Scientists find that when flu reinfects, the immune system responds not just to the infecting strain, but also to all the strains it encountered in past
A new strategy for keeping one jump ahead of seasonal flu could improve vaccine effectiveness, scientists believe.
Research has shown that vaccines can be developed to pre-empt future dominant flu strains without risking the health of the public.
Scientists learned that, when a person catches flu, the immune system responds not only to the infecting strain but all those that have preceded it in the past.
This means it may be possible to gamble on tackling a new emerging strain without losing protection against others already in circulation.
A major problem with the seasonal flu vaccine is that by the time it becomes available, the virus has often moved on and mutated into a different form. As a result, the vaccine’s effectiveness is reduced.
Judy Fonville, one of the authors of the research from Cambridge University, said: “It’s a real challenge. The WHO [World Health Organisation] selects a strain of flu using the best information available but is faced with the possibility that the virus will evolve before the flu system.”
Flu strains are constantly changing and keeping up with them is a continual battle.
Flu strains are constantly changing and keeping up with them is a challenge
Immune reactions in ferrets − which mirror the human response to flu − are used to infer which strains are currently circulating, so that the vaccine can be tweaked to counter them.
The new discovery suggests it might be possible to update vaccines in advance to mount a pre-emptive strike against novel strains before they begin to spread.
Sam Wilks, another member of the Cambridge University team, said: “Crucially, when the vaccine strain is updated pre-emptively, we see that it still stimulates better protection against future viruses, yet this comes at no cost to the protection generated against currently-circulating ones.”
Derek Smith, also from Cambridge University, said: “The beauty of this approach is that it would not require any change to the current manufacturing process.
From the point that the new strain has been selected through to an individual receiving their shot, the steps will be exactly the same.
The only difference would be greater protection for the recipient.”
The research, reported in the journal Science, involvedmodelling the antibody response to seasonal flu using computer software.
Scientists tracked the responses of individuals over six years of exposure to flu infection and vaccination, uncovering distinct immune profiles.
A key finding was a phenomenon the researchers termed ‘back boost’ − the way the immune system recalls responses to all the flu strains a person has encountered in the past.
Each year seasonal influenza causes between three and five million cases of severe illness around the world and up to 500,000 deaths.
The team is now combining the research with other work on predicting the way the flu virus is likely to evolve.