LIVE POLIO IRUS VACCINES

Discussion
325
Discussion 325
ance of Types 1 and 2. This is contrary to what
we had expected because, as you all know, our
Type 2 strain is what you might call the weak
sister of the three types. Here is a case where
Type 3 disappeared and Type 2 reappeared.
Of further interest is the fact that this is the only
child in the family. We know that the mother is
solidly immune to all three types of polio, because
we have re-fed her at six-month intervals
for the past three years. However, we have no
information concerning the serological status of
the father.
At any rate, much to our surprise, the Type 2
strain disappeared and then reappeared and this,
in our opinion, was contrary to all our expectations
in view of what we know about our Type 2
strain.
DR. SABIN: Since the same material was used
by Dr. Gelfand, Dr. Krugman, and Dr. Robbins,
I should like to say that many recent tests have
shown the titer to be 107'3 plaque-forming units
or 107'6 TCD 50 per ml. Therefore, the dose used
by Dr. Robbins was about 106 TCD 50 for threemonth-old
children and 107.6 TCD 50 for the
newborn.
I should now like to comment on the question
of breast feeding raised by Dr. Lépine. 1 have
also been concerned about that because, as Dr.
Lépine may recall, a number of years ago I carried
out extensive studies on feeding human milk,
which had been titrated and shown to contain
antibodies for polio, to monkeys, which were then
fed virulent poliovirus by mouth. The human
milk was given, not only before the virus, but
its feeding was continued for, 1 believe, seven or
14 days thereafter, several times a day; that had
no effect upon the incidence of infection of paralytic
polio in the monkeys.
I also have fed mixtures of gamma globulin
and virulent virus, in which the antibody was in
excess, and found that there was some dissociation
in the intestinal tract of the monkeys, because
some of them developed antibody.
For a time I thought that this showed that
antibody-containing human milk had no effect on
infection of the alimentary tract by poliovirus,
until I realized that the pathogenesis after feeding
in monkeys and chimpanzees is different from
what it is in human beings. In monkeys and
chimpanzees most of the infection occurs in the
posterior pharyngeal wall, while in human beings
the lower intestinal tract is also very susceptible.
So if monkeys swallow human milk and then
are given large doses of the virus by mouth, they
could have their posterior pharyngeal wall infected,
and the milk in the stomach or in the intestinal
tract would have very little effect.
Therefore, I do think that at the present time
we should look into the question of what effect
antibody-containing human milk can have even
when taken in much larger quantities than I
could ever administer to monkeys-because a
child of a few weeks of age will take about a
quart of milk or so. For this reason, I think it
would be worthwhile if Dr. Krugman and Dr.
Robbins might, as far as possible, obtain a history
of breast feeding, both during the first few
days and later, on those mothers who have been
involved in this study. Because in many of the
economically underdeveloped areas, subtropical,
and tropical regions, certainly in the Far East,
breast feeding goes on for a long time. I think
that we should get more information on this.
There is one other point. Amazement has been
expressed about the appearance and disappearance
of individual types of virus in persons to
whom a trivalent mixture of polioviruses was fed.
I think if one will refer to the Proceedings of
the First Conference held here last year, one will
see a number of studies on individuals to whom I
fed trivalent or bivalent mixtures. These were
young adults in a federal reformatory without
contact with the outside, and there the same
phenomenon was evident.
Now, whether the virus can remain for two or
three weeks in the intestinal tract without being
detected in the stools I do not know, but there
is no question that when multiple types are fed
at the same time this is a phenomenon that has
been repeatedly observed and confirmed.
It is of importance because I think that this
limited multiplication of any one type in the
intestinal tract after trivalent mixtures are fed,
even when all three types may appear, is reflected
in a poor resistance of the intestinal tract to
reinfection, months and years later.
DR. GOLDBLUM: I should like to ask both Dr.
Plotkin and Dr. Krugman concerning the newborns
and infants who were found to excrete
virus and failed to produce antibodies.