A new generation of more effective flu vaccines is “urgently needed” to prevent widespread illness and death, it was claimed.

Scientists who analysed 40 years of data concluded that current vaccines offered inadequate protection against both seasonal influenza outbreaks and serious pandemics.

Evidence for their effectiveness in older individuals was also lacking, said the researchers who pooled the results of 31 studies published over four decades.

Overall, the most widely used seasonal flu vaccine, known as trivalent inactivated vaccine, was only 59 per cent effective in healthy adults.

A newer kind of nasal spray vaccine containing a weakened “live” virus, LAIV (Live Attenuated Influenza Vaccine) was shown to prevent influenza in 83 per cent of children aged seven or younger.

Michael Osterholm, from the University of Minnesota in the US, one of the lead authors of the study published in the journal The Lancet Infectious Diseases, said: “Evidence for consistent high-level protection is elusive for the present generation of vaccines, especially in individuals at risk of medical complications or those aged 65 years or older.

“The ongoing health burden caused by seasonal influenza and the potential global effect of a severe pandemic suggests an urgent need for a new generation of more highly effective and cross-protective vaccines that can be manufactured rapidly.

“In the meantime, we should maintain public support for present vaccines that are the best intervention available for seasonal influenza.”

The scientists wrote: “This amount of protection is not adequate for a pandemic setting. The difference between 69 per cent effectiveness and 90 per cent effectiveness (or greater) will have a major public health effect in any pandemic that causes serious morbidity (illness) or increased mortality.”