LIVE POLIO IRUS VACCINES

Large-Scale Practical Trials, Use of Live Poliovirus Vaccine in USSR 577
Immunization, in 1959. of 15 million persons
in different parts of the USSR; and finally, the
mass immunization campaign against poliomyelitis
in 1960, with the aim of vaccinating
about 75-80 million, that is, practically all of
the population in the country susceptible to
poliomyelitis.
Some figures on the subject are shown in the
text of the paper, and the results of the field
trial in the Baltic republics were mentioned in
the report by Professor Chumakov.
I merely wish to add that the epidemiological
situation in the Baltic republics, established as
favorable in 1959, remained the same during
the first four months of 1960. During this period,
only two cases of polio were recorded in
Esthonia, four cases in Lithuania, and seven
cases in Latvia, as compared with tens and
hundreds of cases in previous years in some
other areas where the population had not been
vaccinated. Dr. Sabin, who is acquainted with
these data, considers that even these isolated
cases may be considered as doubtful because of
hyper diagnosis of the disease.
On the basis of research and field observations
carried out in the USSR, we can summarize our
conclusions as follows:
1. The safety of the live vaccine, prepared
from Dr. Sabin's attenuated strains, has been
proved and it has been shown that no reversion
of vaccine strains took place during the entire
vaccination campaign.
I should like to stress this point particularly
in connection with vaccination carried out in
Moscow and Leningrad, and in other large cities,
where the public health service is fully adequate
and where even isolated cases of the disease
could not be overlooked.
2. It was established that the vaccine had a
high degree of immunological effectiveness, and
during this work optimal schemes of immunization
were elaborated.
3. Virus secretion and its spread among the
contacts appeared to be not only harmless but
even favorable as a complementary useful property
of the vaccine.
4. A convenient method of administration and
use of the live polio vaccine was elaborated as
dragée-candy.
5. It was shown that the vaccination can produce
a satisfactory epidemiological effect in an
inter-epidemic period as well as during an epidemic.
All this permits us not only to hope but also
to be certain that the live polio vaccine is a very
effective means of preventing infection. Moreover,
large-scale use of the live polio vaccine
has put forward as a theoretically possible and
a practicable task the eradication of poliomiyelitis.
This problem-the problem of eradicating
poliomyelitis-needs, however, further thorough
study.
Eradication of a disease which affects only
man and has no reservoirs in nature (and
poliomyelitis is an example of such a disease)
can be achieved in two principal ways: by destroying
the agent or by correcting the reactions
of the host organism.
A classic example of the first way is the
eradication of smallpox. The acute course of
the infection and a highly effective post-infectious
immunity, in the presence of a good vaccine
which closely imitates natural postinfectious
immunity, make theoretically possible and
practically feasible the task of eradicating the
disease; in other words, the complete eradication
of smallpox throughout the world can be
achieved by means of vaccinating the entire population
of the globe.
This task is practically completed in the
majority of the economically developed countries
and now, on the initiative of the WHO, the
problem is being solved in all parts of the
world. I am optimistic and believe that during
the next decade the smallpox virus will be
eliminated throughout the world, remaining only
in laboratories, like certain animals which die
out and remain only in zoos.
An example of the second way is the eradication
of Escherichia coli-dysentery, or, as we call
it in Russia, coli-enteritis. There is little doubt
that enteritis in infants, or at least an important
part of this disease, is the pathological reaction
of a certain portion of infants to the settlement
of coli-bacteria in their intestines, which inevitably
takes place when infants, at the age of
three to six months, begin to be fed food in addition
to their mother's milk. When the children
reach the age of one or one and a half years,
they are ready to bear these normal inhabitants
of their intestines without any sequelae, but
severe illnesses and even deaths may occur in