Although it's not perfect (you're not totally immune), it's still effective at significantly bringing down hospital visits & mortality rates.

This is especially true for those with weak immune systems. As for a source, see the "Effectiveness" section https://www.health.nsw.gov.au/Infectious/Influenza/Pages/you...

Quote "One European study in 2008 found a 66% vaccine efficacy (VE) against confirmed influenza for children aged 9 months to 3 years, while a Japanese study of children aged 6 months to 6 years found VE against influenza A ranged from 42% to 69% depending on the vaccine match"

Another source with an effectiveness section has similar numbers: https://www.cdc.gov/flu/prevent/misconceptions.htm

That's very far away from your "flu vaccine is terrible ineffective" statement.