For the past eight years, flu shots around the world have contained a virus that was retrieved from a sick person in California in the spring of 2009, in the earliest days of the H1N1 — or swine flu — pandemic. No more. This week, the World Health Organization recommended that flu vaccine manufacturers swap out the component that is based on that virus with an updated version. It is uncommon for a flu virus to remain in the vaccine for such an extended period as the current one.
https://www.statnews.com/2016/09/30/flu-vaccine-makeover-strains/
