Sir

John Moore's review of E. Hooper's The River (Nature 401, 325–6; 1999), on the possible link between the origin of HIV and a contaminated polio vaccine used during a mass vaccination campaign in equatorial Africa in the 1950s, carefully discussed the weakness of the book's hypothesis. But it is important to add that the polio vaccine currently being used worldwide is safe.

This message was not very clear when newspapers in Uganda first picked up the HIV–polio theory from the US media some years ago. As a result, some people thought that their child would be given a contaminated vaccine. So they kept their children from being vaccinated, putting them at high risk of poliomyelitis. In 1999, there were 49 confirmed polio cases in Uganda, according to the World Health Organization.

With the recent renewal of interest in the HIV–polio theory, there is a need to stress the safety of the present polio vaccine whenever it is discussed. Hopes for global eradication of polio depend largely on vaccination coverage in all parts of the world.