Researchers say they are now on the verge of developing a flu vaccine that will provide life-long protection against any type of flu, BBC News reports.

Two separate teams of US researchers have found positive results with the vaccine that focuses on the stable part of the flu virus. The current flu vaccine has to be administered every year since it focuses on the mutating part of the virus.

The vaccine has shown promising results when tested on animals. Studies are now needed to confirm that the vaccine will work in case of humans.

The work is published in Science journal and Nature Medicine.

According to BBC News, Prof John Oxford, a flu expert at the University of London said,

"This is a leap forward compared to anything done recently. They have good animal data, not just in mice but in ferrets and monkeys too. And they've done it with the bird flu virus H5N1."

"It's a very good stepping stone. Ultimately, the hope is to get a vaccine that will cover a pandemic virus."

Experts said people should continue to receive their annual vaccination as it is still the best way to protect oneself against infection.

According to BBC News, Prof Sarah Gilbert, Professor of Vaccinology at University of Oxford, said: "This is an exciting development, but the new vaccines now need to be tested in clinical trials to see how well they work in humans.

"This will be the next stage of research, which will take several years. So we are still some way from having better flu vaccines for humans."