LONDON - Britain launched a mass vaccination programme to prevent the further spread of the H1N1 flu Wednesday, with officials urging healthcare workers and at-risk patients to be first in line.

The jab will be available to more than 11 million people deemed at highest risk from catching the H1N1 flu, who will be contacted by their doctors.

As well as health workers, those who it is suggested should take up the vaccination include all pregnant women, some over 65s and people who live with those who have weakened immune systems due to, for example, cancer treatment.

Patients will be vaccinated with Pandemrix, made by British drugmaker GlaxoSmithKline, which says it has received orders for 440 million doses ahead of the northern hemisphere's winter which could bring a second wave of the virus.

"This is the first pandemic for which we have had vaccine to protect people," said Liam Donaldson, the British government's top medical adviser.

"I urge everyone in the priority groups to have the vaccine - it will help prevent people in clinical risk groups from getting the H1N1 flu and the complications that may arise from it."

Britain is also offering H1N1 flu vaccinations to all its 9,000 troops in Afghanistan to protect them from a possible mass outbreak, the Ministry of Defence said last week.

Britain is the hardest hit country in Europe by the A(H1N1) virus. The number of Britons with the virus who have died has risen to 106, according to the latest figures, released last week.