This is the sort of Tweet, from an eminent and influential scientist, that worries me. Resistance to flu is built upon previous immunity to similar strains - while vaccines have some effect, they are notoriously unreliable and often rely on exposure to previous strains to be most effective..
Claiming this as a victory, when it might yet have severe consequences in the future, is very short-sighted and ignores the dynamics of flu and how we evolved to live with it.