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In addition, contacts of cases of tuberculosis were seen at the chest clinic and
were offered BCG vaccination. The figures are as follows:-

IMMUNITY INDEX
It is obviously desirable in connection with any prophylactic scheme to be able
to assess the degree of immunity conferred upon a community and this can only be achieved
by calculation of the proportion protected, as compared with the total, in a particular age
group. In the practical application of these requirements, the first problem arising is the
absence of any statistical data for the years prior to 1965 in such form that figures applicable
to the borough can be extracted from those compiled in the former London County Council
Division. It will, therefore, not be possible to prepare any reliable indices for the total
under-five age groups until after 1969. During the interim period, however, calculation
of percentage rates for each year can be made. These may be satisfactory as a working basis
for children in the first year or two of life, but may not be so for the upper age groups.
The population movements which take place at school entry age are sufficiently erratic to
render invalid an assumption that five-year-old residents or the children from the previous
year are the same individuals, containing in each group the same proportion of immunised
or vaccinated children. Thus such indices can only be a rough guide to the immunisation
state of school children and it is more effective for practical purposes for a constant check
to be made on individual school medical record cards.
However, an attempt has been made to calculate the percentage of infants who
have received their primary immunising courses for the usual diseases at least during their
first two years of life. This has been done by taking the number of live births for 1965,
subtracting the number of deaths and estimating the number of infants who would have reached
an eligible age and then seeing how many in fact were immunised. This method suggests
that approximately, sixty-four per cent. of infants received their primary course against
diphtheria, whooping cough and tetanus, and fifty-seven per cent. against poliomyelitis.
By using similar methods, just under thirty per cent. of infants have received primary vaccination
against smallpox by the age of two years.
These estimates show that there is undoubtedly room for a good deal of improvement
and every effort will have to be made to try and see that over seventy per cent. of
infants are protected, which is the normally accepted percentage if a serious outbreak is to
be prevented.