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21
Infective Diseases.
which was returned as 81,114 at the 1921 Census, but they are an
indication that there is a certain demand for the service.
1,978 of the total number who attended were given the
Initial Schick Test to see if they were susceptible to Diphtheria,
and the remaining 687 were given immunising injections without
a preliminary Schick Test. Almost all of the latter were young
children, under five years of age, who were assumed to be susceptible
to Diphtheria on account of their age.
The Initial Schick Test:— An analysis of the results of
the tests performed is given in Table XIII. which shows the
cases divided into age groups and sexes and the result of the
test in each group. The last line of the Table gives the percentage
of the results found to be positive in each group
neglecting those in which the test was not read.
The essential fact brought out by this Table is that 1,429
persons gave a positive result to the initial Schick Test showing
that they were susceptible to Diphtheria. This is 72 per cent.
A glance at the last line of the Table will show that the
highest proportion of positive results was obtained at the lowest
age group and that the proportion diminished as age advanced.
This is in accordance with the known facts about the Schick
Test. On the other hand, an appreciable number of persons
over 15 years of age showed a positive result and more than
half of them were found to be susceptible. Even allowing for
the fact that most of the adults tested were young this proportion
appears to be high.
Immunisation:—In order to produce immunity three injections
have to be given at weekly intervals. Immunity does
not develop until several months have elapsed after the last injection,
and in order to determine whether this has occurred it
is essential for a further test—known as the Re-Schick Test—
to be performed. No person can be said to have been immunised
successfully until the re-test gives a negative result. Unfortunately
the exact period required to produce immunity varies
considerably and it is not possible to give an assurance that it
will take a certain time. After the last of the three immunising
injections has been given, parents are advised to bring their