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Title: High infection fatality rate among elderly and risk factors associated with infection fatality rate and asymptomatic infections of COVID-19 cases in Hong Kong
Authors: Tao, J
Zhang, X
Musa, SS 
Yang, L 
He, D 
Issue Date: May-2021
Source: Frontiers in medicine, May 2021, v. 8, 678347
Abstract: Background: Since the emergence in December 2019, the COVID-19 pandemic has become one of the greatest global public health threats in history. However, asymptomatic infections have increased the challenges of providing accurate estimates for the infection fatality rate (IFR) of COVID-19. Methods: We calculated the asymptomatic case ratios based on the reported COVID-19 cases in Hong Kong where intensive testing has been conducted in close contacts and high-risk populations. We estimated the IFR using both symptomatic and asymptomatic cases as denominator. The boosted regression tree (BRT) and multivariable logistic regression models were used to identify relative contribution and effect size of the risk factors associated with the asymptomatic cases and IFRs. Results: The ratio of the asymptomatic patients in Hong Kong was higher than many other regions over the world. Imported cases had a higher asymptomatic proportion than local cases. Older age and male were associated with a higher IFR than younger age and females. Conclusion: Policymakers should consider the potential risk factors for the asymptomatic infections and IFRs by the Hong Kong surveillance data to mitigate the diseases and reduce the case mortality of COVID-19.
Keywords: Asymptomatic COVID-19 cases
Boosted regression tree
Hong Kong
Infection fatality rate
Publisher: Frontiers Research Foundation
Journal: Frontiers in medicine 
EISSN: 2296-858X
DOI: 10.3389/fmed.2021.678347
Rights: © 2021 Tao, Zhang, Musa, Yang and He. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) ( The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
The following publication Tao J, Zhang X, Musa SS, Yang L and He D (2021) High Infection Fatality Rate Among Elderly and Risk Factors Associated With Infection Fatality Rate and Asymptomatic Infections of COVID-19 Cases in Hong Kong. Front. Med. 8: 678347 is available at
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