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24
Report of the Medical Officer of Health for 1929.
positive result before the final negative reading. The negative
results only are recorded in Table XV. This Table shows
that in 730 instances the negative result was obtained within
six months of the completion of the first series of injections.
It also shows that three injections were generally sufficient to
produce immunity but that a second series was required in a
few instances.
131 persons who completed the first series of injections still
gave a positive result when re-tested and were therefore not
protected. Full details of these are given in Table XVI. Some
of these persons have moved to other districts or have imtimated
that they do not propose to complete the course. Some of
them, on the other hand, are still under observation and will
probably continue to attend for further injections and tests.
This group of 131 includes 99 persons who showed a positive
re-Schick Test after the first series of injections and have
not attended since. The other 32 persons have received a
second series of injections and 28 of them have not yet been retested,
while in four the re-test is still positive.
At the present time it has not been necessary to give a third
series of injections, but the fact that positive tests are still
obtained, in a few instances, after the second series suggests
that further injections will be required in some of them.
Further evidence of the delay which occurs sometimes in
the production of immunity is obtainable from Table XVI.
It will be seen that in several instances a positive re-test was
obtained more than a year after the completion of the first
series of injections and that three children showed a positive
result over 2 years afterwards.
The 256 persons who received three immunising injections
may or may not be completely protected but they cannot be
returned as such in the absence of a negative re-Schick Test.
Diphtheria Following Immunising Injections:—Owing to
the fact that immunity does not develop at once it is important
to remember that a child may develop Diphtheria during the