Interim 2023/24 season influenza vaccine effectiveness in primary and secondary care in the United Kingdom

We report 2023/24 season interim influenza vaccine effectiveness for three studies, including primary care in Great Britain, hospital settings in Scotland and hospital settings in England. Adjusted vaccine effectiveness against all influenzas ranged from 63% (46 to 75%) to 65% (41 to 79%) among children aged 2-17, from 36% (20 to 49%) to 55% (43 to 65%) among adults 18-64 and from 40% (29 to 50%) to 55% (32 to 70%) among adults aged 65 and over. ### Competing Interest Statement SdeL, within his academic role is Director of the RCGP RSC. He has received grants through his University from AstraZeneca, GSK, Moderna, Sanofi, and Seqirus for vaccine related research; and been members of advisory boards for AstraZeneca, GSK, Sanofi and Seqirus. HW and CWs department has received cost-recovery payment from CSL Seqirus for analysis undertaken for regulatory review. ### Funding Statement No external funding was received; this study was funded by UK Health Security Agency, Public Health Scotland and Public Health Wales. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: UK public health agencies have permission to process patient confidential information for national surveillance of communicable diseases under: Regulation 3 of the Health Service Regulation 2002 for England, the Public Health (Scotland) Act 2008 and the NHS Scotland Act 1978 for Scotland, and the Public Health Wales National Health Service Trust (Establishment) Order 2009 for Wales. The work was reviewed by the UKHSA Research Ethics and Governance Group who confirmed the work was covered by Regulation 3 of The Health Service (Control of Patient Information) Regulations 2002, therefore specific ethical approval was not necessary. This review was also undertaken in each UK country. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Due to legal reasons supporting data is not available to share.