LIVE POLIO IRUS VACCINES

Discussion
373
-~~~~~~ics o 7
dominantly in those individuals who have no
measurable antibody titer before feeding.
DR. MELNICK: I should like to ask the people
who have discovered viremia in their vaccinees
whether they have done any studies on the virus
recovered from the blood, to see whether or not
it differs in any way from the virus originally
present in the vaccine.
DR. SABIN: I have previously reported that in
studies on three strains, viremia was detected in
only two persons with the Type 2, P-712, Ch,2ab
strain. In those two, the virus that was isolated
from the blood was tested intracerebrally in
monkeys using very large doses; as regards
neurovirulence, at least, there was no difference
in the properties.
DR. MURRAY: I wish to add one comment to
what Dr. Paul said earlier. This concerns our
evaluation of antibody rises in individuals who
already have antibody.
In the end, I think the definitive analysis of
the serological effectiveness of these vaccines
must depend upon the results with triple negatives,
or at least homotypic negatives. The dynamics-and
even the phenomena themselvesof
the rises in those who already have antibody
are different, and it is very difficult to equate
these.
I have just one additional comment on this
question of four-fold antibody rises. Presumably,
this is selected to eliminate experimental variation
in individual tests. 1 think that by doing so,
if we can neglect the falloff of the antibody during
the interval the vaccine was being administered,
we may actually be introducing some
bias in an upward direction unless we correct it
for the number of antibody falls as well.
We have noticed that in tables which have
been presented here there are a number of falloffs
which are 1/8. I saw a few of 1/16 and
even 1/32. This bias may not be important in
demonstrating a trend but certainly it may be
of some importance when we come to calculate
exact percentages.
DR. BODIAN: I think this point is important
enough so that it should perhaps be stated in
several ways. It seems to me that the possibility
of heterotypic responses in all of those individuals
who were discussed in relation to conversion
this morning has to be taken into account,
and certainly the low rate of conversion in triple
negatives leads to the suspicion that many of the
conversions which were included were transient
heterotypic responses. So I think that Dr. Cox
ought to clarify the assumption about the rate
of conversion when serum is taken at one month,
when in fact his results in triple negatives suggest
that some of those conversions were
fictitious.
DR. LANGMUIR: I should like to refer briefly
to Dr. Cox's paper in connection with the data
he presented on the proportion of sero-negatives
to type in relation to Salk vaccination for his
rather unusual population, namely, a large group
of adults, some 600 I believe, and a small group
of children, about 98, I believe, of Lederle
employees.
The laboratory tests shown are the result of
two phenomena: immunization with Salk vaccine
and natural immunity. I do not believe this is a
valid table until it is broken down by age groups.
Also, he raised the point of the 13 per cent
Type 1 seronegatives, and pointed out how close
this was to the proportion of vaccine failures
that we have reported in the United States this
year. Again, this must be carefully related to
age. I do not think any blanket over-all comparison
is valid.
DR. HORSTMANN: While Dr. Cox is answering
the questions, I wonder if he would tell us exactly
what he means by a "booster" effect? Does he
imply true infection in this case and, if so, how
does he rule out heterotypic antibody responses?
DR. Cox: In the tables I showed this morning,
we did not carry out excretion studies. Accordingly,
our data represent purely a serological
study.
It is true that we do not have the data on
the above children to present to you, although
we are in the process of carrying out studies
along these lines.
I do have available conversion square charts,
if anyone wishes to see them, showing how the
booster responses were calculated on the basis
of serological results.