From December 2022 to January 2023, new Coronavirus Disease 2019 (COVID-19) outbreaks emerged in almost all cities of China. It is estimated that approximately 90% of the population in China was infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within these two months. 1 Bai Y Shao Z Zhang X et al. Reproduction number of SARS-CoV-2 omicron variants, China, December 2022-January 2023. J Travel Med. 2023; 30 (taad049) Crossref Scopus (4) Google Scholar However, there are no available prophylactic agents against COVID-19 for most of the general population. During this period, the absolute predominance of SARS-CoV-2 infection resulted in the rapid development of COVID-19 related symptoms, including fever, cough, headache and so on, while similar symptoms caused by other viruses were extremely rare. Thus, this in fact provides good feasibility for analyzing which factors in daily life could help the population defend against SARS-CoV-2 infection. However, until now, there is still a lack of analysis of those people who successfully resisted SARS-CoV-2 infection and did not have obvious COVID-19 related symptoms during this period.