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Vaccines of both types are available to produce active immunisation
against poliomyelitis. When the Government decided to offer facilities
for certain sections of the population to be protected, they deciced on the
Salk vaccine. In the manufacture of this, the three types of virus which
cause poliomyelitis are incorporated. Although it seemed that this vaccine
could bring about an eighty per cent reduction in the incidence of
paralytic poliomyelitis, there had in fact been no definite statistical
evidence of its efficacy. Little was known either about the most efficient
course of treatment, nor how long the effect would last. This meant that
nothing was definitely known about whether further injections would be
required. Nevertheless, this vaccine was decided on, and where it was
used on a large scale it almost certainly contributed to a fall in the incidence
of this infection. It was found that not long after the second of the injections
of the course of two which was first recommended, the level of
antibodies fell. Accordingly, another injection was recommended, the
course now becoming one of three injections. Later, facilities were made
available to the especially susceptible group of children between the ages
of five and eleven to have a fourth injection. The most dangerous of the
three types of virus is type I. Unfortunately, the antibody against this
falls the most readily. It is hoped and can confidently be expected that
vaccine can be manufactured which will result in a high level of antibody
protection against type I and that this can be maintained, even without
repeated booster doses.
In the meantime, vaccines using the living organism were being used.
The best known of these was the Sabin vaccine. This, or a similar preparation,
has been given to some 100 million people throughout the world.
Again, there has been no strict statistical evidence of its efficacy. Its use
on a large scale though does seem to have been followed by a fall in the
number of cases, especially when used while an outbreak was prevalent.
Its use has been followed by antibody production and it has been proved
to be safe. A trial was carried out in this country on babies to determine
the antibody response. In this trial different vaccines were used, and the
doses were given at different intervals of time. The result of this trial
appeared as a report of the Public Health Laboratory Service to the
Poliomyelitis Vaccine Committee of the Medical Reasearch Council in
October. The recommendations of this Committee were that Sabin's
vaccine should be given in three doses of the trivalent mixture at four to
six weekly intervals. The Committee reached the conclusion "that in order
to ensure immunity of the herd as well as of the individual to poliomyelitis,
the Sabin vaccine is preferable to the Salk vaccine. Not only does it
stimulate the protection of antibody equally well, but if affords the
additional safeguard of rendering the gut resistant to the implantation of
the so-called wild polio virus.
The Government has accepted the recommendation of the Joint
Committee on Poliomyelitis Vaccine that the new oral Sabin vaccine may
now be used for the routine vaccination of persons in the priority groups,