LIVE POLIO IRUS VACCINES

214
Safety-Field Evidence of Safety
she was threatening to abort. She had no significant
antibody titer rise after the feeding. The
other three who aborted had significant antibody
titer rises to one or more immunotypes. The details
of their abortions are not known. One young
woman vaccinated during the 17th week of gestation
had a missed abortion. She had experienced
no antibody titer rise after 2.0 cc. of trivalent oral
vaccine. There is no evidence that the feeding of
the vaccine played any part in her abortion.
Among these 69 women there were three who
produced infahts with congenital abnormalities.
One of these was vaccinated sequentially at threeweek
intervals with monovalent strains of attenuated
virus beginning two weeks before her
last menstrual period. There was no antibody
response to vaccination. The infant was normal
except for a unilateral talipes equinovarus-a
positional defect not related to administration of
the oral vaccine. The other two infants with congenital
abnormalities had more severe defects.
One infant had a bilateral cleft palate, the other
a spina bifida and renal abnormalities. The
mothers of both of these had been vaccinated during
the 16th week of gestation with 2.0 cc. of
trivalent oral vaccine. The abnormalities exhibited
by these infants are developmental and
arise about the fourth to seventh week ovulation
age or the sixth to ninth week of gestation as
measured from the last menstrual period. The
oral vaccine was given too late in pregnancy to
be associated with these defects and therefore
can be dismissed as an etiologic factor.
DISCUSSION AND CONCLUSIONS
Superficial analysis of the first three tables presented
gives the impression that the response of
pregnant women to trivalent oral vaccine is not
very good. An evaluation of these tables shows
that an antibody titer of 1:128 or higher was
present before feeding for more than one-half of
the women studied for each immunotype. This
reflects a heavier natural antibody protection,
more Salk injections or a combination of the
two. A higher frequency of high antibody titers
among pregnant women is to be expected. Probably
no adult group has been more heavily vaccinated
with Salk vaccine than these women selected
by pregnancy. Among any group with antibodv
titers in this high range a poorer overall
response to vaccination as measured by significant
antibody titer rise is to be expected. Measurements
other than total response, therefore,
are necessary to measure the effectiveness of the
vaccine. If the significant responses to oral vaccination
of all women in this group with antibody
titers of 1:64 and below are considered, the per
cent of four-fold antibody titer increases to about
70 per cent for Type 1, about 50 per cent for
Type 2, and about 75 per cent for Type 3.
The real worth of an immunizing agent however,
is measured by its ability to produce significant
antibody titer rises among those who are
antibody negative at the time of vaccination.
When this measurement is made among the pregnant
women in this study a significant antibody
titer response was found to have occurred in
89.7 per cent of all immunotypes. This response
almost is identical to that reported by Cox 5
among 392 antibody negatives who were fed two
cc. of vaccine. Two fifths of the individuals in
this series however, received only 0.5 or 1.0 cc.
of vaccine. This suggests that the larger dose
used by Cox may not be necessary. The results
of this study and those reported by Cox demonstrate
the uniformity of results that can be obtained
with this vaccine among widely separated
groups of people. In this study, better results
as measured by significant antibody titer responses
were not obtained among the immunotype
negatives that had previously received one or
more Salk injections than among those negatives
who had not received Salk vaccine.
Significant antibody responses were occasionally
seen to one, two, or all three immunotypes
as early as 11 days after injection of the trivalent
vaccine. Plotkin O and associates have reported
a significant antibody titer elevation in an infant
14 days after ingestion of CHAT (Type 1) strain.
Re-feeding of pregnant women with trivalent
oral vaccine one or two times at four to six week
intervals does not produce results comparable to
the initial feeding of the vaccine. Analyses of
those with low initial antibody titers show that
those that fail after the first feeding also fail
after the second and third doses when given at
these intervals. These results indicate that an
attempt to revaccinate with trivalent oral vaccine
six or fewer weeks after the first feeding is
not a worthwhile undertaking. One of the au-