Weekly projections of the transmission of the Omicron variant for Ontario, and Canada

Lamps COVID-19 working group, One Health Modelling Network for Emerging Infections

On November 26, 2021, the World Health Organization (WHO) declared Omicron as a variant of concern (VOC). In late December 2021, COVID-19 cases in Ontario resurged only 4 weeks after the Omicron variant was first identified in South Africa. Testing capacity rapidly became overwhelmed in Ontario and other provinces. The government of Ontario announced a targeted testing strategy in which only individuals working or living in high-risk settings (hospitals, shelters, long-term care and group homes, correctional facilities, etc.) would be eligible for PCR testing if symptomatic [1]. Consequently, criteria for reporting cases changed as well, leading to an underreporting of total case counts. Symptomatic individuals who are no longer eligible for PCR testing are advised to self-test and isolate for five or ten days, respectively, for vaccinated and unvaccinated individuals.

This report aims to project the estimated total cases (including cases unreported due to the new testing strategy) and severe outcomes in Ontario and Canada, based on the most updated data.

Projections for Canada	Projections for Ontario
Daily reported COVID case: Confirmed (dot) vs Projected (line)	Daily reported COVID case: Confirmed (dot) vs Projected (line)
The estimated daily total (reported and unreported) Omicron cases	The estimated daily total (reported and unreported) Omicron cases
Number of hospitalized cases: Confirmed (dot) vs Projected (line)	Number of hospitalized cases: Confirmed (dot) vs Projected (line)
Number of ICU cases: Confirmed (dot) vs Projected (line)	Number of ICU cases: Confirmed (dot) vs Projected (line)
Number of deaths: Confirmed (dot) vs Projected (line)	Number of deaths: Confirmed (dot) vs Projected (line)

Notes:

1. Data resource for confirmed cases: https://health-infobase.canada.ca/covid-19/epidemiological-summary-covid-19-cases.html
2. Data resource for hospitalization cases: https://ourworldindata.org/grapher/current-covid-patients-hospital?country=~CAN
3. Data resource for ICU cases: https://ourworldindata.org/grapher/current-covid-patients-icu?country=~CAN
4. The line represents the median of 1000 simulations based on the 1000 best-fits using data up to the latest week, and the shaded area represents the 95% confidence interval of projections.

References:

1. Government of Ontario. Updated Eligibility for PCR Testing and Case and Contact Management Guidance in Ontario. 2021 [cited 2022 February 16, 2022]; Available from:  https://news.ontario.ca/en/backgrounder/1001387/updated-eligibility-for-pcr-testing-and-case-and-contact-management-guidance-in-ontario.
2. Aruffo, E., Tan, Y., Liu, Y., Ogden, N., Akingbola, S., Collier, S., Zhu, H.* (2022). Special report to Public Health Agency of Canada on “Projections of the transmission of the Omicron variant for Toronto, Ontario, and Canada using surveillance data following the recent changes in testing policies”. In “COVID-19: PHAC Modeling Group Report”, Feb. 21, 2022.
3. Newcomb, K., et al., Iterative data-driven forecasting of the transmission and management of SARS-CoV-2/COVID-19 using social interventions at the county-level. Sci. Rep., 2022. 12(1): p. 1-19.