NEW YORK — Cuba's announcement that its scientists have developed a vaccine to improve the lives of lung-cancer patients is reason for optimism. Cautious optimism is in order, though, since previous claims have been made before by several scientists in dealing with this disease — claims that later proved unfounded.

In 1991 I headed a U.N. mission to Cuba of Latin American physicians. We were asked to evaluate Cuba's production of interferon, an anti-viral substance, and its applications. We were gladly surprised at the excellent technical level attained by Cuban scientists and the progress they had made in producing interferon.

During a visit to our group, Fidel Castro showed considerable enthusiasm for Cuba's advances in public health projects. So, the reported advances on a lung-cancer vaccine did not surprise me. Since the late 1980s, following visits by doctors from M.D. Anderson Cancer Center in Houston to Havana, the Cuban government had chosen biotechnology as a priority area for development.