LIVE POLIO IRUS VACCINES

Effectiveness of Trivalent Vaccine in Immunizing Young Children
115
An analysis of the results in terms of the overall
patterns of response, the spread of polioviruses
to contacts, and the role of enteroviruses
other than polioviruses will be given by Dr. Paul.
The present discussion will be limited to the
effectiveness of the trivalent vaccine in inducing
infection and immunity in the index children.
A pre-vaccinal virus survey based on tests of two
rectal swabs collected 4-5 days before and on the
day of vaccine ingestion, indicated that 20 of the
48 vaccinees (42 per cent) were already infected
with some agent at the time of vaccination. In
the present analysis, these 20 children are not
considered, and only data on the 28 index children
who were free of possibly interfering viruses
will be given. Of the 28, 19 lacked antibody to
all three types. None of the rest had antibody
to Type 1, 6 were positive for Type 2, 2 for Type
3, and one had both Types 2 and 3 antibody.
The responses of these children to the first and
second doses of vaccine in terms of virus excrefollowed
closely. An exception was excretion of
Type 2: we failed to detect Type 2 virus in three
children who showed antibody conversions for
this type.
.In connection with these results, the family
infection patterns were reviewed carefully. As
will be reported by Dr. Paul, the spread of Type
1 and Type 3 viruses was considerable, but in
no instance was there evidence that the index
child acquired infection from a contact. In no
family did contacts excrete a virus type which
did not infect the index child. Among the total
48 families, there were five in which the index
child was not infected after ingesting the first
dose of vaccine, and in three of these, the second
dose also failed to establish any poliovirus in the
vaccinee. In none of these families was poliovirus
isolated at any time from any of the contacts.
We feel reasonably certain, therefore,
that the results given for the vaccinees, represent
the immunizing effect of the trivalent vac-
TABLE 3. ANTIBODY CONVERSIONS AND VIRUS EXCRETION IN HOMOTYPIC NEGATIVE CHILDREN FREE
OF ENTEROVIRUS INFECTION WHEN VACCINATED
FIRST DOSE SECOND DOSE
TYPE NUMBER PERCENT C PERCENT C
ANTIBODY VIRUS ANTIBODY VIRUS
CONVERSION EXCRETION CONVERSION EXCRETION
I 28 42 62 75 71
TI 21 10 10 35 19
Ir 25 83 84 88 88
tion and antibody rises are given in Table 3.
Antibody conversions one month after the first
dose were observed in 42 per cent for Type 1,
10 per cent for Type 2, and 83 per cent for
Type 3. Virus excretion of Types 1 and 3 was
present in a somewhat higher per cent; subsequent
tests indicated that antibodies had developed
in most of these children by the third bleeding.
By the time one month had elapsed after
the second dose, the conversion rates were 75 per
cent, 37 per cent, and 91 per cent, respectively,
for the three types; the per cent excreting viruses
cine ingested by them, and not infection derived
from some other source.
Responses of children with pre-vaccinal antibody.
Because of the small numbers, all index
children with pre-vaccinal antibodies to any type
are included in this analysis. There were 11
who possessed Type 2 antibody prior to vaccination;
none of these were later demonstrated to
excrete Type 2 virus, but all became infected
with Type 1 and/or Type 3. The Type 2 antibody
responses were, nevertheless, striking: as
indicated in Table 4, 8 of the 11 showed four-