Background
Influenza activity in the UK started early during the winter 2022–23 season, with most surveillance systems reporting high levels of hospitalisation, intensive care unit influenza admission and GP influenza-like illness (ILI) consultation rates. Laboratory confirmed positivity rates were comparable to those seen pre-pandemic, between the end of November 2022 and the end of January 2023, exceeding 25 % as they did during the 2019–2020 season [1], [2]. Annual vaccination against influenza is

Methods
VE against hospitalised virologically-confirmed influenza was estimated using a test-negative case-control design (TND), with the study population consisting of patients with signs/symptoms of respiratory infection, aged ≥ 18y hospitalised with an acute lower respiratory tract disease (aLRTD) between 1st October 2022 and 31st March 2023, in North Bristol and University Hospitals Bristol and Weston NHS Trusts [AvonCAP: ISRCTN17354061]. Study eligible patients were identified from the medical

Results
During the study period, 2,972 adult aLRTD hospitalisations occurred in Bristol, UK and were eligible for this analysis. Among 196 (6.6 %) who tested influenza positive, 189 were influenza A virus subtypes and 7 were influenza B. Among the study sample, 47 % of influenza-positive patients (cases) had received a seasonal influenza vaccine, compared with 63 % of influenza-negative patients (controls). The characteristics of cases and controls are listed in Table 1.The overall adjusted VE against

Discussion
In this analysis, we consider the effectiveness of seasonal influenza vaccination during the 2022–2023 season when the incidence of flu cases surpassed the levels observed in the COVID-19 pandemic influenza seasons (2020–21, 2021–22). Our findings suggest that the influenza vaccine programme in the UK provided substantial protection, reducing the risk of hospitalised virologically-confirmed influenza by 56 % among all adults, mainly against circulating influenza A viruses and more specifically