What’s the need?

The study reported by Moet et al found benefit at two years after rifampicin, but did not find any significant difference between rifampicin chemoprophylaxis and placebo treatment in the third and fourth years after rifampicin treatment.¹ Mycobacterium leprae multiplies very slowly, and the incubation period of leprosy is about five years but can be up to 20 years (www.who.int/mediacentre/factsheets/fs101/en/index.html). Whether the absence of clinical cases of leprosy at two years after rifampicin treatment is due to rifampicin chemoprophylaxis or just due to subclinical infection within the incubation period can therefore not be established.

Any benefit of rifampicin chemoprophylaxis would not exceed 50% under routine conditions.² In the absence of any long term benefit, individuals at high risk could immediately be reinfected with M leprae as long as transmission persists after the immediate benefit has waned.³

The finding¹ that patients with low risk for leprosy, on the basis of physical distance, genetic relationship, age, and leprosy classification,⁴ benefited more from rifampicin chemoprophylaxis is not surprising because contacts who are not at close physical distance from the patient are not close contacts at all. Leprosy is not highly infectious (www.who.int/topics/leprosy/en/); transmission occurs through droplets from the nose and mouth of untreated patients with severe disease. The contribution of close household contacts to the total number of new leprosy cases in a population is about 30%, and the chemoprophylaxis benefit of these household contacts is only 15%.² To prevent a single case of leprosy, hundreds or even thousands of contacts need to be treated.² The cost and operational difficulties to apply chemoprophylaxis to a large population will be extremely high, although the yield will be limited.²

The World Health Organization’s strategy of promoting early detection, diagnosis, and treatment of leprosy, not chemoprophylaxis, seems right at this time.