LIVE POLIO IRUS VACCINES

Discussion
461
logical anomalies of the agamma-globulinemia
type, or others not yet recognized. In children
with poor defenses, either congenital or due to
slow maturation of the defense mechanism, I
believe you might again expect to find an occasional
case of paralysis from virus which in a
normal population is completely harmless.
I should also point out that if this high susceptibility
of the young adult is a fact, then in
any country with wide and early dissemination
of wild polioviruses among children, there would
be no adults left unimmunized by the natural
process and their potential susceptibility would
never become manifest.
In other words, in Central America, or other
countries where natural immunization is at the
very early age, you would certainly never see
such adult cases. But if cases are going to occur
with very low virulent virus in relatively nonimmune
communities, this is the age group to
be watched.
DR. FLIPSE: Sir MacFarlane, I should appreciate
your comment as to the probable risk or
chance of seeing similar phenomenon in cortisonized
individuals, patients whose reticuloendothelial
system has been damaged by X-ray
and by drugs, such as those used to treat leukemia
and Hodgkins disease, and also in patients
with recent oropharyngeal surgery, because these
groups have been challenged in significant numbers
in our trial. I think your experience and
judgment would be appreciated by this group.
SIR MACFARLANE BURNET: The only comment
I could make would be in regard to the evidence
that children being treated with cortico-steroid
drugs have shown alarming reactions to chickenpox,
including some deaths. I should feel, again,
that a nonimmune child under cortico-steroid
therapy would be another possible candidate for
abnormal susceptibility.
I am speaking only of the potential areas in
which it would seem worthwhile to look for
cases with a vaccine which we know from experience
to be perfectly harmless to normal
individuals.
CHAIRMAN RHODES: As for the question addressed
to the Minnesota group, would Dr. Barr
care to answer it?
DR. BARR: Minnesota planned a mass trial
study in which 103,000 people were fed between
24 March and 20 May 1960. The studies were
conducted in Minneapolis, St. Paul, Duluth, two
suburbs of Minneapolis (Bloomington and St.
Louis Park), and three rural counties located
in the central part of the State.
The number of participants ranged from
31,000 in Minneapolis, 21,000 in Duluth, 17,000
in St. Paul, to 16,000 in Bloomington and St.
Louis Park, and a like number in the three rural
counties. They covered the entire gamut of
people, from poor socio-economic groups in the
three cities and the rural areas to the silkstocking
group in the metropolitan areas.
Feedings were tied in with the local school
systems, with participation on a voluntary basis.
As we have described before, the field trials were
all done as double-blind studies in which the participants
went to the school and did not know
whether they received oral vaccine or placebo.
Out of 103,000 fed, one half of the participants
received placebos and one half received the Cox
strains of the attenuated oral polio vaccine.
Interestingly enough, the vaccine we fed in
Minnesota was from the same batch as that
which was used in Miami. In fact, on 24 March
(the day we started), we received information
about the reported cases of polio in Miami.
I called the health officer in Miami and asked
for specific information, as we were starting
our feeding studies in Minneapolis that night.
On reviewing the information he gave us on the
five cases, and consulting with the oral vaccine
advisory committee to the State Board of Health
(headed by Dr. Gaylord W. Anderson), we went
ahead with the study.
I must admit that when we received this report
at the very last minute we had some qualms.
1 might also add that Minnesota had five cases
of Type 1 polio during the first three months of
1960. The last reported case occurred on 4
March; it was a non-paralytic case from which
we isolated Type I virus.
To my knowledge, this case, which had first
symptoms 20 days prior to the beginning of the
study, is the last one that has occurred in the
State of Minnesota to date.
All persons who participated did so on a volunteer
basis. The communities of Bloomington and
St. Louis Park asked to be included in the study;