A new generation of more effective flu vaccines is “urgently needed” to prevent widespread illness and death.
Scientists from the University of Minnesota in the US 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 (TIV), 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.
However, this type of vaccine is not currently recommended for children in the UK.
Dr Michael Osterholm, 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.
“We should maintain public support for present vaccines that are the best intervention available for seasonal influenza.”
The research showed that pandemic swine flu vaccine was about 69 per cent effective in people aged under 65.