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It is nevertheless clear that had we in this district not been
testing all the children after inoculation, no less than 31 in every
hundred would not have been successfully immunised, and what
is even worse, would probably have been misled into believing
that they were protected against diphtheria.
Method 2. Schick positive children immunised by means of
two injections of A.P.T. 0.2 c.c. and 0.5 c.c. at 14 days interval.
Re-tests performed from 3 to 5 months after the last injection.
Number re-tested to date 143
Number re-Schick negative 135
Number still Schick positive 8
Percentage of failure to immunise by this
method 5.9
It is thus clear that the two injection method is very much
more satisfactory than the single injection procedure. The
work tends to show that the brand of A.P.T. used in these tests
has no advantages over other makes we have used, and we find
no evidence at all that it is an antigen of greater power than
other makes which would render its use as a single injection
prophylactic either desirable or even justifiable.
For the purpose of making these figures of greater value,
it may be stated that primary Schick tests show that the herd
immunity in this area is not great, being only in the region of
10 per cent. natural Schick negative rate. Still this is the
rate which experience has shown now obtains in and around
many areas of London, and the work tends to show that single
injection prophylaxis is not satisfactory in the environs of
London."