Sir Liam Donaldson: ''This is rather a historic moment''
The first vaccinations in the UK-wide programme aimed at combating the spread of swine flu have begun.
Seriously ill hospital patients and the health staff caring for them will be the first of 14m people in the "priority group" to be given the jab.
From next week GPs will begin inviting people with health problems, damaged immune systems and pregnant women to come forward for immunisation.
However, concerns have been raised about the effect of the postal strike.
Sir Liam Donaldson, the government's chief medical officer, said the timing of the industrial action was unhelpful as GPs would be sending out appointment letters in the post.
But he added: "We are working very hard to try and get round that."
It is possible that appointment letters could be marked as urgent and prioritised for delivery or surgeries could use other forms of communication, such as the telephone.
Nonetheless, Sir Liam said the vaccination programme was starting just in time.
So far just over 100 people with swine flu have died in the UK out of about 500,000 who have been infected.
The spread of the virus peaked during the summer but in recent weeks the number of cases has started climbing again.
Schools in particular have been hard hit with significant local outbreaks being reported across the UK. One primary school in west Wales has even been forced to close this week because of the high number of staff shortages due to swine flu.
This is the first pandemic for which we have had vaccine to protect people. I urge everyone in the priority groups to have the vaccine
Sir Liam said: "It will help prevent them and their families getting the virus from patients, it will stop them passing the virus on to their patients, it will potentially protect them from mutated strains and it will reduce the disruption to NHS services caused by people being absent due to illness."
His comments were echoed by Dr Peter Carter, chief executive of the Royal College of Nursing.
He said: "It's important for them to keep well so that they are available to care for patients in the normal run of things, but if the pandemic really takes off we are going to need those nurses on the wards to help to cope with the influx of those that are seriously ill."
The vaccination programme represents a huge logistical challenge for the health service and is likely to take at least two months to complete.
It is being run at the same time as the seasonal flu campaign and has forced many GP surgeries to take on extra staff to cope with the workload.
There have been 108 swine flu-related deaths across the UK, with 83 deaths in England, 16 in Scotland, four in Wales and five in Northern Ireland
To 11 October, 4,735 swine flu-related deaths worldwide have been recorded by the World Health Organisation
The worldwide swine flu outbreak is officially the first flu pandemic for 40 years
But Professor Steve Field, president of the Royal College of GPs, said despite the scale of the programme, doctors were ready to immunise the priority groups.
"We have been planning for this for a while and everything is in place. We will be contacting patients in the coming weeks and they should wait for that."
There are two vaccines which will be used - one manufactured by GlaxoSmithKline and the other by Baxter.
The GSK one will be offered to most patients, while the Baxter vaccine is being generally reserved for people with egg allergies as the GSK jab was made using chicken eggs.
Most patients will require only one dose of the vaccine, although children and those receiving the Baxter version will need two doses, three weeks apart.
Under the system drawn up for GPs by the government, the priority groups have been ordered into four groups.
The under-65s with health problems and damaged immune systems, such as chemotherapy patients, will get the vaccine first.
They will be followed by pregnant women, then people who live with individuals who have compromised immune systems and, finally, those over 65 with health problems.
The government has yet to decide whether the rest of population will be immunised, although enough doses have been ordered.
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