Development of universal vaccines represents an area of ongoing, active research (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028071/ ). The goal of these vaccine approaches is to both expand the protective scope (e.g. protecting against a broader range of influenza viruses) and extend the protective duration (e.g. not needing an updated vaccination every flu season). One of the primary reasons a new flu shot is formulated every influenza season is that influenza viruses circulating in humans are constantly changing (termed ‘antigenic drift’ (read more at: https://www.cdc.gov/flu/about/viruses/change.htm ). Because our current inactivated influenza vaccines are targeted against parts of the virus that are most prone to change over time, yearly vaccination with updated flu shots ensures that you can develop protective immune responses against the most currently circulating strains possible.