibody in two Mexican cities.