It is important that small children be kept away from this disease as
long as possible. It is particularly difficult to limit the spread of
the disease by isolation because the period of greatest contagiousness
is that in the beginning when the child is supposed to have a cold. An
older child in a family contracts the disease at school or in play with
other children, and before he is suspected of having the disease, the
younger members of the family have been infected. A vaccine has been
prepared from the bacillus of whooping cough which appears to have
some value in preventing and rendering milder the disease. As this is
harmless it ought to be given to young children as soon after exposure
as possible in the hope that it may prevent the disease or make it
milder if it develops. After the paroxysms have been established the
vaccine seems to be less useful.