A rolling cycle of 50 days of strict lockdown measures followed by 30 days of easing of restrictions could be an “effective” approach for managing Covid-19 until there is a vaccine, research suggests.

This model would keep intensive care demand within capacity and “may allow populations and their national economies to ‘breathe’ at intervals”, according to a study published in the European Journal of Epidemiology. A continuous, three-month strategy of suppression measures, such as strict physical distancing and lockdown, would reduce new coronavirus cases to near zero in most countries, the study indicated.

There are currently no effective treatments for the disease and a widely-available vaccine is likely to be at least a year away. The principal strategy to control the disease globally has focused on measures that minimise person-to-person transmission of SARS-CoV-2 through social distancing; including isolating suspected infected individuals, shielding vulnerable groups, school closures, and lockdowns says the research.

Scientists studied three scenarios.The first scenario modelled the impact of imposing no measures. As might be expected, the number of patients requiring treatment in intensive care units (ICUs) would quickly exceed the available capacity significantly for every single country, resulting in a total of 7.8 million deaths across the 16 countries. Under this scenario, the duration of the epidemic would last nearly 200 days in the majority of the countries included.

The second scenario modelled a rolling cycle of 50-day mitigation measures followed by a 30-day relaxing. Such a strategy would be likely to reduce the R number (the number of people each infected individual goes on to infect) to 0.8 in all countries. However, it would still be insufficient to keep the number of patients requiring ICU care below the available critical care capacity. While proving effective for the first three months for all the countries, after the first relaxation, the number of patients requiring ICU care would exceed the hospital capacity and would result in 3.5 million deaths across the 16 countries. In this scenario, the pandemic would last approximately 12 months in high-income countries, and about 18 months or longer in the other settings.

The final scenario involved a rolling cycle of stricter, 50-day suppression measures followed by a 30-day relaxing. Such intermittent cycles would reduce the R number to 0.5 and keep ICU demand within national capacity in all countries. Since more individuals remain susceptible at the end of each cycle of suppression and relaxation, such an approach would result in a longer pandemic, lasting beyond 18 months in all countries. However, a significantly smaller number of people—just over 130,000 across the 16 countries modelled—would die during that period.

In comparison, the team found that after a continuous, three-month strategy of strict suppression measures, most countries would reduce new cases to near zero. Looser, mitigation strategies would require approximately 6.5 months to reach the same point. However, such prolonged lockdowns would be unsustainable in most countries due to potential knock-on impacts on economy and livelihood.

Dr. Rajiv Chowdhury, a global health epidemiologist the University of Cambridge, UK, and lead author on the paper, said: “Our models predict that dynamic cycles of 50-day suppression followed by a 30-day relaxation are effective at lowering the number of deaths significantly for all countries throughout the 18-month period.

“This intermittent combination of strict social distancing, and a relatively relaxed period, with efficient testing, case isolation, contact tracing and shielding the vulnerable, may allow populations and their national economies to ‘breathe’ at intervals—a potential that might make this solution more sustainable, especially in resource-poor regions.”


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