In most sectors, workplaces saw lower COVID transmission rates than in the community

Studies by Institute for Work & Health and Public Health Ontario also find layers of infection control measures adopted in vast majority of workplaces

Published: November 16, 2021

From the very start of the pandemic, measures enacted by public health authorities indicated their recognition that workplaces could be important sites of COVID-19 transmission.

Yet, such recognition was not backed up by consistent data collection to understand how workplaces compared to other sites of virus spread, said Institute for Work & Health (IWH) Senior Scientist Dr. Peter Smith in a recent webinar presentation.

As a result, he noted, it was challenging during successive waves of community spread to have an accurate picture of the role of workplaces in adding to case counts. As well, the system missed opportunities to drill down and uncover factors that may be behind COVID spread in certain workplaces and not others.

In the October 2021 IWH Speaker Series presentation, Smith shared results of two studies conducted at IWH in collaboration with Public Health Ontario using population-level data.

The two studies gave rise to findings that may surprise some, considering the heightened concern voiced in the media about work as a source of transmission during Ontario’s second and third waves.

Two studies

One finding was the widespread adoption of COVID-19 infection control measures. In a large, nationally representative series of surveys conducted by Statistics Canada, 75 per cent of respondents who continued to go to work reported four or more infection control measures at their workplaces. Another 15 per cent said their workplaces had three such measures in place.

A very small proportion—two per cent of respondents—said their workplaces had no infection control measures in place. Two per cent of approximately 11 million people (the number of Canadians estimated to have continued to go to work) is 220,000 people, and that’s still quite a lot of people, said Smith. Workers who lacked such protection (or had only one form of protection) were more likely to be new on the job, working part-time, on contract, or in sectors such as construction, utilities and agriculture/mining/quarrying/oil.

A second notable finding related to the level of transmission attributable to work. Over a year-long period between April 1, 2020, and March 31, 2021, workplace outbreaks accounted for about 12 per cent of all cases and seven per cent of all hospitalizations among working-age Ontarians. These findings are much lower than commonly perceived during some of the most anxious periods of the pandemic.

In all but three sectors, the rates of infection at workplaces were lower than rates of infection in the community, said Smith. These sectors represented about 75 to 80 per cent of the workforce that could not work from home, and included accommodation and food service, construction, education, non-food manufacturing, retail trade, transportation and warehousing and wholesale trade.

The three sectors where workplace infection rates were consistently higher than general rates were agriculture, health care and social assistance, and food manufacturing—which is consistent with media reports spotlighting the heightened risks in these sectors.

Questions to further explore

Looking at rates of transmission together with use of infection prevention measures, Smith pointed to different outcomes in industries that should theoretically have been more similar. He noted, in particular, differences in transmission rates between food manufacturing (about 14 cases per million hours worked) and other types of manufacturing (about four cases per million hours worked)—two comparable sectors that had similar levels of physical distancing practices.

This points to some of the missed opportunities for learning when it came to workplace outbreaks, said Smith. We haven't done enough in collaboration with public health to really understand why the COVID virus seems to spread in some workplace settings much more than others. It's not just about access to infection control procedures. Other characteristics of the environment must be important.

How the studies were done

The first of the studies Smith presented was based on data collected by Statistics Canada between July and September 2020, in a special supplement to the Labour Force Survey that included questions on COVID infection control measures at worksites. After Smith and his team removed answers from people who were self-employed or who worked from home, they had a sample of about 53,300 responses.

Survey participants were asked about a range of workplace practices. These included: 1) practices that allowed for physical distancing; 2) increased access to hand sanitizer or handwashing facilities; 3) enhanced cleaning protocols; and 4) access to masks, face shields, gloves, gowns or other types of personal protective equipment. Smith noted that a potentially important infection control practice—ventilation—was not asked about in the survey. That’s a reflection of the timing of the survey, which took place before the importance of ventilation was widely recognized.

The vast majority of survey respondents said their workplaces had infection prevention policies in place. These included physical distancing (84 per cent), personal protective equipment (PPE) (88 per cent), handwashing (91 per cent) and cleaning (86 per cent).

Given the heightened risks of transmissions faced by workers in health care and social assistance services, it was to be expected that this was the sector with the most prevalent use of PPE. However, in terms of physical distancing, other sectors such as manufacturing, wholesale trade, retail trade, and accommodation and food services all had more widespread use of distancing. Notably, distancing was markedly low in construction and transportation and warehousing.

Smith also noted other personal and workplace characteristics linked to low levels of PPE and infection control. For example:

  • Men, compared to women, had lower levels of all infection control practices.
  • Workers with lower levels of education had lower levels of physical distancing and less access to enhanced cleaning in their workplaces.
  • Workers with six months or less in job tenure had lower levels of all types of infection control practices.
  • Non-permanent workers had less access to PPE and less access to enhanced cleaning practices.
  • People in smaller workplaces (i.e. fewer than 20 employees) had less access to PPE.
  • Workers who had no option to work from home had less physical distancing and less access to enhanced cleaning.

Interestingly, we saw no differences between unionized and non-unionized workers, and no differences across racial/immigrant groups or across hourly wage levels, he said.

For the second study, on rates of workplace transmission in Ontario, Smith and the research team used the number of workplace outbreaks, defined by public health units in most sectors as instances when two or more cases were detected in a workplace over a 14-day period, and a link could be established between the cases. Smith noted, however, that this definition was not used uniformly across sectors, especially at the beginning of the pandemic (for example, single cases were considered outbreaks in long-term care homes and child-care settings). He also noted that public health units across the province could vary in how vigilant they were in identifying and following up on workplace outbreaks. Despite the inconsistencies, outbreak data did provide the team an opportunity to identify the types of workplace settings where the cases did occur—something not available in the absence of routine collection of work information by the health system.

The first study is published in the November issue of Statistics Canada’s Health Reports (doi:10.25318/82-003-x202101100002-eng). The second study has not yet been accepted for publication but is available online in pre-publication (doi:10.1101/2021.06.30.21259770).