Tuberculin sensitivity in rural Gambian children

A tuberculin survey was undertaken in 480 Gambian children under the age of 10 years, resident in a group of villages where BCG vaccination, shortly after birth, has been widely practised for about 5 years. Ten tuberculin units of purified protein derivative were given by needle and syringe; reactions of 3 mm or greater were considered positive. An overall tuberculin positivity rate of 59% was found which varied little with age, sex or village size. Among children who had probably not had BCG vaccination the positivity rate was about 20% with an annual increase of approximately 5%. Among children who had probably been vaccinated with BCG the positivity rate was between 60% and 80%. There was a fall in the prevalence of positivity of about 10-20% during the first year after vaccination. Thereafter, positivity rates were well maintained for at least another 5 years.