The elderly are being encouraged to keep warm and well

A quarter also mistakenly think healthy people do not need to have the vaccine.

The survey results were revealed as the Department of Health launched its annual campaign to persuade people over 65 to have their free jab.

People in "at-risk" groups, such as those with asthma and diabetes and those on steroids or cancer treatment are also advised to have the vaccine.

The survey of over 600 elderly people, carried out by NOP, also found almost half underestimated the number of deaths from flu and related illnesses each year.

Up to 4,000 people die from flu each year.

The Department of Health has set a target that 70% of the target group should have the flu jab.

Flu facts The virus can invade a million nose and throat cells in 12 hours A sneeze, which can carry the virus, travels at around 80 miles an hour and up to 30 feet 10 - 15% of the population may develop flu in any one year 150 million working days are lost to flu each year at a cost of �6.75 billion Between 3,000 and 4,000 people die from flu each year The worst flu outbreak ever, the 1918 pandemic, was the Spanish flu which killed at least 40 million people worldwide

Professor Sir Liam Donaldson, Chief Medical Officer for England, said: "After a series of mild winters, it is easy to be complacent about the threat of flu, but few realise that between 3,000 and 4,000 deaths are attributable to the complications of flu each year.

"Our message is a simple one - if you are aged 65 or over or in an 'at risk' group, for example if you have chronic asthma or diabetes, get your jab and stay well this winter.

"Don't let these myths discourage you from being vaccinated."

The Department of Health is also launching the Keep Warm Keep Well campaign, aimed at reducing the number of cold-related illnesses and deaths this winter.