LIVE POLIO IRUS VACCINES

246
Efficacy-Laboratory Evidence
TABLE 9. FREQUENCY OF VACCINE VIRUS EXCRETION BY CHILDREN DURING THE FIRST MONTH
AFTER IMMUNIZATION BY WEEKS (CHILDREN'S HOMES No. 5 AND No. 10)
WEEK AFTER
IMMUNIZATION
NUMBER OF
CHILDREN TESTED
NUMBER EXCRETING
VIRUS
VIRUS ISOLATION
RATE
1
105
98
93
2
58
53
91
3
102
84
82
4
86
62
72
Maximum excretion of Types 1 and 2 vaccine
viruses was observed in the first post-vaccination
week, and of Type 3 virus in the second week
(Fig. 1). During the first month after vaccination
Types 1, 2, and 3 vaccine viruses are excreted
almost twice as frequently as during the
second month (Table 14). Examples of simultaneous
multiplication of vaccine strains Types
1, 2, and 3 are presented in Figures 2 and 3.
Special investigation was devoted to the problem
of establishment of vaccine viruses in immunized
children in relation to the presence or
absence of poliomyelitis antibody. It was
shown that the establishment of Types 1 and 2
vaccine viruses was almost twice as frequent in
children without antibody than in those with
them. On the contrary, Type 3 vaccine virus
was much more frequently excreted by children
possessing homologous antibody (Tables 15-17).
Examination of sera collected at random from
223 children with pre-vaccination lack of antibody
to some types by pH neutralization test,
showed that one month after feeding with trivalent
live vaccine some children responded with
antibody development to all three types, and
others to two or one type of poliovirus. Of 142
children without pre-vaccination Type 1 antibody,
92 (64.8 per cent) acquired antibody to
this type. Of 106 children without Type 2 antibody
before vaccination, 85 (80.2 per cent) developed
it. Smaller number of children responded
with Type 3 antibody development (86
of 151, or 56.9 per cent). Of 60 triple-negative
children, 27 (45.0 per cent) developed each Type
1 and Type 3 antibody, and 43 (71.7 per cent)
Type 2 antibody.
Percentage of children with pre-vaccination
antibody increased by 39.9 per cent for Type 1,
35.4 per cent for Type 2, and 35.9 per cent for
Type 3.
These results are definitely lower compared to
those obtained by I. H. Dobrova in the Estonian
SSR after immunization with trivalent vaccine
in the winter-spring season (see Table 18).
In the Moscow and Karaganda regions, where
vaccinations had been carried out in the summer,
establishment of vaccine strains was prevented
by extremely wide dissemination of non-poliomyelitis
enteric viruses during this period. In
favor of possible inhibiting influence of enterovirus
season is the fact that the least satisfactory
results were obtained in children's homes L. and
R. where considerable extent of ECHO and
Coxsackie virus carriage had been found (Table
18).
And yet, despite the unfavorable effect of
enteric virus carriage, one feeding of trivalent
live vaccine resulted in significant changes in
antibody patterns compared with pre-vaccination
status in that 128 children of 223 seronegatives
converted to triple positives. Fifty-one of 60
triple-negative children developed antibody to
one or more types of poliomyelitis viruses, and
only nine children remained triple negative
(Table 19 and Fig. 4).
Best results in regard to increase in the percentage
of children with antibody to all the three
types were observed in children from different
towns and settlements of the Moscow region (68.4
per cent) not vaccinated previously with killed
vaccine (Table 20). In the Karaganda region