Tuberculosis Research Centre , Chennai
(2006)
Influence of sex, age & nontuberculous infection at intake on the
efficacy of BCG: re-analysis of 15-year data from a double-blind
randomized control trial in south India.
Indian Journal of Medical Research, 123 (Feb).
pp. 119-124.
ISSN 0971-5916
Abstract
Background & objectives: To estimate the efficacy of BCG in preventing tuberculosis over a 15-year
period, and also to assess the impact of infection with nontuberculous environmental mycobacteria
in a rural community in Chingleput district in Tamil Nadu in south India. We re-analysed the
15-year follow up data of a large randomized trial conducted earlier.
Methods: A double-blind randomized control trial was initiated in 1968, in which over 100,000
uninfected subjects with a normal radiograph were allocated to placebo, BCG in low dose (0.01 mg)
or BCG in high dose (1.0 mg); two widely used strains of BCG were employed, each in one half of
the vaccinated subjects. Sensitivity to purified protein derivative (PPD-B) was also determined.
The study population was followed for 15 yr by radiographic surveys of the total population once
every 2.5 yr, selective case finding in suspects once in 10 months, and investigation of those reporting
voluntarily with chest symptoms.
Results: Coverage by radiography was of the order of 80 per cent throughout, while coverage by
sputum examination of suspects was usually 90 per cent or above. The annual incidence of culturepositive
tuberculosis (irrespective of smear) was estimated to be 55 per 100,000, and neither strain
of BCG had any effect. The failure to protect was seen in both males and females, and in children
and adults. However, in a subset of over 40,000 subjects who were also nonreactors to PPD-B, BCG
had a low level of protection, i.e., 32 per cent (95% CI=3-52%), 29 per cent with the Danish strain
and 34 per cent with the French strain.
Interpretation & conclusion: Our findings reaffirm that BCG was of little value in preventing sputumpositive
cases of pulmonary tuberculosis.
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