**5. Conclusions**

In conclusion, patients who receive influenza vaccination have a significantly lower risk of developing pneumonia, especially for the elderly (aged ≥ 65). The preventative effects against pneumonia depend on consecutive years of vaccination.

**Author Contributions:** Conceptualization: Y.-H.T., L.-T.Y., C.-H.C., and C.-B.Y. Validation: S.-F.Y. and C.-B.Y. Formal analysis: H.-W.Y., Y.-T.Y., and Y.-H.W. Writing—Original draft preparation: Y.-H.T., C.-H.C., M.-C.C., and C.-B.Y. Writing—Review and editing: Y.-H.T., L.-T.Y., C.-H.C., and C.-B.Y.

**Funding:** This research received no external funding.

**Acknowledgments:** This study was partly based on data from the NHIRD provided by the NHI Administration, Ministry of Health and Welfare, and managed by the National Health Research Institutes (registration number: NHIRD-104-148). The interpretation and conclusions contained herein do not represent those of the NHI Administration, Ministry of Health and Welfare, or National Health Research Institutes. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest.
