Did Working From Home Lower COVID-19 Risk? A July 2020 Case-Control Study

From March 2020 on, employers tried to cut workplace spread of the virus that causes COVID-19 by closing sites and offering telework — working remotely without commuting. Yet little was known about whether teleworking actually lowered a person's risk of infection. A CDC study published in MMWR looked for an answer.

How the study worked

Researchers compared symptomatic adults who had their first SARS-CoV-2 PCR test at one of 11 outpatient testing and health care centers in the IVY Network — in California, Colorado, Maryland, Massachusetts, Minnesota, North Carolina, Ohio, Tennessee, Utah and Washington — during July 1–29, 2020.

• Case-patients tested positive; control-participants tested negative.
• Participants were interviewed by phone 14–23 days after testing, in English or one of five other languages, about their work, telework status, close contacts and community activities in the 2 weeks before they fell ill.
• After excluding people who weren't symptomatic, had been tested before, or didn't answer the telework question, the final sample was 314 people: 153 case-patients and 161 controls.

What they found

People with COVID-19 were less likely to have been teleworking. Among the 248 employed participants who reported their telework status:

• Case-patients were more likely to have gone exclusively to an office or school in the 2 weeks before illness (adjusted odds ratio 1.8).
• The link held (adjusted odds ratio 2.1) among the 175 people working outside critical infrastructure jobs (health care, factories, corrections and education).
• Three-quarters of case-patients and about two-thirds of controls worked outside critical infrastructure.

Who got to telework was not random. People who teleworked were more likely to be non-Hispanic White, to have a college degree, to have health insurance and to earn $75,000 or more. In other words, non-White workers and those earning less had less chance to work from home — and similar gaps have been seen in industries where telework isn't possible.

Other activities mostly didn't differ. Teleworkers and on-site workers were equally likely to shop, visit salons, gyms, restaurants or bars and coffee shops, or use public transit. One exception: those who went to work or school regularly were more likely to attend church or religious gatherings (11% versus 3%). Teleworkers were more likely to report close contact with someone known to have COVID-19.

Both groups teleworked more than the national estimate at the time: about 26% of U.S. adults were teleworking because of COVID-19 in July 2020.

Limitations

• Participants may differ from people who declined or weren't eligible, so the results may not represent the whole U.S. population.
• The original matching of cases to controls could not be kept, though the analysis accounted for that.
• Types of telework, and whether employers had specific remote-work policies, weren't measured; the question didn't separate work from school (only eight participants were students).
• People tested at outpatient centers may not represent those with serious illness, and some negative results could reflect other respiratory viruses or limits of PCR testing.

What the authors recommend

Offering and encouraging telework where possible is an important way to reduce SARS-CoV-2 transmission, and businesses should promote alternative work arrangements to protect workers and communities. Where telework isn't possible — in critical infrastructure and elsewhere — employers should keep strengthening worker safety:

• a COVID-19 preparedness and response plan;
• social distancing and masks;
• personal protective equipment;
• daily health checks;
• hand hygiene, cleaning and disinfection;
• policies that protect employees and the community.

Sources

• Fisher KA, Olson SM, Tenforde MW, et al. "Telework Before Illness Onset Among Symptomatic Adults Aged ≥18 Years With and Without COVID-19 in 11 Outpatient Health Care Facilities — United States, July 2020," MMWR Vol. 69, No. 44, CDC; a work of the United States government in the public domain.