A re-examination of the variations in the efficacy of BCG vaccination against tuberculosis in clinical trials.

Setting: The findings of the principal controlled trials of BCG vaccination against tuberculosis are reviewed.

Objective: To investigate possible reasons for the wide variations in vaccine efficacy in different trials, and in particular for the apparent adverse effect in the first few years in the trial in Chingleput, South India.

Observations: (1) A substantial reduction, or even a reversal, of overall efficacy could result if the assessment of vaccine efficacy included a subgroup adversely affected by vaccination.

Tuberculosis notification rates in the elderly.

The highest rate of tuberculosis notification in England and Wales during the 1980s occurred in males aged 65 years and over. This is explained on the basis of reactivation rather than recent infection: a trend which is likely to continue until the end of the century.

The effects of the scheme for BCG vaccination of schoolchildren in England and Wales and the consequences of discontinuing the scheme at various dates.

The aims of this paper were to estimate the numbers of tuberculosis notifications in young white adults which will be prevented in the next 25 years by the schools BCG vaccination scheme, and to assess the numbers of additional notifications if the scheme were to be discontinued. Assuming that in the white ethnic group in England and Wales the decline in tuberculosis notification rates (8-10% per year for ages less than 45 years) and efficacy of BCG vaccination (75-80%) are maintained, it is estimated that the scheme for BCG vaccination of schoolchildren with its present coverage will prevent 217 notifications in those aged 15-29 years in 1993, 119 in 1998, and 69 in 2003. The epidemiological consequences of stopping the BCG in schools scheme, whenever this occurs, would be a substantial slowing of the rate of decline of tuberculosis notifications, confined almost entirely to the 15-29 years age group, for a period of about 15 years, after which the steeper decline would resume.