Strain selection and evolution of the virus
While some vaccines provide lifelong protection with one or a few doses – like measles, mumps and polio -, the flu requires a new shot every year. And in some years, the flu shot is hardly effective at all. Why is the flu vaccine different from so many other vaccines? A look at the evolution of the flu virus can explain the challenges of the strain selection process.
By Derek Smith, University of Cambridge, UK
