Per ChatGPT:
Short answer — very profitable for many sellers (especially retail pharmacies and big manufacturers), but how profitable varies a lot by who you ask, which vaccine type is used, and the payer mix (Medicare/insurer vs. cash/no-insurance)… flu shots are generally profitable for many actors: pharmacies, large clinic operators, and vaccine manufacturers all typically find flu vaccination programs to be a positive contributor to margins. Pharmacies often report higher relative margins on shots than on regular prescription retail business.