Quick, longer COVID-19 shutdowns most effective — but consider socio-economic cost 'trade-off': study

Shutdown measures need to be put in place early — when community transmission rates are low — and tend to be lengthy to effectively fight COVID-19, an unavoidable "trade-off" that can come with "substantial" socioeconomic costs, according to a new study by Public Health Agency of Canada researchers.

The PHAC team of scientists explored the impact of shutdown measures on COVID-19 transmission in Canada for the study "Modelling the impact of shutdowns on resurging SARS-CoV-2 transmission in Canada." It was published Wednesday in the peer-reviewed journal Royal Society Open Science.

"We understand that shutdowns have an immense socio-economic impact on individuals, families and businesses, and we wanted to develop a study that could help decision-makers develop their trade-off with the public health outcomes," said Victoria Ng, a scientist based in Guelph, Ont., and study co-author.

Researchers explored four different shutdown scenarios that considered the speed at which shutdowns have been implemented, their length, breaks in between shutdowns and targeting different sectors.

"Shutdowns were shown to largely delay the epidemic with growing cases, hospitalizations and death rates when the response is slow," the study concluded.

While "all shutdowns had some impact on the epidemic, the trade-offs are important to consider based on the local context and situation." 

Different scenarios

The PHAC team also used a data-based mathematical model that replicated how people behave across various sectors, such as at school, workplaces, also factoring in age. 

The model considered different health measures, such as social distancing and masking, but not vaccine use as the study was conducted in September, before mass vaccinations started in recent weeks.

"There isn't really a best shutdown strategy because there is always a trade-off," Ng told CBC Kitchener-Waterloo. "When we showed shutdowns where we had lower number of cases, hospitalizations and deaths in community, they always had the highest number of shutdown days, and this would have a substantial socio-economic impact on society and individual and families."

The shutdown duration explored in the report ranged from 28 to 70 days and beyond.

The effective scenario also targeted sectors such as schools, workplaces, and other non-essential and public facilities.

Repeated short shutdowns not ideal

One scenario, which considered delays between different shutdowns, suggested a lengthier shutdown with public health measures in mind will help control the infection. However, if a shorter shutdown is implemented repeatedly, for example, it is difficult to control the situation.

"That's not enough. You bring down cases, but it's not going to bring them down completely, so if you reopen, those cases will be going back up and you'll hit that threshold to shut down again," said Ng.

She said it's difficult to compare the study's results to what's happening now in Ontario because they may vary depending on each jurisdiction and its COVID-19 statistics.

She said policymakers may consider this information when exploring shutdown outcomes, but not when developing a COVID-19 safety plan.

Ng said shutdowns are effective in controlling the spread of COVID-19, but not on their own.

"There are other public health measures that can be put in place and can be enhanced because ... shutdowns are so disruptive. They should be avoided whenever possible and only used when we need to control the spread of COVID."