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Prediction of Upcoming Global Infection Burden of Influenza Seasons after Relaxation of Public Health and Social Measures for COVID-19 Pandemic
Posted: 22 Mar 2022
More...Abstract
Background: Various public health and social measures (PHSMs) have been implemented globally since early 2020 to mitigate the COVID-19 pandemic, and these measures also affected the transmission dynamics of directly transmitted respiratory viruses including influenza viruses. As a consequence, population immunity to influenza might have declined during the pandemic period. We assessed the impact of COVID-19 PHSMs on the transmissibility of influenza viruses, and predict the upcoming seasonal influenza epidemics globally.
Methods: We used surveillance data on influenza virus activity for 10 different locations/ countries across the globe during 2017-2021. We first assessed the impact of PHSMs on influenza by evaluating the reduction in community activity, transmissibility and attack rate. Then we implemented a data-driven simulation based mechanistic predictive model framework to predict potential future influenza seasons. We evaluated the potential impact of upcoming influenza epidemics in terms of fold rise in peak magnitude and epidemic size comparing the baseline activity in previous years (pre-COVID-19 pandemic). We also assessed the potential impact of enhanced influenza vaccination programs in these locations.
Findings: We estimated a maximum of 17% to 41% reduction in transmissibility and 8% to 25% reduction in influenza attack rate in the 2019-20 influenza season by the COVID-19 PHSMs in the studied locations/ countries. We estimated 20% to 70% increase in the population susceptibility for influenza, which may lead to a maximum 3-6 fold rise in peak magnitude and 2-3 fold rise in epidemic size for upcoming 2022 summer influenza season across locations if there is a complete relaxation of COVID-19 PHSMs in April 2022, with a significantly higher fold rise in Singapore and Taiwan among the locations studied. The predictions for upcoming 2022-23 winter seasons are comparable with slightly smaller fold rises compared to summer seasons in the tropical and subtropical locations. The infection burden and peak timing of upcoming influenza seasons vary with the timing and level of relaxation of COVID-19 PHSMs and could be mitigated by enhanced influenza vaccination programs.
Interpretation: Our results suggest the potential for substantial increases in infection burden for upcoming influenza seasons across the globe. Strengthening influenza vaccination programs are the best preventive measure to reduce the impact of influenza virus infections in the community.
Funding Information: This project was supported by the Health and Medical Research Fund (project no. 21200352); a commissioned grant from the Health and Medical Research Fund from the Government of the Hong Kong Special Administrative Region; the Research Grants Council of the Hong Kong Special Administrative Region, China (project No. T11-712/19N); AIR@InnoHK administered by Innovation and Technology Commission, European Research Council (grant no. 804744); the Grand Challenges ICODA pilot initiative, delivered by Health Data Research UK and funded by the Bill & Melinda Gates Foundation and the Minderoo Foundation; and Basic Science Research Program through the National Research Foundation of Korea by the Ministry of Education (NRF604 2020R1I1A3066471).
Declaration of Interests: BJC received honoraria from AstraZeneca, Fosun Pharma, GSK, Moderna, Pfizer, Roche, and Sanofi. The authors report no other potential conflicts of interest.
Suggested Citation: Suggested Citation