LIVE POLIO IRUS VACCINES

Discussion
431
DR. STUART-HARRIS: I should like to ask Dr.
Voroshilova whether she has any evidence concerning
the properties of any strains of poliomyelitis
viruses recovered during 1960, in such
areas as Lithuanian and Esthonia, where mass
campaigns with the attenuated virus vaccination
have been carried out for the longest period of
time.
I recall that when Dr. Sabin was writing about
attenuated virus vaccines some years ago, he
coined the phrase, I believe, of "causing a replacement
of nature's viruses by the attenuated
viruses from the laboratory." One of the interesting
features in his own data, and also in the
data from Czechoslovakia, is the lack of persistence
of the attenuated viruses under field
conditions. I wonder whether we could have
any information on the status in any of the
Baltic States or any other areas of the USSR.
DR. CHUMAKOV (through an interpreter): In
1960, in Esthonia, at the beginning before revaccination,
we carried out some investigations in a
children's home and the results we have obtained
are therefore of limited significance. We do not
want to generalize these data and to apply them
to the whole situation in Esthonia. The data.
however, were interesting.
It so happened that out of 108 samples, about
58 had pathogenic agents, 25 strains being of
Type 3 poliovirus. At any rate, we investigated
eight of them for the T marker. All of them were
T+, but neither in that children's institution,
in the town, nor anywhere in the Republic, did
we register a single case of poliomyelitis at the
time. And since we had a mass circulation of
strains of Type 3 in that children's institution,
this fact led us to carry out the investigation on
a larger scale, of the strains recovered in this
Republic. But this investigation has not been
completed.
We have preliminary data to the effect that this
mass infection with strains of Type 3 poliovirus
was connected with that particular institution
only. So it has not been confirmed anywhere else
and we have not discovered any other strain of
poliovirus.
Furthermore, we had data last year in Esthonia
when we carried out virological investigations on
the various types of diseases-meningitis, for
instance, and various incidents of intestinal diseases-at
that time we discovered several strains
of poliomyelitis virus. Several months after
vaccination, poliomyelitis viruses were still circulating,
if I may put it that way. But last
year we did not have total vaccination. There
were many gaps in that vaccination program,
and we believe that regular vaccination from
the very first days of life, mass immunization
that will reach as high as 90 per cent of the
susceptible population, will make it possible to
exclude the circulation of these viruses more or
less completely. I merely refer to the data which
are now at my disposal.
DR. MELNICK: I should like to ask Dr. Chumakov
if this institution in Esthonia, which he just
mentioned to us, was an institution where vaccination
had taken place the year before, and if
so, whether the children had responded with
antibodies?
The reason I ask the question is because, when
I was in Moscow recently, Dr. Chumakov told me
about a group of children who had been vaccinated
one year before and in whom antibodies
against Type 3 had been produced. But Type 3
wild viruses were found to have infected these
children naturally a year later.
DR. CHUMAKOV (through an interpreter): The
information at my disposal refers to the children's
institution where we had children from
one and a half months to three years of age. It
is obvious that there was a large turnover in
the youngest group. This was not a stable
group; during the year new children were admitted
and others left-those who were over
three years of age. So that before sampling, we
also had unvaccinated children in this children's
home who found themselves in an enviroment
which was favorable to the circulation of various
viruses.
The data obtained were as follows: Out of the
25 strains which belonged to Type 3, we had
eight T+ strains which we succeeded in checking.
Approximately half were found in children
who had been vaccinated during the previous
years and who had antibody.
It is possible that there is no direct correlation
here with the presence of antibodies and virus
of the Type 3. But this has been noted without
the circulation of the virus. It had been men-