What Is the Best Way to Use BCG to Protect against Leprosy : When , for Whom , and How

tection against leprosy addressed the question of whether or not BCG was effective against leprosy. BCG vaccine trials against leprosy in South America, Africa, and Asia have demonstrated that the BCG vaccine protects against leprosy (). However the degree of protection conferred by BCG is variable between different populations as is its efficacy in the prevention of tuberculosis (). Repeated doses of BCG confer additional protection against leprosy, but probably not against tuberculosis ( ). The issue now is not whether BCG is effective but rather what is the best way to use BCG to protect against leprosy? Who should be vaccinated, when should they be vaccinated and how often? In this issue of the INTERNATIONAL JOURNAL OF LEPROSY, Sergio Cunha and colleagues describe a trial to compare two different BCG vaccination strategies. The one currently recommended in Brazil which is population neonatal BCG vaccination and vaccination of household contacts of leprosy patients, versus population neonatal BCG vaccination and vaccination of all school children aged 7 to 14 years. Neonatal BCG vaccination is recommended in Brazil to protect against tuberculosis. The fact that BCG also protects against leprosy is a bonus. Indeed the degree of protection against leprosy may be greater than that conferred against tuberculosis (). It would be difficult to justify the use of BCG at a population level on the basis of protection against leprosy alone because of the very low incidence rates of leprosy. The leprosy community is very supportive () of the continued use of BCG in leprosy endemic countries, particularly when the costs of the BCG vaccination program are not charged against the limited leprosy budget. The widespread use of BCG vaccine with high population coverage is considered to be a very important factor in the decline in the new case detection rates of leprosy observed in many countries. It is also estimated that the continued use of BCG will be a critical factor affecting the long term trends in incidence rate of leprosy (). The lack of a consistent protective effect of BCG re-vaccination against tuberculosis makes the policy of routine BCG revaccination in the whole population less economically viable. The most recent World Health Organization Expert Committee on Leprosy () did not recommend routine repeated doses of BCG to prevent leprosy because of poor cost-effectiveness, lack of acceptability to recipients, operational difficulties, and the fact that the vaccine (BCG is a live vaccine) is contra-indicated in patients showing symptoms of HIV infection. In Brazil, neonatal BCG vaccination and selective BCG re-vaccination of household contacts of leprosy patients is recommended. The trial described by Sergio Cunha in this issue sets out to compare this current BCG strategy with an approach where all school age children are re-vaccinated. Similar research questions are being explored in the use of chemoprophylaxis (); should chemoprophylaxis be give to whole communities or selectively to household contacts (). A meta-analysis of chemoprophylaxis trials suggests that community coverage has greater efficacy but that selective household contact strategies are more cost effective (). Analysis of the numbers needed to vaccination to prevent one case gives a simple esti1 This article was received for publication 30 November 2003. It was accepted for publication 20 January 2004. Reprint requests to: Professor of Public Health and Head of Department of Public Health, Polwarth Building, Medical School, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland. E-mail: [email protected] COMMENTARY