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42
Active
immunisation.
Incidence of
diphtheria
where immunisation
has been
introduced.
Diphtheria
in "immunised
"
individuals.
As the result of Schick-testing, it was possible to separate the total of 7,567
into two groups, a naturally immune group of 4,925, and the unprotected minority,
numbering 2,642 (approximately 35 per cent, of the total), whom it was desirable
to protect by means of active immunisation through inoculation with antidiphtheria
prophylactic. Formol toxoid was employed for this purpose in three
subcutaneous injections of 0.2, 0.4 and 0.6 c.c. at intervals of 3 weeks between
the first and second and 2 weeks between the second and third doses. Reactions
following inoculations have proved negligible. Out of the total of 2,642 found
Schick positive and later inoculated, 2,332 or 88.3 per cent, proved to be Schick
negative or immune on subsequent Schick-testing about 4 to 6 weeks after completion
of the course of three inoculations. Of those remaining Schick positive and
therefore not yet protected, 78 were found to have become immune after receiving
a further course of formol toxoid, yielding a total of 2,410 immunised. There was
a balance of 232 children whose protection could not be completed by reason of their
having left school.
During the years 1932-35 there was, therefore, a total of 7,335 individuals,
who, for the time being, were known to be either naturally immune or who had
become protected by active immunisation.
During the four years under review, which include the various periods since
immunisation was begun in the individual schools, 274 children from the 24 residential
institutions where immunisation has been introduced were removed to hospital
as actual or suspected cases of diphtheria. As the result of subsequent findings these
cases may be classified in the following three groups: (1) in 36, or 13.1 per cent.,
the infection subsequently proved not to be diphtheria; (2) 84 yielded bacteriological,
but no clinical, evidence of diphtheria (of these 46 had not been Schicktested
while 38 had been tested, 25 proving negative and 13 positive ; 9 of the
latter had been immunised and later proved Schick negative; in the remaining 4,
immunisation had not been completed); (3) 154 were recognised as suffering from
clinical diphtheria, 108 of whom had not, for various reasons, been Schick-tested or
immunised. In 66 the parents had either refused or not given consent, and four proved
fatal; in 9 consent had been given, but the attacks developed before there had been
time to immunise the children; in 33, other illness had prevented their immunisation.
Of the 154 clinical cases 46 had been Schick-tested or had received prophylactic
inoculation. Nineteen had been found Schick negative at the time of testing,
these times ranging from as long as 7 years previously to as short a period as 1 week
prior to the attack of diphtheria developing. The intervals were: in one case
7 years, in 8 cases 1 to 3 years, in 6 cases 6 to 9 months, in 2 cases 1 and 3 months,
and in two cases only a week. The clinical type of diphtheria which occurred in
these 19 previously Schick negative cases was described as severe faucial in 2 cases,
faucial in 7, mild or modified faucial in 5, and nasal in 5 cases. None of the 19
Schick negative cases proved fatal.
Of the clinical cases, 27 had proved Schick positive, and 15 of them had received
the full immunising course of formol toxoid inoculation, and, after evidence of
successful immunisation, had subsequently been found Schick negative, at intervals
ranging from 4 years in 7 cases; 1 to 3 years in 3 cases; 11,9 and 3 months in
3 cases; and 1 month in 2 cases. The type of case was described as faucial or
clinical, but not severe, in 13 cases, and mild or modified diphtheria in 2 cases.
In the remaining 12 Schick positives, the immunising course had not been completed
before the onset of the attacks; the type of case in 10 of these was described as
mild 1, moderate 1, severe 1, nasal 4, faucial 3. None of the 27 cases originally
Schick positive proved fatal.