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....