vaccine maker Acambis swung to a third-quarter profit yesterday as it sold smallpox jabs to the United States and said its pipeline of experimental drugs was progressing well, boosting its shares.

The company, whose fortunes have been transformed by contracts to supply 209 million doses of smallpox vaccine to the United States, also confirmed that John Brown, its Scottish-born chief executive, will step down at the end of the year.

Brown will be succeeded by Gordon Cameron, chief financial officer, until a permanent replacement is found in the early months of 2004.

Acambis made a pre-tax profit of (pounds) 22.2m in the three months to September 30, compared with a loss of (pounds) 1.3m in the same period of 2002. Revenues more than quadrupled to (pounds) 65.8m.