CIRANO has published an update of its exploratory study to estimate the incidence of COVID-19 cases in Quebec. This update integrates the data from the third week of collection, which took place from January 27 to february 1st, 2022, with a sample of 3000 respondents representative of the Quebec population and compares them to other collection weeks.

It should be noted that this study is spread over four consecutive weeks in order to monitor the evolution of the situation. The study uses both a direct sampling strategy and an indirect sampling estimation based on the network scale-up (NSS) method. Details of the methods are available in the CIRANO 2022s-03 working paper.

Highlights: The number of adults newly infected with COVID-19 based on PCR, rapid tests, or self-diagnosis over the past 7 days is 298,311 (42,616 cases per day) based on our direct sampling estimate. Excluding self-diagnosis, we instead obtain 183,530 cases over the past seven days, or an average of 26,219 cases per day.

By the network scale-up (NSS) method, we obtain estimates consistent with the direct sampling strategy, for the total population, of 161,308 new cases for the week under consideration (23,044 cases per day) using the estimator of Habecker et al. (2015) and 181,396 cases (25,914 cases per day) with the estimator of Killworth et al.

Data collected at time 3 suggest a decrease in the incidence of COVID-19 cases compared to the previous week. This decrease in incidence is not statistically significant in the direct sampling estimate. However, the decrease is significant in the RPA-based estimates. Therefore, these results should be taken with caution. However, by generating smaller standard deviations, the RPA method provides greater precision in estimating the trend in case incidence.

This study is conducted by a team of researchers composed of David Boisclair (HEC Montréal), Roxane Borgès Da Silva (Université de Montréal and CIRANO), Vincent Boucher (Université Laval) Nathalie de Marcellis-Warin (Polytechnique Montréal and CIRANO), Pierre-Carl Michaud (HEC and CIRANO) and Ingrid Peignier (CIRANO)