LIVE POLIO IRUS VACCINES

460
460
Discussion
Discussion~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
feeding of oral vaccine to 100,000 persons One can draw a family of curves with incidence
(50,000 with placebo and 50,000 with vaccine) of paralysis as ordinate and age as abscissa. In
and, on the very careful surveillance that Dr. each curve the highest level of incidence is at
Eklund, here present, has been carrying on the adolescent-young adult age level 15-30.
there. 1 think those data should be made available
With progressively decreasing virulence the
for comparison.
curves become lower and at a certain level the
only paralysis to be expected will be a small
CHAIRMAN RHoDES: 1 shall comply with your
suggestion, Dr. Anderson; but first, Sir Macfarlane
Burnet has asked to be recognized.
proportion in the young-adult age group.
1 suggested at that time that if normally
avirulent viruses were to produce paralysis in a
wholly nonimmunized community, it would be
SIR MACFARLANE BURNET: I believe it is important
to ask the question: If one expected para-
in the young-adult age group. If we have reason
to believe that a population undergoing immunization
with a live vaccine contains a proportion
lytic infection from a very weak virus, in which
groups should one look?
of completely unimmunized individuals, and we
Ten years ago I published a theoretical graph
are looking for possible cases of paralysis, then
in the Bulletin of the Johns Hopkins Hospital,
indicating what experience of paralysis would be
we should look for this among the young adults.
expected in the various age groups of a completely
virgin, unimmunized population with dif-
there is one other place where virus of very low
At this point, I should like to suggest that
ferent strains of virus, at different levels of virulence might produce paralysis, that is, in
virulence. Based upon experience in virgin soil infants and very young children. It is in this
epidemics the graph looked like this:
group that one would expect to find immuno-
HYPOTHETICAL INCIDENCE IN VIRGIN-SOIL POPUILATIONS
L)
u
u
-J
ca
o
z
o
e-
o
o
0 10 20 30 Yrs.
A G E