It appears that an influenza vaccine does not just work when it comes to influenza. A new study shows that elderly people who have been admitted to an intensive care units have less risk of dying and of suffering a blood clot or bleeding in the brain if they have been vaccinated. And this is despite the fact that they are typically older, have more chronic diseases and take more medicine then those who have not been vaccinated.
source https://www.lifetechnology.com/blogs/life-technology-news-blog/flu-vaccine-reduces-risk-of-dying-for-elderly-intensive-care-patients