Efforts to prevent diphtheria take two main directions. In one the
object is to prevent the infection of new persons; in the other the
measures employed are used to render well persons immune to the
disease so that they will not become sick even if the germs reach
them. Prevention of the infection of other persons is accomplished by
isolation or quarantine of the sick individual and his attendant. To be
effective quarantine must be carried out with conscientious attention
to the smallest details. When a member of a family develops diphtheria,
other members of the household may permanently leave the house if they
are free of diphtheria germs as shown by cultures. The way in which
quarantine is carried on has been described as it relates to all the
diseases under discussion. In the case of diphtheria quarantine can
only be terminated when repeated cultures from the throat and nose
have shown that the diphtheria bacilli have disappeared. This may
require several weeks and in exceptional cases even months. Carriers
must be placed in quarantine as well as active cases. As recovery from
diphtheria progresses the germs tend to die out and often are no longer
present after a few days. Sometimes the germs persist and the patient
becomes a persistent carrier. In the persistent carrier usually some
abnormal condition in the nose and throat interferes with the efforts
of nature to destroy the germs. When such are corrected the germs often
quickly disappear. Most often diseased adenoids and tonsils are the
offending conditions. In this case the removal of abnormal adenoids
and tonsils is usually followed by prompt disappearance of the germs.
Persistence of bacilli in the nose of children has sometimes been
dependent on the presence of foreign bodies such as shoe buttons.
Aside from the measures outlined which have for their purpose the
prevention of extension of the germs to other persons, important steps
may be taken to render persons immune to diphtheria so that they will
not be affected by the germs. This is accomplished in two ways. In the
presence of immediate danger, small doses of antitoxin at intervals of
three to four weeks procure protection. This is to be selected when
children in a family cannot be protected from infection by quarantine.
When immediate danger is absent an immunity which lasts for years may
be secured by a sort of vaccination. This consists of three hypodermic
injections at intervals of a week of a mixture of diphtheria toxin
and antitoxin. The amount injected is very small and produces little
or no inconvenience, but it is followed in a few weeks by a lasting
protection against future infections. Almost all persons become immune
after such injections. Such vaccinations have been used in a large
scale among school children in New York City. Among 90,000 school
children thus treated only one-fourth as many cases of diphtheria
occurred last year as among the same number who refused the treatment.
Injections are advised in children as early as possible after six
months of age is reached. If this were uniformly employed children
would be protected against diphtheria during the most susceptible
years, and the disease would largely disappear. It is not too much to
hope that this vaccination measure against this most fatal disease of
children will accomplish corresponding favorable results to those which
have followed vaccination against small pox.
It is not desirable or necessary to use such injections in children
who are already immune. By a simple harmless test it is possible to
determine if susceptibility exists in the individual. This is known
as the Schick test. It is easily given and is devoid of all danger
and discomfort. Such tests have shown that the proportion of persons
susceptible to diphtheria varies with age. Few infants under six
months are susceptible. From one to three years about 60 per cent are
susceptible. As age advances the proportion gradually decreases so
that by 20 years only about 20 per cent are liable to be infected if
opportunity occurs. The children in the families of the well-to-do are
susceptible in larger proportions than are those living in crowded
parts of cities, and in country districts the proportion of susceptible
children is very high.