LONDON (Reuters) - An international team of scientists has found it may be possible to make seasonal flu vaccines more effective by using an idea known as "back boost" and pre-empting flu virus evolution.
In a study published on Thursday in the journal Science, the University of Cambridge-led team said their finding should enable people to be immunized against future likely flu strains as well as ones currently circulating.
"Rather than trying to play catch-up, it's better to anticipate and prepare for the likely next step of influenza evolution," said Sam Wilks, one of the study's lead researchers.
Flu is a notoriously tricky virus to beat, since there are so many different strains circulating at any one time in both humans and animals, and each one mutates rapidly.
Yet vaccine makers need to produce around 350 million flu shot doses each year, and to do so they need to know which strains to put in the vaccine months in advance of the flu season -- during which time circulating viruses may well mutate and evolve again.
According to the World Health Organization (WHO), seasonal flu causes 3 to 5 million cases of severe illness each year worldwide and up to 500,000 deaths, as well as significant economic impact. Immunization policies vary by country, but vaccines are often recommended for people at risk of complications, including pregnant women and the elderly.
WHO scientists meet each February to select which strain to use for the coming year's vaccine, but always face the risk that the virus will mutate before the flu season even begins.
To try to overcome this problem, the researchers used immunological data to map immune system activity.
Using a new computer-based method they created so-called "antibody landscapes" showing in detail how the immune system responds to pathogens like flu that evolve and re-infect us.
Analyzing these, the scientists found that when flu re-infects, the immune system responds not just to the infecting strain, but also to all the strains it has encountered in the past -- a phenomenon the researchers termed "back-boost".
This suggests it makes more sense to pre-emptively vaccinate against likely future flu strains than to use a strain already circulating in the human population, the scientists said.
"Crucially, when the vaccine strain is updated pre-emptively ... it still stimulates better protection against future viruses -- yet this comes at no cost to the protection generated against currently circulating ones," said Wilks.
Reporting by Kate Kelland; Editing by Catherine Evans