An international team is working on a vaccine that would protect against every type of flu and fight off all major strains of influenza — from the routine winter flu to virulent new strains of bird flu — and it claims that the vaccine could be available within a few years.

In fact, the scientists believe they have solved the problem of designing a “one fits all” jab using a new two-step approach to immunisation.

According to them, early safety trials of flu vaccine have already started and it could be tested on human patients as early as 2013, the British media reported.

Though the jab for humans is at an early stage of development, the scientists have tested it successfully on mice, ferrets and monkeys whose immune systems were “primed” with a “base” of influenza DNA.

In monkeys, they added a “booster” consisting of regular seasonal flu vaccine which increased and broadened its immunity. The vaccine’s effectiveness improved each year until recipients would be immune to the flu.

Scientists wrote in the ‘Science’ journal, “We are excited by these results. The prime-boost approach opens a new door to vaccinations for influenza that would be similar to vaccination against diseases as hepatitis, where we vaccinate early in life and then boost immunity through occasional, additional inoculations in adulthood.”

“We may be able to begin efficacy trials of a broadly protective flu vaccine in three to five years,” Dr Gary Nabel, the study leader from the US National Institute of Allergy and Infectious Diseases in Bethesda, said.

The scientists also measured how well the prime-boost vaccine protected mice and ferrets against deadly levels of flu virus.

Three weeks after receiving the boost, 20 mice were exposed to high levels of 1934 flu virus and 80 per cent survived. When mice were given only the “prime” or “boost” elements alone, or a sham vaccine, all died.

Similar results were seen in ferrets, which are good predictors of flu vaccine effectiveness in humans.

Experts have more or less welcomed the research.

Prof John Oxford, Britain’s leading flu expert and a virologist at St Bart’s and Royal London hospitals, said: .

“This is a new and interesting approach and they are a much respected group. I would take this very seriously. They seem to have identified a universal or general antibody that attacks many different types of virus.

“This is something that we have been after for a long time but the next stage is crucial. Many new vaccines fall at the human trial stage.”

Prof Hugh Pennington of Aberdeen University said:

“It is an exciting and attractive approach. We really do desperately need something along these lines. It is a nice idea but the proof will be in the pudding and seeing whether it works in humans.”