Early COVID‐19 and Severity of Subsequent Omicron Infection in Ontario Canada

Influenza and Other Respiratory Viruses 2026 Open access

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Authors: Caroline Kassee, Altynay Shigayeva, Christopher Kandel, Lubna Farooqi, Zoë Zhong, Anne‐Claude Gingras, Brenda L. Coleman, Lois Gilbert, Wayne L. Gold, Maria Major, Tony Mazzulli, Samira Mubareka
+5 more Srinivas Rao Valluri, Catherine Martin, Moe Hein Kyaw, John M. McLaughlin, Allison McGeer
DOI: 10.1111/irv.70197
Cited by: 0
References: 7

Abstract

We evaluated whether having early COVID-19 reduced the severity of subsequent Omicron infection, assessing activities of daily living (ADL), healthcare utilization and illness duration. Comparisons were made between persons with (1) early COVID-19-compatible illness with a negative test, (2) early lab-confirmed SARS-CoV-2 14-26 months and (3) early lab-confirmed SAR-CoV-2 > 26 months before Omicron infection. Among 261 patients with laboratory-confirmed Omicron, 177 (68%) had COVID-19 in 2020, a median of 793 days (IQR, 659-902) prior to Omicron infection. Compared to no early COVID-19, COVID-19 14-26 months, but not > 26 months, before was associated with reduced impact on ADL during first Omicron infection (OR 0.52, 95% CI 0.29-0.93).

Fields of Study & Subjects

SARS-CoV-2 and COVID-19 Research COVID-19 Clinical Research Studies COVID-19 epidemiological studies

Publication details

Journal / source
Influenza and Other Respiratory Viruses
Volume
20
Issue
1
Pages
e70197–e70197
Publication date
1 January 2026
Language
EN