[3] During the outbreak of avian influenza virus H5N1 in 1997 in Hong Kong, Yuen was the first to report in The Lancet about the unusual clinical severity and high mortality of infected patients, which could be identified by the in-house molecular test at his laboratory.

[5] During the global outbreak of severe acute respiratory syndrome (SARS) in 2003, he led his team in the discovery of SARS-CoV-1,[6] and subsequently traced its genetic origins to wild bats.

[9] He was an early advocate of wearing masks even by healthy individuals, citing asymptomatic cases and a large number of virus strands in saliva of an infected person.

[11] Yuen caused controversy when he and co-author David Lung published an op-ed article titled "The pandemic originated from Wuhan and the lessons from 17 years ago have been forgotten."

[21] 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.

[23] 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.

[25] 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.

[26][27] 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.

His team commented on the fact that Covid-19 cannot be cleared completely, and the government should shift their priority from lowering cases to boosting vaccination rates to achieve hybrid-immunity.

The vaccine has gained the approval of the Chinese National Medical Products administration and is projected to manufacture 200 million doses by Wantai BioPharm.