[2] Tam has played a leadership role in Canada's response to public health emergencies, including SARS, H1N1, MERS, Ebola,[4][5] and COVID-19.

"[16] On 23 January, Tam was a member of the WHO committee that broadcast that it was too early to declare a public health emergency of international concern.

[18][19] On 6 April, Tam changed her recommendation to "wearing a non-medical mask, even if you have no symptoms, as an additional measure that you can take to protect others around you in situations where physical distancing is difficult to maintain" because of new data about pre-symptomatic and asymptomatic transmission.

[19] On 23 April, Tam was appointed by Justin Trudeau to a new advisory body, the COVID-19 Immunity Task Force, whose mandate he declared to be the coordination of serological surveys across the country.

[20] In February 2021, an Auditor General's report described how the Public Health Agency of Canada led by Tam failed to fully comprehend the threat posed by COVID-19 to Canadians.

[21] In particular, it was noted that the Agency "did not consider forward-looking pandemic risk" when it concluded that COVID‐19 would have a minimal impact if an outbreak were to occur in Canada.