LIVE POLIO IRUS VACCINES

384
Effieacy-Laboratory Evidence
384 Efficacy-Laboratory Evidence
At this point, the remaining negative children
in the group that were being followed serologically,
were fed another dose of trivalent vaccine
and they then exhibited a further marked immunogenic
effect. The total conversion rate after
the two doses of vaccine was 96 per cent for
Types 1 and 2, and 72 per cent for Type 3-
despite the interfering effects resulting from the
massive infection with other enteric viruses
(which was still 55 per cent in January 1960),
and the simultaneous administration of all three
types of poliovirus. The lower final conversion
rate for Type 3 may also be related to the fact
that we did not use the pH test for low-avidity
antibody, which occurs more commonly after
infection with the Type 3 virus. It should also be
noted that the second feeding was not a mass
feeding but involved only 44 children under four
years of age, who were distributed among a
large number of families throughout the city.
The results might have been even better if nature
had been given another chance at dissemination
of the polioviruses in the community by feeding
all the children under four years of age another
dose of the vaccine.
Fig. 5 shows that with these two feedings of vaccine
it was possible to achieve an immunogenic
effect within a few months and without any cost in
paralysis, comparable to that achieved by nature
only after four years and at a price of about 56
cases of paralytic poliomyelitis.
The comparable serologic effectiveness of the
same lots and doses of vaccine used in trivalent
or monovalent form under different conditions in
children in northern climates is shown in Table
7. It is evident that when the interval between
the separate, sequential feedings of the three
types was not less than four weeks, the antibody
conversion rates were 100 per cent or close to it,
while the mixture of all three types yielded conversion
rates of only 82, 80, and 71 per cent,
respectively, for the three types in a mixed
group of single-negative, double-negative, and
triple-negative children, living under conditions
TABLE 7. EFFECTIVENESS OF ALIQUOTS OF SAME LOTS AND SAME DOSES OF VACCINE USED IN TOLUCA,
MEXICO WHEN GIVEN TO CHILDREN OF COMPARABLE AGE DURING WINTER AND SPRING MONTHS IN
NORTHERN CLIMATES
Trivalent Versus Monovalent (1-3-2)
INVESTIGATOR
PER CENT DEVELOPED
PLACE METHOD No. OF CHILDREN ANTIBODY FOR
AGE OF CHILDREN OF WITHOUT ANTIBODY INDICATED TYPE
TIME OF YEAR ADMINISTRATION FOR INDICATED TYPE 1 2 3
Smorodintsev Trivalent 29 neg. for 1 82
Leningrad, USSR
Children's Homes Tested 4 months 54 neg. for 2 80
Up to 7 years
later
May, 1958 All together in 38 neg. for 3 71
camp during
summer
Smorodintsev
Leningrad, USSR
Children's Homes
Up to 3 years
Feb., March, Apr. 1958
Monovalent
4 week interval
Tested one month
after each type
147 neg. for 1
68 neg. for 2
67 neg. for 3
97
100
96
Verlinde Monovalent 20 neg. for 1 100
Leiden, Holland
Individual Families 3 week interval 18 neg. for 2 90
Up to 14 years
May or Dec. 1957 28 neg. for 3 100