Prevalence and impact of SARS-CoV-2, influenza, respiratory syncytial virus (RSV) infection and respiratory illness on UK healthcare workers during winter 2023/24 (September 2023 to March 2024): SIREN cohort study

Background: During the winter, healthcare systems experience additional pressures due to increases in respiratory infections and staff absence. We aimed to determine the prevalence of respiratory viruses and impact on sickness absence in the SIREN healthcare worker (HCW) cohort during winter 2023/24. Methods: SIREN is a cohort study with linked testing, vaccination, demographic, symptoms and sick leave data. Participants undergo fortnightly multiplex PCR testing for SARS-CoV-2, influenza and RSV, regardless of symptoms. The proportion of participants who took sick leave, the total number and median of sick leave days taken was calculated, overall and stratified by viral infection and vaccination status. Logistic regression was used to estimate the association between sick leave and vaccination status. Results: A total of 5287 participants were included, 78·3% female, median age 54 years. There were 1828 infections (1161 SARS-CoV-2; 387 RSV; 280 influenza infections) among 1659 participants. Influenza and RSV peaked in December (1·2%; 1·9%), SARS-CoV-2 peaked in September and December 2023 (4·0%; 4·3%).Regardless of a known infection, 35.8% (1892/5287) took sick leave, resulting in 10,168 days (median 5 days per person; range 1–98 days). Discussion: Respiratory illness caused a substantial burden on the SIREN healthcare workforce over winter, with all three viruses contributing. Reduced number of staff at work and pressures to work through illness have implications for healthcare resilience.