Perhaps? Languages and common vernacular evolve in surprising ways. The use of 'shot' was originally meant to indicate that it is given via injection; however

Perhaps? Languages and common vernacular evolve in surprising ways. The use of 'shot' was originally meant to indicate that it is given via injection; however the word 'vaccine' may have become less common because rapid mutations result in new flu vaccine versions twice a year, and vaccination only gives a limited time resistance. It would make sense this would leads to a less formal vernacular. Since orally administered flu vaccines are in clinical trials, we might get to see vernacular evolve to accommodate them soon. All that said, "flu shot" is a common name for influenza vaccines. There is no requirement that a vaccine be highly effective or impart a long-term resistance. Rather, vaccines which are not safe and measurably effective are not desirable and thus tend to not be made available.