LONDON (Reuters) - A seasonal flu vaccine that would be the first in the world to fight all types of the virus is to be tested in a two-year clinical trial involving more than 2,000 patients by researchers in Oxford.

The so-called universal vaccine was developed by Oxford University’s Jenner Institute and Vaccitech, a spin-out biotech company founded by Jenner scientists.

Current flu vaccines have to be changed each year to match strains of virus circulating at the time and they do not always protect people that well, especially older patients with weak immune systems.

The new vaccine works by using proteins found in the core of the virus rather than those on its surface. Surface proteins stick out like pins from the virus and change all the time, while those in the core are stable.

Significantly, the new vaccine works by stimulating the immune system to boost virus-killing T-cells, instead of antibodies. Previous research has shown such T-cells can help fight more than one type of flu virus.

Researchers hope the new vaccine will provide better and longer-lasting protection when used alongside the regular seasonal flu shot.

“We’re hoping it will last two to three years - maybe even four years - but we really don’t know until we do the trials,” Vaccitech Chief Executive Tom Evans told Reuters.

The new vaccine has already been tested for safety in earlier trials. Now it is advancing into mid-stage Phase IIb testing, which will see the recruitment of at least 500 British subjects this season. The remainder will be recruited during the 2018/9 flu season.

It is the first time a universal flu vaccine has progressed beyond Phase I clinical testing.

Assuming it is successful in Phase IIb, the new shot will still have to go into much bigger and expensive final-stage testing and Evans said the plan would be to bring in a partner at this stage of development.

“We would look for a better-capitalised company to take this into final Phase III tests,” he said.

Leading manufacturers of seasonal flu vaccines include Sanofi, GlaxoSmithKline and CSL’s Seqirus, which includes the old Novartis flu vaccine business.