Flu: the disease that won’t go away

Technologist: Why is it so hard to contain seasonal flu?

AB Osterhaus: At least three to four different strains of the influenza virus circulate each year, and as seasons change they travel from the northern to the southern hemisphere. Throughout their journey, the strains face defence mechanisms in the human population, so they have to mutate to “survive”. In other words, the antibodies we all carry against the flu provide the constantly evolving disease with an escape strategy.

T. Why do we have to create a new vaccine every year?

A.O. Each year has a different flu-strain profile: circulating strains change constantly through mutation and other genetic mechanisms.

T. Why does it work better some years than others?

A.O. Although the chosen vaccine strains usually match the circulating viruses well, it occurs that we pick a wrong strain for the vaccine. This is what happened last year, when the vaccine was less effective than usual. An important point here is that vaccine production takes about six months, leaving time for viruses to mutate away from the profile we’ve based the vaccine on. I don’t think this will happen often in the future, as the selection of the relevant strains keeps getting better along with improvements in the global surveillance program.

T. Why is it so difficult to predict and prevent flu epidemics?

A.O. Nature is still smarter than us! We’re getting better at predicting seasonal flu strains, but when it comes to the more serious types of influenza – the ones that may be contracted from birds – we’re still looking for ways to rapidly identify the avian viruses that hold the greatest pandemic potential. That requires working with potentially dangerous viruses in the lab.

T. What would it take to make the perfect flu vaccine?

A.O. To find a universal flu vaccine, we may have to turn our attention from antibodies to additional arms of the immune system. A striking point could be T-cells, also known as “killer cells” or “helper cells”. Stimulating T-cells to beat the flu is very complicated, but a realistic possibility. Although I doubt we’ll ever reach the Holy Grail – that one-shot-for-the-rest-of-your life vaccine – I’m sure more universal flu vaccines will eventually come along.