LIVE POLIO IRUS VACCINES

336
Efficacy-Laboratory Evidence
pre-vaccination antibody titers. This chart is
prepared the same as previous charts. These
figures show those persons that had no detectable
antibody, and here you see the conversion rates.
These are the ratios.
These persons had antibody levels of less than
1:16. These persons had antibody levels of 1:32
but less than 64 and here are shown those with
antibody levels of 128 but less than 256; and
lastly, those who had antibody levels of 512 but
less than 1024, are shown.
FACTORS RELATED TO SEROLOGIC
RESPONSE
The influence of pre-existing antibody levels on
response to oral trivalent poliovirus vaccine is
illustrated in Fig. 4. Here is the, antibody titer
present at the time of feeding; you can see that
the best responses were obtained to Types 1 and
3. One line represents the response to Type 1,
another line represents the response to Type 3,
and still another is the response to Type 2.
Type 3 responses apparently are the best,
which not only have been found by us but by all
of our investigators as well. The curves are
based on the serologic findings in those 1,416
volunteers comprising the three groups whose
pre-vaccination antibody levels were less than
1:1024 and who showed a four-fold or greater
rise in titer after vaccination. The depressing
effect of increasing antibody concentration on the
degree of booster response, illustrated here, is
essentially the same as had been observed previously
when the three viruses were fed separately.
The responses summarized in Fig. 4 are a
composite of approximately 1,300 individuals of
diverse experience with respect to the three types
of poliovirus. The 933 volunteers of group 3 included
61 persons who were without demonstrable
antibody to any type of poliovirus. All
but five of these triple negatives (92 per cent),
responded to both Type 1 and Type 3 virus when
fed the trivalent vaccine. Thus, these triple negatives
responded as frequently to these types as
did all other Type 1 and Type 3 seronegatives in
the entire study group. However, the response
of the triple negatives to Type 2 virus was 60
per cent versus 74 per cent for those who lacked
antibody for Type 2 only. This observation
100%
90
80
70
60
50
40
30
20
10
Antibody Tite 342) \
4/8 16/32 64/128 256/512
Percent with a fourfold or greater
at various prevaccination antibody
levels.
prompted an examination of the data relating to
the responses of those double negatives who were
without antibody to Types 1 and 2 or were negative
to Types 2 and 3. It was found that among
the 45 individuals who were negative for Types
1 and 2, the response rate was 87 per cent for
Type 2, and that among 37 persons who were
Type 2 and Type 3 negative, the response rate
for Type 2 was 84 per cent.
The numbers in these groups are limited but
the data suggest that simultaneous susceptibility
to either one of the other two virus types, but not
to both of them, enhances the response rate to
the Lederle Type 2 strain. These observations
may be indicative of the more subtle antigenic
relationships within the poliovirus group. Gelfand
and his associates 3 have recently reviewed
these intragroup reaction patterns as shown by
the responses to Salk vaccine, and their data, in
addition to showing the inferiority of the Type
1 and 3 antigens in formalin inactivated vaccine,
indicate that the lowest geometric mean
titer attained for Type 2 antigen was found in
children who possessed antibodies for both Types
1 and 3 prior to undergoing a full course of three
Salk vaccine inoculations.
Age did not appear to be an important element
in conditioning the response to the administration
of the trivalent oral poliovirus vaccine, except
possibly in the case of Type 2 virus. The conversion
rates of 95 persons under 18 years of