[bun_at_work]

Thanks for the share. From the link:

> Why do I need a flu vaccine every year? A flu vaccine is needed every season for two reasons. First, a person’s immune protection from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, flu vaccines may be updated from one season to the next to protect against the viruses that research suggests may be most common during the upcoming flu season. For the best protection, everyone 6 months and older should get vaccinated annually.

[dragontamer]

Yeah, you're not wrong, but neither am I. Both effects happen. The flu has unusually short immunity in humans: most diseases have an immunity that lasts longer than that.

A big worry about COVID19 was the length of immunity. As a novel disease, no one knew how long human immunity would last. Fortunately, it seems to be for a long time (more than 8 months, which is the length of time these studies have been going). As such, we know COVID19 immunity is "longer than the flu", already.