Impact of COVID-19 infection control measures on influenza-related outcomes in Hong Kong.

Following the announcement of coronavirus disease 2019 (COVID-19) cases in Wuhan on 31 December 2019, government officials in Hong Kong recommended the wearing of face masks as a public infection control measure against the COVID-19 virus and curtail the impact of the concurrent influenza season. The present study evaluated the influenza-related outcomes between the influenza season 2019 and 2020 in Hong Kong as a result of these infection control measures. A Monte Carlo simulation model was designed to estimate the number of influenza cases, clinic visits, hospitalization, deaths, direct medical cost and disability-adjusted life-years (DALYs) for the season 2018-2019 and 2019-2020 in six age groups: 0-5 years, 6-11 years, 12-17 years, 18-49 years, 50-64 years and ≥65 years in Hong Kong. Model inputs were derived from public data and existing literature. The model findings showed significant reduction in influenza-related cases, clinic visits, hospitalization, and deaths in 2020 versus 2019 (p < 0.05). Influenza-related direct costs in all age-groups were significantly reduced by 56%-82% (p < 0.01) in 2020 versus 2019. DALYs were also significantly decreased by 58%-85% (p < 0.01). The direct cost and DALYs avoided in 2020 was the highest among the age group of 0-5 years with a cost-saving of USD593,763 (95%CI 590,730-596,796) per 10,000 population and a DALY reduction of 57.67 (95%CI 57.54-57.83) per 10,000 population. This study illustrated the reduction of all influenza-related outcome measures in Hong Kong as a result of the implementation of public infection control measures against COVID-19.