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Stringency of containment and closures on the growth of SARS-CoV-2 in Canada prior to accelerated vaccine roll-out.
Vickers, David M; Baral, Stefan; Mishra, Sharmistha; Kwong, Jeffrey C; Sundaram, Maria; Katz, Alan; Calzavara, Andrew; Maheu-Giroux, Mathieu; Buckeridge, David L; Williamson, Tyler.
  • Vickers DM; Centre for Health Informatics and Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
  • Baral S; Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, United States.
  • Mishra S; MAP Centre for Urban Health Solutions, St. Michael's Hospital, Unity Health Toronto, Toronto, ON, Canada; Division of Infectious Diseases, Department of Medicine, University of Toronto, Toronto, ON, Canada.
  • Kwong JC; ICES, Toronto, ON, Canada; Public Health Ontario, ON, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada; Centre for Vaccine Preventable Diseases, University of Toronto, Toronto, ON, Canada; Department of Family and Community Medicine, University of Toronto, ON, C
  • Sundaram M; ICES, Toronto, ON, Canada; Centre for Clinical Epidemiology and Population Health, Marshfield Clinic Research Institute, Marshfield, WI, USA.
  • Katz A; Departments of Community Health Sciences and Family Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
  • Calzavara A; ICES, Toronto, ON, Canada.
  • Maheu-Giroux M; Department of Epidemiology, Biostatistics, and Occupational Health, School of Population and Global Health, McGill University, Montréal, QC, Canada.
  • Buckeridge DL; Department of Epidemiology, Biostatistics, and Occupational Health, School of Population and Global Health, McGill University, Montréal, QC, Canada.
  • Williamson T; Centre for Health Informatics and Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
Int J Infect Dis ; 118: 73-82, 2022 May.
Article in English | MEDLINE | ID: covidwho-1700024
ABSTRACT

BACKGROUND:

Many studies have examined the effectiveness of non-pharmaceutical interventions (NPIs) on SARS-CoV-2 transmission worldwide. However, less attention has been devoted to understanding the limits of NPIs across the course of the pandemic and along a continuum of their stringency. In this study, we explore the relationship between the growth of SARS-CoV-2 cases and an NPI stringency index across Canada before the accelerated vaccine roll-out.

METHODS:

We conducted an ecological time-series study of daily SARS-CoV-2 case growth in Canada from February 2020 to February 2021. Our outcome was a back-projected version of the daily growth ratio in a stringency period (i.e., a 10-point range of the stringency index) relative to the last day of the previous period. We examined the trends in case growth using a linear mixed-effects model accounting for stringency period, province, and mobility in public domains.

RESULTS:

Case growth declined rapidly by 20-60% and plateaued within the first month of the first wave, irrespective of the starting values of the stringency index. When stringency periods increased, changes in case growth were not immediate and were faster in the first wave than in the second. In the first wave, the largest decreasing trends from our mixed effects model occurred in both early and late stringency periods, depending on the province, at a geometric mean index value of 30⋅1 out of 100. When compared with the first wave, the stringency periods in the second wave possessed little association with case growth.

CONCLUSIONS:

The minimal association in the first wave, and the lack thereof in the second, is compatible with the hypothesis that NPIs do not, per se, lead to a decline in case growth. Instead, the correlations we observed might be better explained by a combination of underlying behaviors of the populations in each province and the natural dynamics of SARS-CoV-2. Although there exist alternative explanations for the equivocal relationship between NPIs and case growth, the onus of providing evidence shifts to demonstrating how NPIs can consistently have flat association, despite incrementally high stringency.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: Vaccines / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study Topics: Vaccines Limits: Humans Country/Region as subject: North America Language: English Journal: Int J Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: J.ijid.2022.02.030

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Vaccines / COVID-19 Type of study: Experimental Studies / Observational study / Prognostic study Topics: Vaccines Limits: Humans Country/Region as subject: North America Language: English Journal: Int J Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: J.ijid.2022.02.030