Fisman was part of the Ontario COVID-19 Science Advisory Table until his resignation in August 2021, alleging that "grim" COVID-19 projections for the fall of 2021 were being withheld.[14][15][16] In June 2020, he supported the use of masks by school children in Canada, at a time when the Hospital for Sick Kids did not consider them necessary.[17] He has supported wider recognition of airborne spread as the primary transmission mechanism for SARS-CoV-2.[18][19]
Fisman was criticized by the Ontario government for acting as paid consultant for the Elementary Teachers' Federation of Ontario (ETFO), during which he provided evidence that did not support the governments reopening efforts.[20][21][22] This occurred while he was serving on the Science Advisory Table, whose director stated that his work with the ETFO "didn't violate any policies".[20] A Toronto City Councilor, viewed his efforts as pushing for government accountability.[20] Conversely, Dr. Euzebiusz Jamrozik from the bioethics research centre at the University of Oxford noted that this relationship should have been disclosed as a potential conflict of interest.[21] Fisman noted his relationship as an advisor to the ETFO on a January 26, 2021 disclosure form to the Science Advisory Table, but indicated that this was not related to COVID-19.[23]
On April 25, 2022, the Canadian Medical Association Journal published a study co-authored by Fisman that claimed unvaccinated Canadians pose a risk to the vaccinated population.[24] Based on modelling scenarios developed by the authors, the study suggested that individuals who have received two or three doses of a COVID-19 vaccine are more likely to be infected with SARS-CoV-2 by an unvaccinated person - conversely, unvaccinated people experienced "decreased attack rates" as a result of mixing with vaccinated people.[25] Fisman and his co-authors concluded that the "equity and justice" for vaccinated individuals should be weighed alongside those of the unvaccinated population when developing vaccination policies in preparation for future seasonal outbreaks and variants.[26] However, Fisman acknowledged that the study's model does not reflect the real world or other factors that should be taken into account when implementing public health measures, such as public anger and politics.[27]
^David, Fisman (2021-02-10). "Declaration of Interest"(PDF). Ontario COVID-19 Science Advisory Table. Archived(PDF) from the original on 2022-04-30. Retrieved 2022-04-30.
^ abDavid, Fisman (January 26, 2021). "Declaration of Interest"(PDF). Ontario COVID-19 Science Advisory Table. Archived(PDF) from the original on 2021-03-17. Retrieved January 24, 2022.