LIVE POLIO IRUS VACCINES

Vaccination of Pregnant Women and Young Infants with Trivalent Vaccine
225
Time of Vaccinotion
- Age 5 doys
%c
-l Age 4 months
s r
'so
6%
Type 1 Type 2 Type 3
four months infant ready for immunological response
to ingested attenuated polioviruses.
Because there is considerable variation ' in the
age at which an infant reaches his full immunologic
capacity, prompt responses to antigenic
stimuli at any age after delivery are possible.
The number of prompt responses to oral vaccine
shown in this study for each immunotype confirms
this.
The more frequent and higher per cent of
successful responses to Type 3 is a reflection of
antigenic potency. The immunologic responses
among adults and children to the trivalent oral
vaccine used in this study have proved consistently
that this strain is more antigenic than
either the Type 1 or 2. The lower cord titers for
Type 3 when compared to Types 1 and 2 in the
infants in this series may enhance the response
to this type virus.
Stool excretion data from this study showed
the Type 3 virus to have been present in the
stool of 14 of the 15 infants fed. In contrast
Type 1 virus was found in only 10 of 15 infants.
Those infants that failed to excrete Type 1 usually
had high homotypic antibody titer. The only infant
that failed to excrete a Type 3 virus had an
antibody titer of 1:1024. Type 3 virus was excreted
from two infants with titers of greater
than 1:1024. These results show that the Type
3 virus has a greater ability to establish itself in
the intestinal tract than the Type 1. The Type 2
virus was not recovered from the stools of any
of the 15 infants studied who were below the age
of six months.
From the data presented, it can be concluded
that neither vaccination at age five days nor at
four months will give the infant protection to all
three types of poliomyelitis viruses as measured
by antibody titer response. The response to
Type 2 is poor for each group. The responses to
Type 1 and Type 3 are about 10 per cent better
for the group vaccinated at age four months when
compared to the per cent of successful delayed
responses at six months for the group vaccinated
at birth.
It is obvious from these data that the infants
in both groups need revaccination. At age six
months, the group vaccinated at age five days will
respond to repeat feeding. This has been
demonstrated. At age six months, however, only
two months or less after previous feeding, this
group vaccinated at age four months may be refractory
to revaccination.
It is logical to conclude that two vaccinations
with trivalent oral poliomyelitis vaccine at the
suggested interval will give better over-all results
than one vaccination at age four months. For
this reason I favor routine vaccination at discharge
from the newborn nursery followed by a
repeat feeding at age six months. What per cent
of failures in the over-all group will be salvaged
by the second feeding is not known at this time.
The answer, however, will be known in the near
future.
The immunologic responses in both groups of
children and the simultaneous isolation of Types
1 and 3 from the stools of 10 of 15 children fed,
indicates that no serious degree of interference is