aStanley Ho Centre for Emerging Infectious Diseases

bThe JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin

cSpecial Preventive Programme, Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region Government

dDepartment of Medicine and Geriatrics, Princess Margaret Hospital, Hong Kong, China.

Correspondence to Denise P.C. Chan, Stanley Ho Centre for Emerging Infectious Diseases, Postgraduate Education Centre, Prince of Wales Hospital, Shatin, Hong Kong, China. Tel: +852 2252 8812; fax: +852 2635 4977; e-mail: [email protected]

Received 21 May, 2022

Accepted 27 May, 2022