LIVE POLIO IRUS VACCINES

Discussion 329
Discussion
329
born of mothers who had a German measles infection
during early pregnancy, that is, children
of evidence, I think, suggests that there is an influence
of maternal antibody, not only on virus
born with congenital defects. The German excretion but on the antibody response. As I
measles infection of these children runs a normal
course.
Many of the protagonists of live virus vaccination
mentioned yesterday, this fits very well in terms
of the critical level of passive antibody that we
have obtained in young chimpanzees.*
would like to know how to discover a poten-
tial tumor-inducing agent in the monkey-kidney
tissue. But this problem should be almost of
equal importance to adherents of inactivated accines.
Since inactivation rate of such a still
imaginary virus is unknown, it could exist in the
formalin-inactivated vaccine and cause tumors
after parenteral injection, a route much more
dangerous for an animal than administration
through the alimentary canal.
Although newborn animals are prone to be
more susceptible to tumor-inducing properties of
such viruses as polyoma or milk tumor agent,
there are many more factors than age involved in
this problem. The genetic make-up, hormonal
imbalance, and influence of neighboring cells are
only a few of the factors to be mentioned. Conversely,
newborn animals are more resistant than
adults to non-tumor viruses such as polio or
lymphocytic choriomeningitis. Where to place
simian viruses in this respect is impossible to
say.
DR. BODIAN: One of the things that have impressed
me at this session is the increase, since
the last Conference, in information about the subject
of immunization of infants. Many questions
which arose last year have at least been approached,
and have partial, if not complete, solutions.
Among the ones that I think deserve considerable
attention are, first, the differences in infectivity
among virus strains fed to newborns and
infants, and the question of whether this may
lead to a solution by means of a single-strain
feeding or, rather, by adjustment of dose.
The studies that we have heard about have included
dosage ranges which vary from less than
5 logs to 7.5 logs. The results in response have
varied to some extent correspondingly.
Second, another area about which we knew
practically nothing last year and know a great
deal about now is the effect of maternal passive
antibody on the excretion of virus in these infants
and on the antibody response. The balance
DR. SABIN: While there are certain similarities
in response of very young infants to dead vaccine
and to feeding of live virus vaccines, there are
also certain differences. When a preformed antigen
is administered, it can combine with antibodies
present in the individual.
I should like to recall some observat'ons made
by my good friend Dr. Cox when we worked together
at the Rockefeller Institute 25 years ago.
He showed that if you added too much antiserum
to formalinized eastern equine encephalitis virus,
it lost much of its effectiveness as an immunizing
antigen.
It is also a fact that younger infants, during
the first weeks of life, produce lower antibody
levels. What has been demonstrated after feeding
live virus vaccine is not that a higher level
of placentally transmitted antibody interferes
with antibody development in infants but, rather,
that when the original levels are high they mask
the demonstration of the lower levels of actively
produced antibody-at least at three months of
age. That was beautifully brought out in the
chart shown by Dr. Krugman.
There is only one other comment I should
like to make with reference to what Dulbecco
said. We know of the so-called "carcinogenic,"
polyoma virus, but in order to demonstrate its
effects, massive doses have to be administered by
injection to newborn mice, while under natural
conditions and after administration by the oral
route, there is no evidence that this virus is
"carcinogenic." If one thinks of the mouse
mammary carcinoma "milk agent," one should
remember that its activity is limited only to certain
breeds of mice.
CHAIRMAN HILLEBOE: We shall now have the
presentation of two papers. The first is by Dr.
Cox on "Recent Experience with the Lederle
Trivalent Oral Poliomyelitis Vaccine"; the second
is by Dr. Kleinman on "Further Experiences
with Oral Poliomyelitis Vaccines in Minnesota."
* Bulletin of the Johns Hopkins Hospital, 1960,
In Press.