THE BRITISH THORACIC AND TUBERCULOSIS ASSOCIATION

ANNUAL CONFERENCE

The Annual Conference was held on July 2nd-4th at the University of Lancaster. The meeting was held jointly with the Thoracic Society.

AUTHORS’ ABSTRACTS

A National Tuberculosis Mortality Survey (B.T.T.A. Research Committee Report)

P. D. B. DAVIES (London)

The full report will be published in the December number.

A Reappraisal of Control Measures TAN SUTHERLAND (London)

The work of the Tuberculosis Surveillance Research Unit has revealed the epidemiological importance of the risk of being infected with tubercle bacilli. Analysis of extensive tuberculin survey data has shown that there has been a steady and steep decrease in the risk of tuberculous infection in the Netherlands during the past fifty years; the annual risks of tuberculous infection in 1915, 1940 and 1965 were 8.7 %, 2.1 :? and 0.07 % respectively. Similar analyses have shown that the risk was also decreasing steadily in several other European countries before and during the second world war, whereas in a group of North African countries there was little or no change.

One important consequence of a downward trend in risk is the tendency for the infections to be concentrated into the early years of life of each cohort, implying that vaccination should be given soon after birth. Another is the tendency for the incidence of primary infections in adolescents and young adults to remain stable in the face of a decreasing risk of infection, until the annual risk has dropped below about 1%; this may explain why the high tuberculosis incidence at these ages in Europe and North America showed little improvement between the two world wars.

In Britain the risk of tuberculous infection appears to follow about three years behind that in the Netherlands; the estimated risk for 1970 is 0.050/o. In this situation the introduction of mass BCG vaccination in infancy would be unrealistic, and BCG, like miniature radiography, must soon come to be used more selectively than at present.

The aim in tuberculosis control must be to diminish the risk of infection to a greater extent between one year and the next than would otherwise have occurred: the problem is to decide which policies will be the most effective now in achieving this aim.

Surveillance in Countries with Low Prevalence PROFESSOR J. W. CROFTON (Edinburgh)

The apparently paradoxical situation that most tuberculous infection, for each particular cohort, occurs in childhood is not really surprising if one bears in mind the much smaller risk of infection in each succeeding cohort. One could put the paradox in another way: the older a patient is when he develops disease the younger he is likely to have been when he was first infected. Arising out of these observations there are three problems which require thought: (1) the specificity of the Heaf test, the main test now used in the U.K. ; (2) whether we should consider trying to lower the number infected by lowering the age of BCG administration; and (3) whether chemoprophylaxis might now be justified in the relatively small number of strongly tuberculin positive 1%year-olds if they