The flu vaccine given to millions of people each year in Britain is “over-promoted” and “over-hyped” and the protection it offers against the seasonal illness has been exaggerated, scientists claim.

Flu causes thousands of deaths, mainly among the elderly, in the UK each year but the vaccine is of limited effectiveness, especially for older people. One expert told The Independent the Government should be held accountable for “wasting taxpayer’s money” on the annual £120m national vaccination campaign.

But scientists stressed it was still worth getting the jab as it is currently “the best we have”.

A report published by the Centre for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota, US, says the misperception that existing flu vaccines are highly effective has become a barrier to developing new and better vaccines.

It also risks undermining public trust in mass immunisation campaigns if Governments fail to tell the truth about the vaccine.

Michael Osterholm, director of CIDRAP and professor of Environmental Health Sciences, said: “I have been a strong proponent of vaccination in general and flu vaccine in particular for many years. I still recommend its use as the best we have. But we have over-promoted this vaccine. For certain age groups in some years its effectiveness has been severely limited relative to what has been previously reported.”

The vaccine is offered free on the NHS to everyone in the UK over 65, to patients of all ages with chronic illnesses such as asthma, to pregnant women and front-line healthcare workers in what is an annual bonanza for drug companies.

Latest figures from the Health Protection Agency show 60.8 per cent of over-65s have had their flu shot this winter and 37.5 per cent of those with chronic illnesses. Among pregnant women uptake is running at 29.8 per cent with healthcare workers at 28.4 per cent.

Flu vaccine has to be re-formulated every year on the basis of an educated guess by experts who attempt to match it with the strains of the rapidly mutating flu virus likely to be circulating that season.

A 2010 review by the highly respected Cochrane Collaboration, an international network of experts, concluded that the vaccine had little impact in years, like the winter of 2011-12, when the vaccine and the viruses were mismatched.

On average, flu vaccine shortened the illness by about half a day but did not reduce the number of people hospitalised, it said.

Tom Jefferson, an author of the Cochrane reviews, said: “We have conducted four reviews since the late 1990s. We calculated that you need to vaccinate between 33 and 99 people to prevent one case of flu, depending on the match between the vaccine and the circulating strains of the virus. I want people held accountable for wasting taxpayer’s money on these vaccines. The reviews have been available for years and nothing has been done.”

Influenza vaccine was first introduced in the 1940s and protection rates of between 70 to 90 per cent were frequently cited. The CIDRAP report found that the flu shots given in the UK, using trivalent inactivated flu vaccine, provided 59 per cent protection in healthy adults aged 18 to 64 but there were no good studies demonstrating its effectiveness in adults of 65 and over.

Professor Osterholm, an US public health adviser whose report “The Compelling need for game changing influenza vaccines” was published last month, said: “Our report is very comprehensive. It took three years, we reviewed 12,000 peer reviewed papers and interviewed 88 experts from around the world. We took no money from the private sector or governments – we had no conflicts of interest.

“The most striking outcome is that we have over-stated the effectiveness of the influenza vaccine. That has had a very dampening effect on the development of new vaccines.”

“It is important to state: we support using flu vaccine in all age groups. Even among the over 65s although it is of limited benefit it is still a benefit. We surely have overstated the level of protection but it still offers some protection.”

Douglas Fleming, of the Royal College of General Practitioners’ Influenza Monitoring Unit in Birmingham, said: “No vaccines are perfect. Last year’s flu vaccine was a bad match with the circulating strains. Its effectiveness varies from year to year and with different age groups. Amongst the elderly it is widely recognised that its effectiveness decreases. Better vaccines are needed for this reason particularly. It has been over-hyped by many people.”