A retrospective study of the effects of COVID-19 Non-pharmaceutical interventions on Influenza in Canada.

The COVID-19 pandemic had a significant impact on endemic respiratory illnesses. Through behavioural changes in populations and government policy, mainly through non-pharmaceutical interventions (NPIs), Canada saw historic lows in the number of Influenza A cases from 2020 through 2022. In this study, we use historical influenza A data for Canada and three provincial jurisdictions within Canada: Ontario, Quebec and Alberta to quantify the effects of these NPIs on influenza A. We aim to see which base parameters and derived parameters of an SIR model are most affected by NPIs. We find that the effective population size is the main driver of change, and discuss how these retrospective estimates can be used for future forecasting.