Though he was working in a potentially unprofitable field - vaccines for poor countries - he was able to pick up the sort of remuneration that is common to successful businessmen in the United States.

In 2001, according to VaxGen's annual report, Dr Francis was paid $325,000, with a bonus of $72,000, but he sold stock worth $2.9m, giving him a total take-home salary of $3.4m. He is thought to have grossed $7m in three years from the company, while his colleague Philip Berman, the inventor of AidsVax, grossed $5m.

In May 1998, the pair and one other executive were awarded a "success bonus" of stock options worth $7.9m between them after the VaxGen share price remained at $28 - four times the level when they launched the company - for 30 consecutive days.

It may be enough to arouse the envy of lesser-paid scientists, many of whom have been deeply critical of the ebullient talk at VaxGen about the prospects for the vaccine. It is certainly rather more than he would have earned earlier in his career as a government researcher working for the Centres for Disease Control.

During his 21 years there, Dr Francis is said to have played an important role in eradicating smallpox and led the effort to contain the world's first outbreak of Ebola. He was also one of the two principal investigators working on the clinical trials for a successful vaccine for hepatitis B.

On his retirement in 1992 from the CDC, he began to work with the major genetic engineering company Genentech, which in 1995 abandoned work on a tentative Aids vaccine and passed the plans to him.

He set up VaxGen specifically to develop it and threw himself into the effort to drum up financial backing and sell the idea.