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54
After many observations it has been generally concluded
that anti-diphtheria immunisation is harmless. The immunity
develops slowly bat is of a more or less permanent character.
This can be definitely demonstrated by means of the Schick test
after three months. The maximum immunity is not obtained until
after the expiration of at least six months after the three injections.
Zingher found that after toxin-anti-toxin injections 30%
gave a negative Schick reaction after 2 months, 51% after 2½ months
and 87% after five months.
The protection cannot always be said to be absolute in all
cases but it can be said to be as complete as any form of specific
protection such as vaccination against smallpox or inoculation
against typhoid. It can be said that from 90 to 95 per cent. receive
complete protection. If however an immunised subject happens
to be attacked with diphtheria the condition is quite a mild one
of a transient nature.
Zingher and Schroder have examined 106 children injected
3 to 6½ years previously, subjecting them year after year to the
Schick test. All the children concerned remained negative to the
test showing the immunity acquired to be more or less permanent.
The incidence of diphtheria in New York is greater than in
any town in this country, which possibly accounts for the active
steps taken in regard to its control, and very large numbers of
school children have been injected and kept under observation.
The following figures supplied from that source are therefore
interesting:— No. of Cases of
Diphtheria
57,000 school children, negative Schick reaction 5
33,000 school children, positive Schick reaction
but immunised 9
90,000 school children, negative Schick reaction
or immunised 14
90,000 school children used as controls 56