LIVE POLIO IRUS VACCINES

Discussion
575
ence last year. The information now tends to
be in better perspective. We can see more of
what has happened; we tend to be more conservative
in the type of opinions we derived from
these results. I cannot help being impressed
with the figures that were given in the case of
Nicaragua. Even if we calculate the number of
cases in terms of the Type 1 seronegatives, as
was presented in the paper, a rough calculation
comes out at a rate of somewhere near 700 per
100,000, which represents a really tremendous
occurrence of poliomyelitis. One would hesitate
to guess what would have happened if the rest
of the population had not been vaccinated. Even
so, one wonders just why and how the disease
can be propagated at such a tremendous rate.
DR. QUIRCE: (through an interpreter): To
confirm Dr. Paul's statements, I should like to
say that the cases we had in Costa Rica were
86 per cent in children under five years of age.
An interesting point, which is worthwhile
mentioning, is that during the most serious
epidemic we had, in 1954, the attack rate was
118 per 100,000 inhabitants. In the outbreak
we had in the first three months of the year in
the metropolitan area, the attack rate was 128
per 100,000 inhabitants, among the non-vaccinated
groups.
DR. VARGAs-MÉNDEZ: I wish to add something
with regard to this problem of the enteroviruses.
You saw by the chart that there were seronegatives
to polioviruses up to the age of four
years. We have also taken a large number of
rectal swabs during the program. Since we have
no virus laboratory (although we hope to have
one in the near future, with the help of the Pan
American Sanitary Bureau), we have to send the
samples to Cali, Panama, and Pearl River. We
have now received reports from Dr. Shelokov,
Dr. Doany, and from Dr. Cox on findings which
include: Coxsackie B-3, Coxsackie A-4, ECHO-8,
ECHO-7, ECHO-14, ECHO-12, adenovirus, enterovirus
of unknown origin, and so on. We
hope to have more information about this point
in the future. We have to investigate this and
relate it in some way or other to the possibilities
of interference.
DR. LANGMUIR: As I listened to the reports
this afternoon I take some solace in the fact
that our colleagues below the border have been
experiencing some of the same problems as we
have. It seems to me that all of us have been
over-optimistic.
The attack rates in Nicaragua, and even in
Costa Rica, seem to be higher than one would
have anticipated had nothing been done at all.
We have certainly observed that in this country,
in Des Moines, Kansas City, Little Rock, Seattle,
and New Haven. We have an attack rate
in selected unvaccinated residual minority
groups in our population which are excessive,
higher than any recorded before, to my knowledge.
I believe that this is a very serious situation,
the full import of which I am not yet prepared
to judge, although I have gone on record as
believing that this is due to selection out of
viruses of greater virulence than were the average
in prior times.
I believe the lesson, however, is qu'te clear.
Regardless of whether or not we choose to follow
an inactivated vaccine program or a live
virus vaccine program, we shall have to strive,
and somehow, we shall have to reach a much
higher proportion of our population adequately
and fully vaccinated than has been achieved as
yet in most parts of the world.
In Dr. Voroshilova's report presented yesterday,
I was deeply impressed with the amount
of time and attention she took early in her presentation
to emphasize the necessity of giving not
just one triple vaccine once to the population,
but I believe the plan calls for intensive effort
at three months of age, four months of age, six
months of age, the first birthday, the second
birthday, and the third birthday-six doses are
planned. This to me represents the realities of
the situation: to fight the polioviruses will require
a great deal of effort and a degree of
organization which has not yet been achieved.
CHAIRMAN STUART-HARRIS: We shall now
proceed with Dr. Zhdanov's paper on "Large-
Scale Practical Trials and Use of Live Poliovirus
Vaccine in the USSR."