High risk patients and frontline health workers in hospitals will begin being vaccinated against swine flu on 21 October, chief medical officer Sir Liam Donaldson has announced.

Sir Liam’s announcement came as the number of swine flu related deaths in the UK reached 106.

During his regular weekly briefing at the Department of Health, Sir Liam said there had been 83 deaths in England, 15 in Scotland, four in Wales and four in Northern Ireland.

Sir Liam said: “There is a further increase but the increase has not been anything like the doubling expected.”

The number of people in hospital with the virus increased from 290 to 364, while the number in intensive care rose from 47 to 74.

The proportion of hospitalised patients in intensive care is the highest since the epidemic began, Sir Liam said.

He added: “For most of the time it’s been about 12-13 per cent, now it’s up to 20 per cent, suggesting we are seeing more serious cases than we were seeing before. There is no sign of any change in the virus but this is giving me some concern.”

About 37,000 people have contracted the virus so far in the UK, according to the Health Protection Agency.