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Medical Research Council Trials.
In August, 1956, a report on the relation between protection
in children and results of laboratory tests was published in the
medical press.
The report was prepared by the medical officers of the Medical
Research Council who were in charge of the organisation of the
whooping cough trials. This report was addressed to the Whooping
Cough Immunisation Committee of the Medical Research Council
and to the Medical Officers of Health of the ten Local Authorities
concerned, of which Walthamstow was one.
The Walthamstow trials took place between 1948 and 1951
and children were allocated to a vaccine group in succession as their
names were received. After the injections had been completed,
arrangements were made for each child to be visited monthly for
about 24 months. Special visits were paid when it was known
that a child was being exposed to pertussis or had symptoms which
might be those of the early stages of the disease. Swabs were taken
from vaccinated children with coughs and also so far as possible
from infective cases to which vaccinated children were exposed.
The doctors and nurse-investigators visiting children during the
follow-up period did not know which vaccine a child had received.
Vaccines tested in Walthamstow were V.l, V.2, V.3, and 979
children completed a course of three injections. Children 6-18
months old were given three doses of vaccine intramuscularly with
an interval of one month between injections. The first two doses
were each 0.5 ml., the third 1 ml., and the total dose, in terms of
the U.S.A. opacity standard, was approximately 70,000 million
organisms. Consent forms were received from the parents of 11,093
children in all areas ; 9,794 (88%) of the children completed the
course of three injections.
The report concludes with the following summary:—
In two series of field trials, 14 pertussis vaccines were tested
for their protective potency in 28,799 children. The vaccines used
in the first series of trials were poor, but those in the second series
gave substantial protection, which was maintained for at least two
and a half to three years after vaccination.
At the same time as the field trials were in progress, laboratory
tests were made in which the vaccines were tested for their ability
to protect mice against intracerebral pertussis infection. Some of
the vaccines were also tested for their ability to produce specific
agglutinin in mice and children.
A comparison between the field and laboratory results showed
good correlation between the potency of vaccines in protecting children
and their ability to protect mice against intracerebral infection.
There was also evidence of a correlation between protection in