Epidemiology of virologically confirmed RSV, influenza and COVID-19 in adults in England, 2023-2024: Primary Care Observational Study of Acute Respiratory Infection (ObservatARI).

OBJECTIVES: To describe the positivity, clinical presentation and predictors of respiratory syncytial virus (RSV) in adult primary care patients compared to influenza and SARS-CoV-2, prior to the introduction of RSV vaccines. METHODS: We analyzed data from primary care patients aged ≥40 years with an acute respiratory infection. Between 02/10/2023 and 10/04/2024 virology swabs were tested by the UK Health Security Agency for RSV, influenza A and B, and SARS-CoV-2. Percent positivity with 95% confidence intervals (CIs) were estimated. Multivariable logistic regression identified predictors of infection. Clinical presentations were described and compared. RESULTS: Among 6,161 individuals tested, influenza A had the highest positivity (3.25%, 95% CI: 2.83-3.72), followed by SARS-CoV-2 (2.30%, 95% CI: 1.96-2.71), RSV (2.26%, 95% CI: 1.91-2.66), and influenza B (0.28%, 95% CI: 0.17-0.44). RSV positivity was higher in people aged 60-74 compared to those aged 40-49. RSV cases presented with ILI less often than COVID or influenza A cases. CONCLUSIONS: During the 2023/24 winter season in England, medically-attended RSV presented a significant disease burden, with a positivity comparable to SARS-CoV-2 and approximately 70% of influenza. Given well-established vaccination programmes for influenza and COVID-19, these findings demonstrate an opportunity to introduce an RSV vaccination program for adults.