Quantifying Contact Patterns in Response to COVID-19 Public Health Measures in Canada

Abstract

Background: A variety of public health measures have been implemented during the COVID-19 pandemic in Canada to reduce contact between individuals. Objective: The objective of this study was to construct contact patterns to evaluate the degree to which social contacts rebounded to normal levels, as well as direct public health efforts toward age- and location-specific settings. Design: Four population-based cross-sectional surveys. Setting: Canada. Participants: Members of a paid panel representative of Canadian adults by age, gender, official language, and region of residence. Methods: Respondents provided information about the age and setting for each direct contact made in a 24-hour period. Contact matrices were constructed and contacts for those under the age of 18 years imputed. The next generation matrix approach was used to estimate the reproduction number (Rt) for each survey. Respondents with children estimated the number of contacts their children made in school and extracurricular settings. Results: Estimated Rt values were 0.49 (95% CI: 0.29-0.69) for May, 0.48 (95% CI: 0.29-0.68) for July, 1.06 (95% CI: 0.63-1.52) for September, and 0.81 (0.47-1.17) for December. The highest proportion of reported contacts occurred within the home (51.3% in May), in other locations (49.2% in July) and at work (66.3% and 65.4% in September and December). Respondents with children reported an average of 22.7 (95% CI: 21.1-24.3) (September) and 19.0 (95% CI 17.7-20.4) (December) contacts at school per day per child in attendance. Conclusion: The skewed distribution of reported contacts toward workplace settings in September and December combined with the number of reported school-related contacts suggest that these settings represent important opportunities for transmission emphasizing the need to ensure infection control procedures in both workplaces and schools.

Modelling the impact of shutdowns on resurging SARS-CoV-2 transmission in Canada

“…This is because the second shutdown has not been as stringent as the initial one and was enacted much later when transmission levels were higher [ 1 , 2 ], thus, despite many provinces have been placed in some form of shutdown for at least a few months and for a longer period than in spring 2020, our cases per capita continue to rise to record levels [ 1 , 24 ]. Additionally, it has been bolstered by declining compliance to personal physical distancing [ 20 – 23 ].…”

“…To avoid future shutdowns, alternative public health measures should be enhanced during the delay in the epidemic afforded by the closures [ 5 , 7 ]. The precise shutdown strategy will vary depending on the community and household structures, population demographics, background transmission level and human behaviour in adhering to public health measures (which is changing over time and hard to plan for) [ 20 ]. The optimal shutdown strategy will also depend on the goal, whether it is to eliminate transmission in the population, to temporarily regain control, to buy time to ramp up other measures, to avoid overwhelming healthcare systems, to minimize the impact on the economy, communities, families and individuals or a combination of these objectives.…”

“…Personal physical distancing was also introduced in three phases with changes in contact rate and compliance from 16 March to 7 September 2020: 30% contact rate reduction with 100% compliance when outside of the household during the initial shutdown in phase 1 (15 March to 10 May) reflecting precautions Canadians were taking during the initial shutdown [ 19 ], compliance remained at 100% but contact rates were reduced to 80% when outside the household to reflect the gradual lifting of closures but continued adherence to physical distancing in phase 2 (11 May to 30 June) [ 20 , 21 ], contact rates were reduced to only 55% with compliance shifting by age group in phase 3 (1 July 2020 to model end): 0–4 (33%), 5–9 (33%), 11–14 (33%), 15–19 (33%), adult1 (50%), adult2 (75%), adult3 (85%), senior1 (90%), senior2 (95%), elderly (95%) [ 20 , 22 ]. Changes to contact rate reduction and compliance were estimated from Canadian survey data on behavioural variations to physical distancing over time [ 20 – 23 ] and the observed changes in COVID-19 cases by age groups over time [ 24 ]. In the baseline scenario, we assume everything reopens on 8 September 2020; which in reality is not the case as a large proportion of Canadians continue to telework [ 17 ] and subsequent shutdowns have occurred [ 1 , 2 ].…”

The impact of the initial public health response to COVID-19 on swine health surveillance in Ontario

“…Early surveys that were investigating social contact patterns among people in response to COVID-19 public health measures in Canada indicated high average compliance with public health measures and high average reductions in human contacts in May 2020 in Ontario. In contrast, later surveys showed an increase in human contacts in September and December 2020 in part because some public health restrictions were lifted [ 25 , 26 ]. However, to what extent the results of these surveys could be directly extrapolated to the population stratum involved in swine production is unknown.…”

Quantifying contact patterns: development and characteristics of the British Columbia COVID-19 population mixing patterns survey (BC-Mix)

“…Recent studies similar to the BC-Mix have assessed social contact patterns relevant to the spread and control of COVID-19 in different countries (7)(8)(9)(10)(11)(12)34,35) many of which have adapted features of the POLYMOD project (14). The 2020 Belgian CoMix survey ( 7) is an online longitudinal survey that closely monitors changes in social mixing behaviours among a sample of Belgian adults (aged 18 years and above).…”