LIVE POLIO IRUS VACCINES

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TOPIC III. EFFICACY. (A) LABORATORY
EVIDENCE (continuation)
5. EXPERIMENTAL INFECTION WITH CHAT ATTENUATED
POLIOVIRUS IN PREMATURE INFANTS*
JOSEPH S. PAGANO, M.D., STANLEY A. PLOTKIN, M.D., DONALD CORNELY, M.D.,
AND HILARY KOPROWSKI, M.D.t
The Wistar Institute and the Philadelphia General Hospital
Philadelphia, Pennsylvania
DR. PAGANO (presenting the paper): Several
investigators have established that infants lese
than six months old can be successfully vaccinated
with living attenuated poliovirus administered
orally. - It has also been observed that
vaccination failures occur with some frequency
in infants less than 60 days old, in contrast to the
usual success of vaccination in infants more than
60 days old.3 Investigation of this age-variation
of the response to attenuated poliovirus was extended
to vaccination of premature infants, in
order to elucidate whether the resistance to vaccination
that was occasionally observed in fullterm
infants was somehow related to biologic
immaturity.3a 5
Opportunities were incidentally afforded to
study experimentally several aspects of virus infection
including: the immunologic response of
premature infants to a viral antigen, the influence
of passively acquired antibodies on vaccination
with attenuated virus, and an estimation of
* This study was supported by a U.S. Public Health
Service grant from the National Institute of Allergy
and Infectious Disease.
t Dr. Pagano (Research Associate, The Wistar Institute);
Dr. Plotkin (Epidemic Intelligence Service
Officer, Communicable Disease Center, U.S. Public
Health Service, Atlanta, Georgia); Dr. Cornely (Director
of Newborn Nurseries, Philadelphia General
Hospital); and Dr. Koprowski (Director, The Wistar
Institute). The participation of Drs. Pagano and
Plotkin in this study does not imply endorsement by
the Public Health Service; the opinions are those
of the authors.
287
the half-life of antibodies of maternal origin in
premature infants.
In addition, the CHAT poliovirus was readministered
orally to some of the infants, in particular
to those that had not responded previously
with the formation of detectable antibodies,
despite obvious intestinal infection with
the virus. The refeeding of these infants was
done to discover whether immunologic tolerance
had been induced, that is, whether in such infants
there would be failure to produce antibodies
after re-exposure to the same antigen later in life.
Subjects, Attenuated Virus Used. Forty-nine
premature infants ranging in weight from 990 to
2100 grams were given 105.7 TCID 50 CHAT
Type 1 poliovirus d by gavage on the third day of
life; 14 infants not given virus were retained as
controls.
Specimens. Specimens of feces collected twice
weekly for the duration of the hospital stay (four
to 10 weeks) were tested for cytopathogenic
effect; viruses isolated from the feces were identified
by serum-neutralization tests. 7
Neutralizing antibody titers were determined
in paired sera from the same infant by a modificationS
of the immune-inactivation test.8 Blood
specimens were obtained from the umbilical cord
t With HeLa-cell tissue culture and 10'
Mahoney virus.
PFU