1. Centre for Health Protection, Department of Health, Hong Kong SAR. Vaccination schemes at a glance 2017 [accessed 2017 Sep 14]. http://www.chp.gov.hk/en/features/18870.html.
2. Centre for Health Protection, Department of Health, Hong Kong SAR. Statistics on 2017/18 vaccination programmes/schemes [accessed 2018 Mar 9]. https://www.chp.gov.hk/en/features/26734.html.
3. World Health Organization. Recommended composition of influenza virus vaccines for use in the 2017-2018 northern hemisphere influenza season. [accessed 2018 Jul 15]. http://www.who.int/influenza/vaccines/virus/recommendations/2017_18_north/en/.
4. Centre for Health Protection, Department of Health, Hong Kong SAR. Flu express. [accessed 2018 Mar 9]. https://www.chp.gov.hk/en/resources/29/304.html.