LIVE POLIO IRUS VACCINES

6. VACCINATION OF FULL-TERM INFANTS WITH
ATTENUATED POLIOVIRUSES*
STANLEY A. PLOTKIN, M.D., JOSEPH S. PAGANO, M.D.,
AND HILARY KOPROWSKI, M.D.t
The Wistar Institute of Anatomy and Biology
Philadelphia, Pennsylvania
DR. PLOTKIN (presenting the paper): For vaccination
with living attenuated polioviruses perhaps
the most important age group is infants less
than six months old. If not vaccinated, these
infants become highly susceptible to poliomyelitis
after they lose the passive protection of
transplacentally acquired antibodies. Furthermore,
from a public health point of view, vaccination
in hospitals shortly after birth would be
maximally effective in reaching groups refractory
to vaccination campaigns.
Previous studies from this laboratory have
shown that it is possible to vaccinate infants successfully
in the presence of maternal antibody,j
even on the day of birth.' However, when performed
at ages under two months, vaccination
was found to be less effective than when done in
older infants. 2 This relative resistance has been
further explored s and is the chief subject of the
present communication.
The subjects of these studies were infants living
in the nursery of an institution, under close
supervision. Because of their young age, contacts
between infants included in these trials rarely
occurred. Specimens consisted of stools and
pharyngeal swabs collected twice weekly and
blood specimens obtained at approximately
monthly intervals. Isolation of virus from the
stools and tests for neutralizing antibodies against
poliomyelitis were performed in the manner just
described by Dr. Pagano.
These studies were supported by grants from the
National Institute of Allergy and Infectious Disease.
t Dr. Plotkin and Dr. Pagano (Epidemic Intelligence
Service Officers, Communicable Disease Center,
U.S. Public Health Service, Atlanta, Georgia, on assignment
at The Wistar Institute); and Dr. Koprowski
(Director, The Wistar Institute). The participation
of Drs. Plotkin and Pagano in this study does not
imply endorsement by the Public Health Service; the
opinions are those of the authors.
The viruses used were CHAT (Type 1), 4
P-712 (Type 2),5 and W-Fox (Type 3) ;4 all
feedings were done by allowing the infant to
ingest, by means of a dropper, the virus diluted
in milk.
A successful antibody response, as in the case
of the premature infants, was judged by the
presence of an antibody titer after vaccination,
which was at least four times greater than the
titer which would be predicted from the uninfluenced
normal decline of transplacental antibodies.
The normal rate of decline was determined
from paired serum specimens obtained before
vaccination. The arithmetic and geometric
means determined from these data are given in
Table 1, from which it was computed that the
average half-life of transplacental antibodies is
approximately three weeks. Variability in the
half-life figure was moderate, the standard deviation
being eight days.
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These data may be compared with the half-life
values of 23 days which we have observed in premature
infants; 21 days reported by Perkins and
colleagues in England; 25 days in a paper which
Dr. Gelfand very kindly allowed us to read, to be
published shortly; 21 half-day life of gamma
globulin reported by Dixon et al.; and the 37-day
figure reported by Dr. Martins da Silva and associates.
Age at Vaccination. The success of vaccination
in infants of different ages is summarized in
Tables 2 and 3. Intestinal infection with living
virus was established in more than 90 per cent of
infants fed during the first week of life and also
those fed beyond the age of 70 days. Paradoxically,
between eight and 70 days of age, intestinal
infection occurred at the significantly lower rate
of approximately 70 per cent (Table 3).