More than 80 per cent of young children are admitted to hospital with swine flu were previously healthy, figures showed today.

An analysis of patients needing inpatient treatment in England also showed that almost half of people aged 16-44 had no previous underlying health conditions before being admitted, official figures suggested.

It comes as the number of new cases diagnosed last week rose to 14,000 as the expected second wave takes hold.

Meanwhile preparations are under way to vaccinate 13 million people who are in priority groups or are front line health and social care workers before Christmas.

A letter to the NHS from Dr David Salisbury, head of immunization at the Department of Health, said the first batches of vaccine will arrive in hospitals on October 14th at the earliest to be offered to staff and the earliest GPs will receive vaccine will be October 19th.

All GP surgeries should have received vaccine by November 9th although this depends on deliveries from the makers, GlaxoSmithKline, the letter said.

Chief medical officer Sir Liam Donaldson also announced today that a number of specialized beds to treat people with severe lung failure will be doubled for adults, from five beds to 10, at a specialist unit in Leicester.