LIVE POLIO IRUS VACCINES

Response of Newborn Infants to Vaccination with Living Type 1 Poliovirus 303
ministered, one month afterwards, and thereafter,
as circumstances dictate.
Feces. In the case of newborns, three fecal
specimens are collected from each infant during
their stay in the hospital, which is on the average
of four days. After their discharge home two
specimens are obtained per week for a minimum
of six weeks. In selected instances, fecal specimens
are also collected from other members of
the family. In addition to the specimens from the
infant, a specimen is obtained from the mother at
the time of delivery and other infants in the
nurseries are sampled once a week.
Specimens are secured from the older infants
twice weekly for six weeks after feeding.
VIRUS ISOLATION
Virus isolations are performed in monolayer
cultures of monkey-kidney cells by methods that
have been in use in this laboratory for a number
of years.
THE STUDY POPULATION
Newborns. Mothers are interviewed in the prenatal
clinics at the Cleveland Metropolitan General
Hospital and at University Hospitals of
Cleveland. The program is explained to them and
if they agree to participate, they are asked to
sign a permit for their baby to be fed the
vaccine. The infant is fed virus within the first
24 hours of life. In some instances, this is done
before he has received any nourishment; in
others, shortly following a meal. The majority
of the babies are Negroes and the families come
from the lower socio-economic stratum of society.
Three-Month-Old Infants. The three-monthold
infants have been recruited from two sources.
One group has consisted of those attending the
Well Baby Clinics conducted by the Department
of Health of the City of Cleveland. They come
from the same population group as the newborns.
The other group consists of occupants of a
Catholic home for children. Most of them are
awaiting adoption. A higher proportion of these
children are white and the details of their backgrounds
are not available to us.
All of the infants accepted into the study, except
for those in the institution, are followed by
the staff conducting the study who assume responsibility
for supervision of their well baby care.
RESULTS
Viral excretion. To date, 150 newborn infants
and 58 infants three months of age have been
vaccinated. The data are still much too fragmentary
to permit any extensive presentation of
results. It is apparent, however, that approximately
80 per cent to 85 per cent of the newborn
infants excrete virus in the feces for a significant
period of time. A small number is found to
have virus in the feces only during the first few
days after feeding. It is doubtful that this represents
true infection of the bowel and more likely
is the result of simple transit of the fed virus
through the gastrointestinal tract. Unfortunately,
no quantitative estimations of the amount
of virus in the feces are available as yet. In
contrast to the newborns, all of the 26 infants
three months of age on whom there are adequate
observations have excreted virus for one week or
more.
The length of time that the infants have continued
to excrete virus is summarized in Table 1.
It will be seen that approximately 70 per cent of
the newborn infants tested in the first week after
feeding was positive. Only about 50 per cent is
found to have virus in their feces during the second
week, and there is a steady decrease in the
numbers excreting virus during the subsequent
weeks. However, a few are still positive in the
seventh week. In examining the individual protocols,
it is striking that many of the newborn
infants have negative specimens interspersed
with positive ones. The feces may be free of
virus for a week or more, after which time virus
reappears. It is possible that this represents
reinfection from family contacts that were themselves
infected from the vaccinated infant. Our
data do not provide an answer to this question.
No such irregularities in isolation of virus from
the consecutive specimens from three-month-old
infants was noted.
It is interesting to compare the results during
the second week in the older infants with those
in the newborns. Although the numbers are
small, 100 per cent of the 15 older infants were
excreting virus as compared to only 55 per cent
of the newborns. This would suggest further that
the gastrointestinal tract of the older infant is