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. 2024 Jan 12:3:1248847.
doi: 10.3389/fepid.2023.1248847. eCollection 2023.

The descriptive epidemiology of pre-omicron SARS-CoV-2 breakthrough infections and severe outcomes in Manitoba, Canada

Souradet Y Shaw  1   2 , Jason Kindrachuk  2 , Lyle McKinnon  2 , Jeffery C S Biegun  3 , Jocelyn N Reimer  4 , Carla Loeppky  5 , Yichun Joy Wei  5 , Jared Bullard  6 , Paul Van Caeseele  6 , Derek R Stein  6
Affiliations

The descriptive epidemiology of pre-omicron SARS-CoV-2 breakthrough infections and severe outcomes in Manitoba, Canada

Souradet Y Shaw et al. Front Epidemiol. .

Abstract

Introduction: Vaccination plays a key role in curbing severe outcomes resulting from COVID-19 disease. With the Omicron variant and the relaxing of public health protections breakthrough infections are increasingly common, and certain groups remain at higher risk for severe outcomes from breakthrough infections. We analysed population-based public health data from Manitoba, Canada to understand characteristics of those experiencing breakthrough infections and severe outcomes from breakthrough infections. Data from previous pandemic stages can provide valuable information regarding severe outcomes associated with breakthrough infection in the Omicron and future phases.

Methods: Positive SARS-CoV-2 PCR tests from Cadham Provincial Laboratory were linked to case information from the population-based Public Health Information Management System. A retrospective design was used with time-to-event analyses to examine severe outcomes among those experiencing breakthrough infection.

Results: Breakthrough cases were more likely to have 2 + chronic conditions, compared to age-, sex-, and time-period matched unvaccinated cases (24% vs. 17%), with hypertension (30%), diabetes (17%), and asthma (14%) being the most prevalent chronic conditions amongst breakthrough cases. Severe outcomes resulting from breakthrough infection was associated with age and chronic conditions, with those with 2 + chronic conditions at higher risk of severe outcomes (adjusted hazard ratio: 3.6, 95% confidence intervals: 2.0-6.4). Risk of severe outcomes varied by age group, with those 70 + years at over 13 times the risk of severe outcomes (95% CI: 4.5-39.8), compared to those 18-29 years of age.

Discussion: Our results demonstrate the impact of chronic conditions on the likelihood of, and severity of outcomes from breakthrough infections. These findings underscore the importance of vaccination programs prioritizing vulnerable populations.

Keywords: COVID-19; breakthrough infection; chronic conditions; severe outcomes; vaccination.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) LM, JK declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Figures

Figure 1
Figure 1
Spider plot of chronic conditions prevalence (%), by number of chronic conditions (one, two, three, four plus), fully-vaccinated adults (18 + years) experiencing SARS-CoV-2 breakthrough infections in Manitoba, January 1–November 30, 2021 (N = 3,803)*.
Figure 2
Figure 2
Weekly summary of all reported COVID-19 cases, by breakthrough and chronic disease status, Manitoba (January 1, 2021–November 30, 2021)*. *Note different y-axes based on chronic disease status.
See this image and copyright information in PMC

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