A group of researchers, led by a prominent Indian scientist has taken a big step towards developing an universal vaccine that would protect people from every kind of flu.

"We know the exact subgroup of the immune system and we've identified the key fragments in the internal core of the virus. These should be included in a vaccine," Ajit Lalvani, the leader of the group said.

Seasonal flu kills between 2,50,000 and 5,00,000 people each year and new pandemics have the potential to take doctors by surprise. The influenza virus is constantly shifting target making seasonal vaccines useless and new ones needed each year.

"In truth, in this case it is about five years (away from a vaccine). We have the know-how, we know what needs to be in the vaccine and we can just get on and do it," said Lalvani, a professor at Imperial College, London.

Their discovery has been published in the Nature Medicine journal.

This vaccine would take a distinct approach compared with other forms of vaccination, such as the MMR jab. The new vaccine will trigger the immune system to produce antibodies that can attack an invader.

Researchers admit it is harder to develop this kind of vaccine than to provoke an antibody response. The challenge will be to get a big enough T-cell response to offer protection and a response that will last.

John Oxford of Queen Mary University of London said, "This sort of effect can't be that powerful or we'd never have pandemics. It's not going to solve all the problems of influenza, but could add to the range of vaccines. It's going to be a long journey from this sort of paper to translating it into a vaccine that works."

Sarah Gilbert, who is also trying to develop an universal flu vaccine at the Jenner Institute in Oxford, said, "Live attenuated influenza vaccines which are given by nasal spray and will be used in children in the UK from this autumn are much better at increasing the number of influenza-specific T-cells."

"But, these vaccines only work in young children who haven't yet had much exposure to influenza virus, so we need an alternative approach for adults," she added.

"The new publication contains information on the precise characteristics of the influenza-specific T-cells which were protective, and this information will be useful in monitoring the immune response to vaccination when testing novel influenza vaccines which are designed to provide protection against pandemic as well as seasonal influenza viruses," Gilbert said.