LIVE POLIO IRUS VACCINES

326
Discussion
326 Discussion
Would they kindly give us the details on the
degree and duration of virus excretion. I am
bringing this up since this is in disagreement
with what we have found in older infants. In
our experience, there was excellent correlation
between virus excretion and antibody response.
DR. PLOTKIN: In answer to that point, let me
say that we have included only infants in whom
excretion was established beyond a period of several
days after feeding. As for the data regarding
duration of excretion, we have not noticed a
difference in the duration of excretion of the newborn
infants and the infants fed later in life.
However, our data are somewhat influenced by
the fact that most of the infants are fed the other
virus types sequentially, so that there is an artificial
cutoff of excretion.
It may be that if we allowed excretion to go on
indefinitely, excretion beyond the period of three
or four weeks after the feeding would occur in
one group and not in the other, but insofar as I
can answer your question, Dr. Goldblum, we
have no reason to believe that the newborns excrete
less than do the older infants.
DR. PERKINS: There is striking similarity between
the problems that people are facing in
obtaining antibody response after feeding of live
virus vaccines and those that we had when
attempting to immunize infants and the newborns
with Salk vaccine. Both maternal antibody
interference and the lower response of the newborn
infants are presenting problems.
Latterly, we attempted to overcome the interfering
effect of the maternal antibody in the newborn
by giving not two but three doses of vaccine,
each at four-week intervals, as a primary immunizing
stimulus. While it appeared at first
that the response was no better than there had
been to two doses of vaccine, all these infants
have now been recalled at 12 months of age, given
a booster dose (this was the fourth dose of vaccine),
and bled 10 to 14 days later. We now
see that we have some excellent booster responses
in these infants, so that it is quite clear that all
those infants were sensitized in their primary immunization
course to Type 2 and Type 3, and
more than 90 per cent of them to Type 1.
The lessons that we have learned from this
could also be applied to the live virus problem
and these are twofold: the first is that the increase
in antigenic stimulus has had a marked
effect upon these infants, resulting in our being
able to overcome maternal antibody interference;
and the second is that one should delay one's
assessment of the immunity state after the first
feeding, until a booster or refeed is given, for it
is at this time that one is better able to assess
what has happened in the original feeding
experiments.
DR. GEAR: The question of serologic tolerance
has been raised, and to complete the picture, I
wonder if one of our speakers could tell us the
antibody response of infants whose mothers were
fed virus before the infants were born.
We have seen a number of cases of poliomyelitis
in mothers and in their newborn infants
at the same time, nearly all of whom died. We
have also seen several cases of mothers who
contracted poliomyelitis during pregnancy and
who subsequently gave birth to normal babies.
Two such babies have been followed up for one
year. The purpose was to find out whether
they would respond to formalinized vaccine by
producing antibodies to the type causing the
mothers' infection.
We found that the babies had antibodies
against Type 1 virus at birth, at six months, and
again at one year. Presumably, the later period
antibodies resulted from active infection, possibly
occurring before birth.
The question is whether there is any evidence
of in utero infection in the vaccine-fed mothers,
and if so, are their babies immunologically
tolerant?
DaR. PLOTKIN: Dr. Gear, I cannot tell you
whether in utero infection has occurred. We have
vaccinated infants of several women who were
given live virus vaccine during pregnancy, and
we did not detect a difference in their response.
They apparently were still susceptible to infection
and capable of producing antibodies.
Whether an in utero infection might have occurred
we cannot say.
I should like to take this opportunity to make
several points concerning the evaluation of the
effect of transplacental antibody. I think that
some attention should be given to the means of
administration of the virus, for the reason that