Fifty days of strict lockdowns followed by 30 days where measures are eased could be an effective strategy for reducing Covid-19 deaths while ensuring some level of economic protection, scientists claim.
In an EU-backed study published on Wednesday, a cohort of researchers from nine countries simulated how various lockdown strategies would impact the spread of the coronavirus.
There have been almost 5 million cases of Covid-19 confirmed globally, with over 300,000 deaths from the virus worldwide, according to data compiled by Johns Hopkins University.
Many governments have imposed some form of lockdown to mitigate transmission of the virus. But policymakers around the world are now calculating ways to gradually lift those measures as the pandemic weighs heavily on economic activity.
Scientists suggested in the new report that an alternative, more effective approach to indefinite or milder lockdowns could be alternating stricter measures with intervals of relaxed social distancing. Effective testing, contact tracing and isolation strategies, as well as efforts to shield society's most vulnerable, would be consistently kept in place.
They modeled several different scenarios on 16 countries, including Australia, Mexico, Belgium, South Africa and Nigeria.
In the first scenario, no mitigation or social-distancing measures were imposed. In every single country, this led to the number of patients requiring treatment in intensive care units (ICUs) quickly and significantly exceeding available capacity. Ultimately, this would result in 7.8 million deaths across the countries included in the analysis, researchers said, and the duration of the epidemic would be almost 200 days in the majority of those nations.
The second scenario modeled a rolling cycle of 50-day "mitigation measures" followed by a 30-day period where those measures were relaxed. Analysts defined mitigation measures as strategies that gradually reduced the number of new infections, such as social distancing, hygiene rules, isolating individuals with the virus, school closures and restricting large public events. These measures did not include a total lockdown.
This scenario was likely to reduce the R number — the reproduction rate of the virus — to 0.8 in all countries, the study showed. However, while it proved effective for the first three months, after the first relaxation period scientists found the number of patients requiring ICU care would exceed hospital capacities. This would lead to 3.5 million deaths across the 16 countries used in the simulation, with the pandemic lasting around 12 months in high income countries and at least 18 months in other nations.
Researchers also modeled a third scenario, which involved a rolling cycle of stricter "suppression measures" for 50 days followed by a 30-day relaxation period. Suppression measures were defined as those that led to a faster reduction in the number of new infections, achieved by applying strict lockdown measures on top of other mitigation measures.
In the third, most stringent scenario, the R number would be reduced to 0.5 and keep ICU demand within national capacity across all countries, scientists concluded. As more people would remain susceptible to catching the virus at the end of each cycle, however, the pandemic would be prolonged and last for more than 18 months in all countries.
But the Covid-19 death toll during the pandemic would be significantly reduced in this scenario, with just over 130,000 deaths expected across the 16 countries included the analysis.
Researchers noted that individual countries would need to define for themselves how long the durations of the intervals would last to suit their domestic needs and facilities.
A continuous, three-month strategy of strict suppression measures would be the fastest way to end the pandemic, with most countries able to reduce new cases to near zero in this scenario, scientists said.
Meanwhile, if looser mitigation strategies were continuously applied, it would take just over six months for new cases to fall close to zero.
Rajiv Chowdhury, a global health epidemiologist at the University of Cambridge and the report's lead author, said the third scenario — rotating strict suppression measures with relaxation periods — may allow populations to "breathe" at intervals.
"That might make this solution more sustainable, especially in resource-poor regions," he said.
Oscar Franco, director of the Institute of Social and Preventive Medicine at the University of Bern in Switzerland, added that the research provided a strategic option for countries to better control Covid-19.
"There's no simple answer to the question of which strategy to choose," he said. "Countries — particularly low-income countries — will have to weigh up the dilemma of preventing Covid-19 related deaths and public health system failure with the long-term economic collapse and hardship."
The IMF has warned that the world is on course for the deepest recession since the 1930s thanks to the coronavirus pandemic, predicting that the global economy will contract by 3% this year.