LIVE POLIO IRUS VACCINES

Vaccination of Pregnant Women and Young Infants With Trivalent Vaccine 215
thors ' has unpublished data showing that refeedings
of trivalent oral vaccine at a six to 12
month interval to adults other than pregnant
women produce a better over-all immunologic
response.
The definite association of rubella, when contracted
by the pregnant woman during the first
trimester of gestation, with the production of developmental
effects in the fetus has sensitized
obstetricians to all viral diseases occurring during
pregnancy. Recently it has been shown 10 that
certain attenuated viruses injected into pregnant
animals produce teratogenic effects in the fetuses
without any observable sign of illness in the
mother. Although no association between wild
poliomyelitis virus and congenital abnormalities
has been made, several authors have reported a
possible increase in abortion rate in even mild
cases of poliomyelitis." ' 12, 13
Although data has been collected from the infants
of 69 women vaccinated before the twentieth
week of gestation we are especially interested in
those 26 who were fed live attenuated poliomyelitis
vaccine during the first 13 weeks of their
pregnancy. Of these, 20 showed a significant
antibody titer rise to one or more immunotypes.
No congenital abnormalities attributable to the
feeding of the trivalent oral vaccine were seen.
Of the four abortions in this group vaccinated
during the first trimester one was definitely not
related to the administration of the vaccine and
can be removed from consideration. Of the 25
patients that remain three aborted and could
conceivably be related to the administration of
the vaccine. Since the expected rate of abortion
is 10 to 12 per cent for all pregnancies, these
three represent an incidence that is no higher
than that which would be expected to occur by
chance alone.
SUMMARY
Trivalent oral live attenuated poliomyelitis
vaccine in three different dosages were given to
310 pregnant women in all trimesters of pregnancy.
The immunologic response among these women
was comparable to that achieved by others in
non-pregnant individuals.
No statistically significant differences could be
detected between the results achieved with the
three different dosages used.
Although the number of observations is small
no increase in abortions above that expected by
chance alone was observed among those women
vaccinated during the first trimester of pregnancy.
No teratogenic effects attributable to the administration
of the vaccine were seen.
Part 2.
Immunization of Young Infants Under Six Months with Live
Attenuated Oral Poliomyelitis Vaccine
METHODS AND MATERIALS
Participants. Infants of six months of age or
younger who were born at University of Minnesota
Hospitals participated in the study. Some of the
parents and siblings of these infants had participated
in earlier studies of oral and Salk poliomyelitis
vaccine conducted by the authors. Both
clinic and private patients are included in the
group.
For this study the infants were divided into two
groups. One group composed of newborns was
vaccinated at a median age of five days. The
other group composed of infants two and one-half
to six months old was vaccinated at a median age
of four months.
Some of the infants in both groups were lost
to the study when parents objected to blood
drawing or moved from the area. About 90 infants
in the newborn group and 47 in the older
group returned one or more times to allow the
taking of blood for post-vaccination antibody
titer determinations. With a few exceptions a
cord blood was obtained at the time of delivery
from each infant studied to determine the level
of passively transferred maternal antibody titer
at birth.
No newborn infant included in any of the results
tabulated in this report received Salk vaccine
prior to the determination of the result of
the oral vaccine feeding. Two infants in the
group fed at age four months received a single
injection of Salk vaccine between birth and the
time of vaccination with oral vaccine. Neither
of these infants had a measurable antibody titer
to immunotypes 1 or 3 at the time of feeding.