* H1N1 vaccination to start in October
* GlaxoSmithKline seen as main supplier

LONDON, England - Britain's swine flu vaccination programme is to start in October for at-risk groups, Chief Medical Officer Liam Donaldson said on Thursday, with most vaccines coming from drugs firm GlaxoSmithKline.

A first batch of 300,000 vaccines will arrive this month with 54.6 million expected by December, Donaldson said, adding that exact supply levels would depend on the manufacturers.

"We are getting a lower supply from Baxter than we had envisaged so the majority of our vaccines will come from Glaxo," Donaldson told reporters.

Earlier this month, the World Health Organisation said it expected the first vaccines to combat H1N1 flu to be ready for use in some countries from September.

Donaldson said the treatments would need to be approved by European medical regulators before vaccinations begin.

"In October we expect, provided the license is granted, to be able to give the first shots of vaccine," he said.

The pace of new H1N1 infections in Britain has eased in recent weeks, with doctor consultations for flu-like illness falling by 34 percent last week.

The majority of cases have proven to be mild and the government plans to slash the number of flu call centre staff from around 1,600 to less than 600 by Aug. 23 because of the sharp drop in suspected infections.

But health experts expect another surge later in the year.

"We have seen an increase in the proportion of deaths amoung previously healthy people," Donaldson said, adding that five of the eight new deaths in England over the last week were of otherwise healthy people.

"It is causing more deaths in healthy people than seasonal flu," he said.

Fears the strain could become resistant to anti-viral drug Tamiflu have underscored the need to get vaccines to market quickly.

The government plans to immunise about 11 million people seen as most at risk first because it does not expect to have enough doses for the whole population before winter.

The first to be immunised will include about 5 million people aged over six months in current seasonal flu risk groups, all pregnant women, contacts of people with compromised immune systems, and about 2 million health and social care workers.

Healthy people over 65 will not be prioritised because they appear to have some natural immunity to the virus, the Department of Health said