http://www.sciencemag.org/news/2020/12/innovative-universal-flu-vaccine-shows-promises-it-first-clinical-test

Seasonal flu vaccines induce antibodies against the “head” (slate) of the influenza surface protein hemagglutinin, but a new universal vaccine triggers antibodies (fragments of them shown in gray) that bind to the stalk (light blue) portion.

For epidemiologists, the COVID-19 pandemic has greatly intensified their longstanding nightmare about another virus: the emergence of a new and deadly strain of flu. A universal flu vaccine, effective against any strain of the influenza virus that can infect humans, could protect us from this peril, but progress has been slow. A novel concept for such a universal flu vaccine has now passed its first test in a small clinical trial, its developers report today in Nature Medicine.