Dr. Comstock’s most well known achievements in public health were in the field of tuberculosis and his thoughtfully executed field trials have left an indelible legacy. Upon joining the US Public Health Service Tuberculosis Program in 1957, Comstock organized field trials to investigate the BCG vaccine in Muscogee County, Georgia and Puerto Rico, showing a low overall efficacy of BCG. As a consequence BCG was never formally adopted as a control strategy in the US. In the mid-1950s Dr. Comstock organized one of the first cluster-randomized trials in medical history, a trial of isoniazid preventive chemotherapy in the Bethel region in Alaska, where a tuberculosis epidemic was ravaging the native population. After one year, tuberculosis incidence was reduced 69% in the isoniazid households, and this benefit was sustained through 5 years of follow-up. After the 5 year follow-up, Comstock made the decision to provide all participating households a year of therapy, regardless of prior study arm. This ethical approach led to further analyses suggesting that 9 months of isoniazid preventive therapy is the most effective duration and is still the current recommendation.
Though Comstock was proud to say that he was the only professor at Johns Hopkins School of Public Health to have instructed each of the core Epidemiology courses, he was most proud of his beloved “Epidemiologic Basis for Tuberculosis Control” which he instructed for over 40 years. TB controllers from around the world came to Hopkins for his 3 week summer version of the course. Through this course he extolled his wisdom and vast experiences to hundreds of public health students who have implemented TB control programs across the globe.