by the other. The first case had been wearing valve-equipped face masks, and sometimes none, when stepping out of his room, which allegedly led to a contamination of the corridor and the infection of a person staying in the opposite room. Yuen ascribed the transmission to the use of valve masks, which he called "selfish" by design as they did not filter the exhaled air, which he said was "not good". On 24 November, the Centre for Health Protection forbade the use of valve masks effective from the following day, and exhorted the public to refrain from using them. On 29 November 2021, a team led by Yuen succeeded in isolating the Omicron variant. On 19 January 2022, Yuen published a statement justifying the culling of 2,000 hamsters by the Hong Kong government sparking backlash from animal rights activist groups. On 23 January 2022, Yuen warned that if a recent outbreak with the Omicron variant in Kwai Chung Estate with over 100 cases failed to be contained, this could result in that outbreak to last up to three months and to have a major impact on businesses. He reiterated his earlier statements that the SARS-CoV-2 virus was there to stay, and questioned the heavy focus of the government on zero coronavirus cases; the zero-Covid policy should be considered as a means to "buy time" to increase the vaccination rate, not as a way for anti-pandemic measures to end. In relation to Chief Executive Carrie Lam having removed her mask after taking her seat at a press briefing a day earlier, Yuen assessed the risk of transmission in that situation as low but urged experts and leaders to "set an example" themselves by wearing a mask, as he himself would wear two. On 10 February 2022, Yuen suggested that, in view of insufficient resources to handle the pandemic, the infected with no or mild COVID-19 symptoms isolate at home and unvaccinated elderly, or chronic patients they live with, be moved to spaces at centres such as AsiaWorld-Expo to avoid cross-infection. In an article published in early March 2022, Yuen and his team identified Omicron variants with specific spike proteins that will give it antibody evasive properties. This finding showed how the new Omicron variant can lower the efficiency of vaccines in use. On 15 July, Yuen and his team published an article outlining the next course of action for the Hong