A CONTROLLED TRIAL OF COMMUNITY-WIDE ISONIAZID PROPHYLAXIS IN ALASKA

Abstract

In 1957, a controlled trial of isoniazid prophylasis was initiated in 30 communities in the Bethel area of Alaska, where tuberculosis rates were among the highest ever reported. More than 85% of the total population of 7,333 persons participated in the trial. Most of the non-participants were excluded because they were being treated for tuberculosis or because they came to the study communities late in the medication year; only 3% refused to participate. Half of the participants were randomly allocated to the placebo group and half to the isoniazid group, the latter drug being prescribed in a dosage of 5 mg/kg of body weight daily for one year. The median length of observation is now almost 6 years. The risk of active tuberculosis developing during the study period was greatest among young adults, among positive reactors to tuberculin, and among persons with initial evidence of tuberculosis for which treatment did not then seem to be indicated. For all groups this risk was substantially decreased by isoniazid prophylaxis. The reduction in tuberculosis attributable to isoniazid persisted essentially unchanged throughout the entire period of observation, averaging about 60%. Although protection was greatest among persons who took medication regularly for a full year, some protection was noted even among persons who took isoniazid irregularly and for short periods. Each year of personnel time invested in a program of community-wide prophylaxis resulted in the prevention of 10 cases of tuberculosis, accounting for 100 person-months of hospitali-zation. Community-wide prophylaxis is feasible under conditions similar to those in Alaskan villages.