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Careful histories have been taken in the case of 515 children who have received injections
of Lilly A.P.T. Of these, 33 cases or 6.4%, showed some degree of undesirable reaction. This
was usually confined to some degree of swelling, redness and pain or tenderness in the arm. A
hard subcutaneous nodule, often quite painless, is frequently noted. No definite case of cold
abscess is on record, though there was a query in one case.
It will be noted that the percentage of reaction is higher than that met with in the course
of T.A.M. injections, where the figure recorded was only 2.2%.
The average of the children who reacted to A.P.T. sufficiently for parents to comment
on the pain, tenderness, redness or swelling of the arm was 6.7 years. This average age is
higher than that of the majority of the children in either A.P.T. group, the figures for the single
and double injection groups being 4.42 years and 3.97 years respectively.
As far as can at present be determined, it appears that the slightly older children are
more likely to develop reactions, even at an average age of only 6.7 years. Also it seems as if
younger children are more easily immunised by means of A.P.T. injections, as the average age
of the children proving to be re-Schick positive is higher than the average age of the groups
immunised.
Natural immunity.
An interesting example of high herd immunity as a result of a few cases of diphtheria
and the presence of a few carriers, was encountered at the end of 1936 and the beginning of 1937.
The seat of the small outbreak was Nazareth House residential girls' School, Isleworth. In
order to check the spread of the disease, a Schick testing and immunising campaign was advocated
by Dr. Nash.
The results of the primary Schick tests proved most illuminating. Of 116 children
tested, no less than 86 cases, or 71.14% were negative. The average age of all the children was
fairly high at 8.87 years. In spite of this the natural immunity was found to be very high, even
among the smallest children. 43 children of 6 years of age and under were tested, and only 15
were Schick-positive, a natural immunity rate of 65.1% even among these very young children.
28 of the 30 Schick-positive children were actively immunised, 25 being treated by means
of two injections of B.W. & Co.'s A.P.T. (0.2 and 0.5 c.c. at 14 day interval). The remaining
three were treated by means of T.A.F. injections, as two of them experienced reaction at the
first injection of 0.2 c.c. of A.P.T. All cases were shown to have been immunised successfully
when re-tests were performed from 3-4 months later.
Three reactions only were reported, in children aged 9, 11 and 15 years of age respectively.
The average age of all the primary Schick-positive children was 7.2 years, and of those
who were naturally immune 9.4 years.
Considerable efforts were made to trace out the process of natural immunisation which had
taken place prior to the investigation. Plans were drawn up at the request of Dr. Nash showing
the position of the beds formerly occupied by diphtheria cases and carriers in the dormatories,
and the relative positions of the children in the classrooms. There appeared to be no detectable
relationship between the naturally immunised children and the apparent situation of diphtheria
infection within the institution. Presumably there was sufficient intermingling of the children
in the ordinary course of school life and recreation to explain the widespread natural immunity
acquired by the school as a whole.
Duration of immunity.
Work has been continued in following up children who have been actively immunised in
previous years. 1419 children have now been re-tested at periods ranging from 2 to 8 or more
years after the conclusion of their artificial immunisation by means of T.A.M. injections
(B.W. & Co.). The results of these re-tests are as follows:—
Still Schick-negative 1316
Reverted to some degree of positive reaction 103
Percentage of reversion to some degree of
susceptibility 7.2%
These results are eminently satisfactory when it is remembered that it has been shown recently
(Bousfield, Medical Officer, Jan. 1st, 1938), that of children immunised by means of a single
injection of A.P.T. 0.5 c.c. (Parke Davis), no less than 27.5% had reverted to the Schickpositive
state at the end of 10-12 months, many of them to a very marked degree. It appears
therefore that there is every reason to be satisfied with the fact that all immunisation done in
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