Despite the lack of HLA-specific associations, we observed an epidemiologically meaningful correlation: individuals experiencing side effects following influenza vaccination were more than three times (OR = 3.094, CI = 2.73 – 3.50, p = 2 ×10−16) as likely to report side effects from the COVID-19 vaccine, after controlling with HLA-A*03:01. The gene discussed is HLA-A; the disease is influenza.