Many diseases are stable/not subject to mutation - polio, measles, smallpox, etc. Because of this the vaccination efficacy rates are high ( 90% range). Flu, like COVID, is subject to constant mutation. Efficacy rates have maxxed at 60% & usually far lower (15-40%).
https://fortune.com/well/article/rfk-jr-cdc-cancels-flu-vaccine-campaign-amid-surge/