Generally, historically, if the overseas panel physician doing you medical exam gives you a blanket waiver for a vaccine based on it "not being available in the country at that time", as he should have if it wasn't flu season, then the adjudicating officer won't override that waiver. As long as the vaccine assessment (DS-3025) is marked as "K-Visa applicant voluntarily completed all vaccine requirements" you should be good. The notable exception as of late has been the polio vaccine, but that is a different animal because the CDC changed the age requirements in May 2024. Many overseas medical clinics either didn't get the change notice or ignored it and incorrectly issued a blanket waiver for the vaccine "Not being age appropriate". USCIS, in those instances, has the authority to overrule the panel physician because what they did is an error in direct contravention to the CDC guidelines, and they have been issuing RFEs for applicants to get the vaccine. In the case of the flu vaccine, the blanket waiver given to you by the panel physician was correct and within guidelines at the time of your exam so I think the liklihood of it being required at the interview is extremely low.