The risk of tuberculous infection in The Netherlands from 1967 to 1979

Estimates of the annual risks of tuberculous infection in the Netherlands from 1910 to 1966 were made by Stýblo et al. [1] from tuberculin surveys in recruits and schoolchildren. The risk decreased particularly steeply after about 1940 (the annual decrease in log risk was about 13%), and forward projections of the risk were made on this basis to 1980. Tuberculin test results in male recruits and in secondary or primary schoolchildren between 1966 and 1979 have now been used, alone and in conjunction with the earlier material, to estimate the trend in the risk of tuberculous infection in the Netherlands up to 1979, and to study the sex and age patterns in the risk. The risk of infection has continued to decrease steeply with calendar year in the Netherlands. Among the recruits the log risk, estimated only from the data from 1966 to 1979, decreased annually by 10.4%, compared with the estimate of 13.7% from the earlier data from 1956 to 1966; this difference is non-significant. Analysis of the complete data on schoolchildren from 1956 to 1979 shows a decrease in their log risk of infection of 15.0% each calendar year. The risks of infection were similar for boys and girls up to age 10, but were higher for boys than for girls (by 10.2%) during adolescence. In addition there was an increase in log risk of about 6.1% for each year of age up to age 20. According to this analysis, the annual risks of tuberculous infection in 1979 in the Netherlands were estimated to be 6, 9, 12, and 16 in 100 000 boys aged 5, 10, 15 and 20 years respectively, and 6, 9, 11 and 15 in 100 000 girls.