|BCG VACCINATION INDURATION SIZE AS AN INDICATOR
OF INFECTION WITH MYCOBACTERIUM TUBERCULOSIS
|GD Gothi, SS Nair, Kul Bhushan, GVJ Baily & GE
Rupert Samuel: Indian J TB 1974, 21, 145-51.
After the introduction of direct BCG vaccination,
assessment of post-vaccination allergy and information about prevalence
of infection could not be obtained. Few methods were tested i.e.,
i) retesting of persons with 0-13 mm reaction at site of vaccination
on 4th day of vaccination, ii) retesting of all vaccinated persons
of age 0-10 years. It is not only necessary to find out the size
of BCG lesion that could separate them but also the day after vaccination
on which the tuberculin reaction size best correlates with the BCG
vaccination size. With this in view, two studies with regard to
direct BCG vaccination done in India have been examined further.
In Study I, 816 eligible persons were tested with 1 TU RT
23 read on 3rd day and vaccinated with either Indian or Danish vaccine.
The vaccination lesions were examined on the 3rd, 6th and 90th day
of vaccination. On the 90th day post-vaccination tuberculin test
was done and read on 3rd day. In Study II, a total of 691
who had no previous BCG scar were simultaneously tuberculin tested
with 1 TU RT 23 and vaccinated with either Indian or Danish vaccine.
The BCG lesions were examined every day and on 39th and 90th day.
The correlation of pre-vaccination tuberculin
test and BCG lesion size showe d that sixth day in first study
and fifth day in second study was the highest. Tuberculin reaction
size of 10 mm or more correlated well with 14 mm or more induration
size of BCG in classifying the persons as infected and non-infected.
Correlation between the size of BCG scar at 3 months and size of
pre-vaccination tuberculin reaction was poor. Considering the two
studies together vaccination induration of 14 mm or more on 5th
or 6th day appears to be the best criterion for demarcating the
infected from non-infected. Some other choices are 12 or 14 mm levels
on 2nd day, 10 and 12 mm levels on 5th day and 10 mm levels on 8th
day seems to be nearly as good and operationally useful.
A BCG Vaccination induration size of 14 mm and
above between 5th and 6th day of vaccination, for all practical
purposes may be considered satisfactory for demarcating persons
infected with M.tuberculosis from those non-infected. It can
be concluded that estimation of prevalence of infection,
when BCG vaccination is given to all without prior tuberculin testing,
can be made on the basis of BCG vaccination induration size of 14
mm or more.
|KEY WORDS: BCG VACCINATION, M.TUBERCULOSIS,
INFECTION, TUBERCULIN INDURATION, RURAL POPULATION.