[1] World Health Organization. Novel coronavirus (COVID-19) situation. https://covid19.who.int/. [2021-8-19].https://covid19.who.int/
[2] Cherian S, Potdar V, Jadhav S, Yadav P, Gupta N, Das M, et al. Convergent evolution of SARS-CoV-2 spike mutations, L452R, E484Q and P681R, in the second wave of COVID-19 in Maharashtra, India. bioRxiv 2021. http://dx.doi.org/10.1101/2021.04.22.440932.http://dx.doi.org/10.1101/2021.04.22.440932
[3] Xia F, Yang XP, Cheke RA, Xiao YN. Quantifying competitive advantages of mutant strains in a population involving importation and mass vaccination rollout. Infect Dis Model 2021;6:988 − 96. http://dx.doi.org/10.1016/j.idm.2021.08.001CrossRef
[4] CNTV. 7.05 million people in Guangzhou have been vaccinated with SARS-CoV-2 vaccines, and the vaccination rate of the target population has reached 63.4%. https://baijiahao.baidu.com/s?id=1700366214344124056&wfr=spider&for=pc. [2021-5-21]. (In Chinese). https://baijiahao.baidu.com/s?id=1700366214344124056&wfr=spider&for=pc
[5] Eight O’clock News. From 0 to 346 cases, the epidemic situation in Yangzhou is the epitome of China’s second and third tier cities against delta strain. https://baijiahao.baidu.com/s?id=1707576508728914568&wfr=spider&for=pc. [2021-8-9]. (In Chinese).  https://baijiahao.baidu.com/s?id=1707576508728914568&wfr=spider&for=pc
[6] Li XN, Huang Y, Wang W, Jing QL, Zhang CH, Qin PZ, et al. Effectiveness of inactivated SARS-CoV-2 vaccines against the Delta variant infection in Guangzhou: a test-negative case-control real-world study. Emerg Microbes Infect 2021;10(1):1751 − 9. http://dx.doi.org/10.1080/22221751.2021.1969291CrossRef
[7] Jara A, Undurraga EA, González C, Paredes F, Fontecilla T, Jara G, et al. Effectiveness of an inactivated SARS-CoV-2 vaccine in Chile. N Engl J Med 2021;385(10):875 − 84. http://dx.doi.org/10.1056/NEJMoa2107715CrossRef
[8] Li T, Liu Y, Li M, Qian XN, Dai SY. Mask or no mask for COVID-19: a public health and market study. PLoS One 2020;15(8):e0237691. http://dx.doi.org/10.1371/journal.pone.0237691CrossRef