Interventions for Tuberculosis Control and Elimination 2002

year following commencement of treatment was 22%. For reasons that are
not understood, there was no protection observed in those aged less than
25 years, in contrast to 56% protection in those aged 25 to 34 years, and
intermediate protection in the other age groups.
Prevention of disease in persons with risk factors
The risk of tuberculosis among persons with long-standing tuberculous infection
(those studied in the above presented trials) is fairly small, thus the
effectiveness of a preventive chemotherapy scheme is relatively modest.
Conversely, it is of special interest to study the efficacy of isoniazid preventive
chemotherapy in persons with a recognized increased risk of tuberculosis,
because the attributable fraction of cases that can be prevented is
relatively large if the prevalence of the risk factor is also high.
Recently acquired infection
Recently acquired tuberculous infection is not only associated with an
increased risk of progression to tuberculosis, but it is also a frequent event.
Four studies of preventive chemotherapy among contacts of newly diagnosed
index cases of tuberculosis are selected here to illustrate the point
(figure 78). 878-881
In April 1960, a patient with pulmonary tuberculosis in a marine camp
of the Royal Netherlands Navy infected a large number of his mates in a
Netherlands Navy
Kenya
USA
Japan
- 50 0 50 70 90 95
Protection (%) (log scale)
Figure 78. Protection from isoniazid preventive therapy against tuberculosis among
contacts of tuberculosis patients. 878-881
130