LIVE POLIO IRUS VACCINES

DISCUSSION
CHAIRMAN GEAR: Thank you, Dr. Kitaoka.
The last four papers presented, including the
last two of the third session, are now open for
discussion. Dr. Dick.
Dr. DICK: I should like to ask Dr. Gard and
Dr. Kimball a question.
First, would Dr. Gard please give us more
details of the monkey non-neurovirulent virus isolated
from the paralytic patient? I should like to
know whether the virus was recovered from cord,
or from the stool of the patient.
Second, I should like to ask Dr. Kimball if she
has obtained any titrations to support her statement
that Salk vaccination does not affect virus
excretion. "Salk vaccination" I take to mean the
use of a potent vaccine given in three injections
properly spaced.
DR. KIMBALL: These children had vaccine over
a long period of time. We have no measure at all
of the potency of the Salk vaccine used. We had
numerous children in this study of Salk vaccination,
who had no antibodies so I cannot speak at
all for the potency of the vaccine. We only take
the record of the vaccine that the children have
had; then, if they do have antibodies, we feel that
we cannot determine whether the antibodies are
natural or Salk-induced.
The Salk vaccine was, in general, reasonably
recent because this study was done in 1958 and
the children were all quite young.
DR. GARD: With reference to the non-neurovirulent
strains isolated from paralytic cases, my
first personal experience was with virus isolated
as early as 1935. It was a case described by Dr.
Carl Kling, the first study published on the inapparent
infection in monkeys. The material
under study was lymph nodes. It was greatly disputed
at the time, although I think his critics
have come around later and have admitted that
inapparent infections in monkeys may occur.
Be that as it may, later, on at least two occasion,
we have had isolations of virus from one
202
lethal case and one paralytic case, and isolations
from stool, where virus identified as poliovirus in
neutralization tests did grow in tissue culture but
failed to bring down one monkey inoculated with
each strain of virus.
DR. BELL: I should like to comment on Dr.
Gard's observation on the spread of polio infection
from children less than two years of age, as
contrasted with the spread from older children.
With respiratory spread diseases, namely, pertussis,
rubeola, and varicella, we find that the spread
in families tends to be toward the same age
groups. For example, if a school-age child
brings it into the household, then the exposed susceptible
school-age children are most likely
infected, whereas the child in the crib and other
very young children are the least likely to be
infected. Dr. Gard's data indicate a different
pattern of spread for polio infection.
I wonder if Dr. Gard has made allowances for
the age of the contacts who are exposed to the
infected child?
DR. GARD: I should not say that we have made
any observations of such large numbers that we
should like to generalize. I shall merely mention
one case where our index child was a boy 11
months old, who happened to be a twin. The
two twin brothers spent the whole day together in
a playpen. There were two older boys in the
family, one aged three and the other five. During
the observation period, which lasted about 12
weeks-that was the time the index child continued
to excrete virus-we could never isolate
any virus from the twin brother, but we did
isolate virus from the two older children. It was
first isolated from the three-year-old brother who
had developed a special affection for that particular
twin,-the index child-and who used to pick
him up out of the pen and hug him. One week
later, virus was isolated from the five-year-old
brother.
On other occasions, however, we have observed,
in connection with index children of about two,