The 2025/26 flu season in Europe started earlier than the previous two seasons.[1] It is powered by the recently discovered influenza A(H3N2) subtype K virus.[1] According to the European Center for Disease Prevention and Control (ECDC), flu cases in EU countries, Norway, Iceland and Liechtenstein are appearing three to four weeks earlier than in previous years.[1] This early onset may lead to greater spread of the virus during the winter.[1] The article provides early estimates of the effectiveness of the seasonal influenza vaccine against influenza requiring medical care at the primary care level in Europe for weeks 41 to 49 of 2025. The new H3N2 subclade K variant is particularly at risk for high-risk groups.[1] The ECDC urges vaccination, although it admits that the effectiveness of this year's vaccine is questionable.[1]