There is lots of luck involved with the flu shot as well. They range from 1/3 to 2/3 effective, it depends on the year. In 2019, the vaccines were 37% effective against Influenza A and 50% against Influenza B, but the B variant was more prevalent that year so the overall effectiveness was 45%. (https://www.cdc.gov/mmwr/volumes/69/wr/mm6907a1.htm?s_cid=mm...)

We are still trying to figure out how to make effective flu vaccines.