OBJECTIVES: We aimed at comparing the epidemiology of influenza and Respiratory syncytial virus (RSV) before and after the COVID-19 pandemic.

METHODS: Yearly population-based data for both influenza and RSV were collected from national surveillance databases over the period 2010-2023 (with the COVID-19 pandemic occurring throughout 2020/22). We looked at confirmed symptomatic cases and hospitalizations for both general and at-risk populations and used Chi-square tests to describe the evolution of outcomes pre/post COVID-19. Country scope included the US and EU-5 countries (France, Germany, Spain, Italy and the UK).

RESULTS: Analyses could not be conducted for Italy and Spain as data for 2021/23 were missing, and influenza and RSV circulation was undetectable during the 2020/21 season. Rates for influenza cases and hospitalizations for the general population in the UK during pre-COVID-19 ranged from 57.6 to 84.0 p100,000 and from 4.9 to 84.4 p100,000, respectively. Outcomes for the 2022/23 season (post COVID-19) showed a significant increase in cases and hospitalization with 69.0 p100,000 and 87.3 p100,000, respectively, (p<0.05). Comparable trends were observed in France and the US and in the elderly. Similarly, RSV hospitalizations rates for the general population ranged from 8.8 to 28.3 p100,000 in the US before COVID-19 and evolved to 51.0 p100,000 in 2022/23 (p<0.05), with similar trends observed in France, Germany and the UK.

CONCLUSIONS: Our observations support a scenario that was anticipated by health authorities, and this rebound in viral activity is likely attributable to the cessation of non-pharmaceutical interventions that were deployed during the COVID-19 pandemic such as mask-wearing. This resurgence in activity, combined with significant drops in influenza vaccine coverage rate (VCR) constitutes a significant threat to public health, and returning to pre-COVID-19 VCR should constitute a priority. As RSV vaccines will soon be available, efforts should also be focused on raising awareness and encouraging populations to get vaccinated.