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this borough in the past has been based on the soundest lines, and compares most favourably
with so-called modern improvements, even if the procedure was a trifle more tedious in the past.
In addition it must be remembered that many of our old cases recorded as reversions were only
faintly Schick-positive and undoubtedly possessed a potential immunity which would have been
fully restored by the first contact with diphtheria infection. This is a phenomenon which is
well recognised and accepted when applied to cases in which the original immunisation training
has been a thorough one.
Conclusions.
In considering the results of re-tests in connection with the various antigens and dosages
employed, it must be remembered that the average age of the children attending the clinics has
been steadily declining as the years pass. This is a very desirable feature from the point of
view of conferring immunity at that time of life at which it is most essential, namely infancy
and early childhood.
In the five years preceeding September, 1935, when a comprehensive report on five years'
work at Heston and Isleworth was made, the natural Schick-negative rate of children attending
the clinics was as high as 15.18. This figure has declined fairly steadily year by year until the
prevailing natural Schick-negative rate of all primary cases tested during 1937 proved to be only
9.05%.
Over the same five year period the average age of children attending was 6.24 years as
compared with 4.4 years in one A.P.T. series in 1937 and 3.97 years in the other. It is generally
held that the older the children, the greater the opportunity of natural immunity or partial
immunity having been acquired is present. In other words, within certain limits, moderately
old children are supposed to be easier to immunise than very young children. This is probably
true in areas where the natural immunity rate is high, but in our district, the reverse seems to
emerge from our figures.
The youthful age of the children would appear to militate against a successful result from
the use of our latest antigen, A.P.T. Still it must be remembered that this investigation followed
immediately on the heels of the very highly successful campaign in which A.P.T. as 1.0, 1.5 and
1.5 c.cms. doses was used, and from which such undeniably excellent results were obtained.
On the figures available, the T.A.M. gave nearly a 5% better conversion rate than did the
two injections of A.P.T. in conditions of age and herd immunity practically identical.
It appears, therefore, that the two injections of A.P.T. (Lilly) do not represent any
advance in our immunological procedure, while the single injection, which had been advocated
by the makers, appeared to be at least one fifth less efficient, from our point of view, than those
methods and preparations which we had employed in the past.
It is not denied that A.P.T. is a good and powerful antigen. It is contended that the
optimum method of employing it may not as yet have been determined. At present another
method is being investigated, the giving of two full doses of 0.5 c.c. of A.P.T. at 14 day intervals.
It is possible that this will yield better results. In fairness to A.P.T. it must be admitted that
two injections of T.A.M. will only yield very poor results, and if A.P.T. were employed as a
three injection procedure a very high standard of result could be anticipated with confidence.
At the same time efforts at present are directed to producing a high degree of immunity with
the smallest number of injections, and it is to this end that the increased first dose in the two
injection method is being investigated. It has been stated that better results are obtained from
two injections of A.P.T. when the interval is three weeks or more. We have not adopted this
longer interval because if the time between injections is too long, parents are likely to forget
completely to come again. If they merely have to be told ' Come again not next week, but the
week after,' they seem to remember well. Sometimes the best theoretical considerations must
give way to a slightly less efficient method on the grounds of what is the most practical method as
applied to the parental mind.
GUY BOUSFIELD,
M.D., B.S., Lond.
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