By Nick Triggle
Health reporter, BBC News
Parents on whether they will get their under-fives vaccinated
Children under the age of five are the next in line to get the swine flu vaccine, the government has announced.
The immunisation programme is already well under way, with NHS workers, pregnant women and people with health problems being offered the jab first.
The UK-wide programme will be extended to children aged from six months up to five years from December after a recent rise in serious illnesses.
People caring for elderly or disabled people will also be offered the jab.
The move to vaccinate children was widely expected, although some people had suggested there might be a mass schools vaccination campaign.
The Conservatives have already said all under-25s should get the jab next.
However, on the advice of its vaccination experts, the government decided to concentrate on the youngest age groups.
Chief Medical Officer Sir Liam Donaldson said there had been a rise in serious illnesses recently among young children that was "causing concern".
"We consider them to be seriously at risk.
"Parents are standing by intensive care beds in life and death situations.
"We are out to save lives and fight this pandemic all the way."
The number of under-fives currently in hospital is still fairly low - fewer than 200 in England. But they are three times more likely than other age group to need hospital care.
And the overwhelming majority of those children requiring hospital treatment - 81% - were previously healthy.
The vaccination move comes as the number of infections fell in England for the second week in a row.
There were 53,000 new cases last week, compared with 64,000 the week before.
New cases are also dropping elsewhere in the UK.
Sir Liam said it was "too early" to tell if the pandemic had peaked because the numbers in hospital remained relatively high.
The first wave of vaccinations, which is being offered to nearly 14m people, is not expected to be finished until Christmas.
Children under five are expected to get the vaccine from December
However, there is likely to be some overlap, with GPs likely to be asked to start giving immunisations to children once they are close to completing the initial priority groups.
There are more than three million children under the age of five.
Meanwhile, at least 1.5m carers will be offered the jab as experts felt there could serious consequences for vulnerable people if they fell ill.
But a BBC poll this week showed the scale of the problem the government faces convincing people to agree to vaccination.
There are no official take-up figures yet, but the survey of more than 2,000 showed nearly half had doubts about getting immunised.
Safety and the mildness of the virus were the major concerns.
Professor Steve Field of the Royal College of GPs said: "We shouldn't underestimate swine flu - it is a nasty infection and its effects can be devastating.
"I know that some parents have concerns about immunisation, but the swine flu vaccine is our most effective protection."
The two different types of vaccine being used in the UK have been through clinical trials and approved by the official European drugs regulator.
The World Health Organization's monitoring of problems following swine flu vaccination also indicates swine flu vaccines have a good safety record.
WHO vaccine expert Marie-Paule Kieny said: "Reporting so far reconfirms that the pandemic flu vaccine is as safe as the seasonal flu vaccine."