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BCG vaccination may lessen the severity of, rather than completely prevent, serious forms of tuberculosis
In this issue of the journal (see pages 1550–4), Kumar et al report on the efficacy of bacillus Calmette Guerin (BCG) vaccination in favourably altering the course and outcome of tuberculous meningitis (TBM) in children. The value of BCG vaccination for preventing tuberculosis has been debated since its introduction nearly eight decades ago. Several trials, cohort studies, and case control studies have failed to provide a definitive answer to this contentious issue. A recent meta-analysis revealed that the protective effect of BCG vaccination in infants was only around 50% against all forms of tuberculosis.1 It has been suggested that although BCG vaccination is not highly effective in preventing the illness, it does play a role in reducing the severity of the more serious forms of the disease such as TBM.2 The authors of the present report set out to study this premise and also to document the presentation of the disease in vaccinated children. The strength of their work lies in the prospective collection of their data. The authors’ data suggest that children who had been vaccinated had a milder form of the disease and consequently had a better short term outcome than those who had not received vaccination. Vaccinated children also had fewer focal neurological deficits and higher cerebrospinal fluid (CSF) cell counts. The authors speculate that vaccinated children are probably capable of mounting a better immunological response than unvaccinated children (reflected in the higher CSF cell counts) and that this is responsible for the better outcome. It is, however, unclear from the authors’ data whether there were factors other than vaccination that contributed to the severity of the illness in the unvaccinated children. It is pertinent to note that the duration of the disease at presentation to the hospital in unvaccinated children was on an average 10 days longer than that in vaccinated children. Although this difference was not statistically significant, it suggests that parents of unvaccinated children tended to ignore early symptoms of the disease, thereby allowing the disease to progress in severity. This could be a reflection of the poorer socioeconomic status and lower educational background of the family which in turn could adversely affect the severity of the disease and its outcome. A more comprehensive and in depth study of the socioeconomic parameters of the families of the children, the nutritional status of the children, and a longer follow up period (the outcome was studied at discharge from hospital) would have strengthened this paper. These deficiencies apart, this study adds to the body of literature that indicates that the utility of BCG vaccination lies more in influencing the severity of the serious forms of the disease, such as TBM, than in providing absolute protection against the disease. In doing so, it supports the continuation of BCG vaccination as a part of the Universal Immunization Programme (UIP) in endemic countries such as India.
BCG vaccination may lessen the severity of, rather than completely prevent, serious forms of tuberculosis
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Competing interests: none declared