Tuberculin sensitivity

SUMMARY

A prospective study of tuberculin sensitivity has been conducted among 3610 subjects under 20 years old in the Solomon Islands, Western Province. Mantoux positivity (⩾5 mm induration after 5 TU) fell from 81% during the 6 months following birth BCG vaccination to 13% for children aged 1–8 years of age among whom it was not significantly higher than the rate of 9% noted for unvaccinated subjects. Birth BCG does not, therefore, hinder the diagnostic usefulness of tuberculin testing for such children. For the study population as a whole, BCG-induced Mantoux positivity was restricted to induration under 15 mm diameter. Stronger responses were considered specific for tuberculin infection and indicated a prevalence rate that rose from 2% to 16% with age. Accelerated BCG reactions recorded among 45% of 162 tuberculin non-reactors under 8 years old indicated that the waning of tuberculin responsiveness at this time could not be equated with loss of clinical protection against tuberculosis.