LIVE POLIO IRUS VACCINES

Discussion
159
Discussion 159
ence in spread related to economic status, and its was not true of the Type 1 and Type 3 strains that
related ecologic concomitants, such as crowding I selected.
and family size.
With Type 1, 1 found that even a dose of 10,000
TCD 50 given to young adults produced infection
DR. GEAR: One brief comment on this question. irregularly and when it occurred it was associated
Similar change in incidence of poliomeylitis in with virus excretion for only about seven to 10
the different economic groups has been noticed days; antibody could be demonstrated at four
recently in communities in South Africa, in the weeks, but not at six or eight weeks.
absence of Salk vaccination.
This finding adds emphasis to the point raised
by Dr. Paul, that is, that you cannot examine antibody
just at one time after infection and have a
complete picture.
We also have evidence that some people can
have infection for three to four weeks with Type
3 virus and when the antibody is determined at
a given point, six or eight weeks later, they have
no demonstrable antibody by methods we now
have available; however, when tested for resistance
of the intestinal tract two years later, demonstrated
a very marked resistance.
Would Dr. Gelfand please answer the question
I posed to him?
DR. SABIN: I should like to comment on the
subject of abortive infections, particularly in the
light of the comments made by Dr. Dick and Dr.
Smadel.
In selecting the arbitrary titer of 32, which was
necessitated by the circumstance of not knowing
the status of natural immunity before Salk vaccine,
we must realize that there were some
naturally immune persons among those with the
low titers, as well as some without naturally acquired
immunity among those with the high
titers; because some children do develop higher
titers than 32 after three or four doses of Salk
vaccine.
Accordingly, some of the abortive infections
could easily be accounted for on the basis of reinfection
of previously naturally immune persons.
Secondly, the failure of antibody response in
some of these abortive infections might be accounted
for on the basis of a high level of preexisting
antibody. In our own studies of reinfection
with Type 3 virus, we found that this particular
type produced reinfection in 50 per cent of
naturally immune adults and it may be higher in
children. We found that if the pre-existing antibody
titers were not very high, then even an abortive
infection of one or two days' duration gave
rise to an increase in antibody. But if the antibody
levels were high to begin with, excretion of
virus for a short period of time did not further
boost the antibody level.
I should like to ask Dr. Gelfand whether there
were any children without any demonstrable antibody
prior to oral vaccination, in whom an abortive
infection occurred, and in whom there was
no antibody response.
1 should also like to comment on the remarks
made by Dr. Dick. He worked with my Type 2
virus strain, and my own titrations with this Type
2 virus showed that it was capable of initiating
infection with very small doses of virus, which
DR. GELFAND: The answer to the first question
is very simple. We did have individuals who had
no antibody demonstrable by our technique, who
experienced abortive infections of one, two, three,
four, or five days, and who had no antibody when
it was tested three months later.
DR. SABIN: By the tube test?
DR. GELFAND: Yes.
DR. SABIN: I interposed this, because as our
published data show, with this Type 3 strain we
have had individuals who have had even longer
periods of multiplication, three to four weeks,
and yet by the tube neutralization test had no
demonstrable antibody and by the pH test showed
titers of 32 and 64.
So this is another thing we must keep in mind
in interpreting Dr. Gelfand's data.
DR. GELFAND: I was reminded also that I had
not answered Dr. Paul's earlier question about
the proper time to do antibody studies following
vaccination. 1 must say that the purpose of our
study was not to acquire information about serologic
response and we made no effort, as we probably
should have, to collect a series of blood