WASHINGTON, April 15 (Xinhua) -- Prolonged or intermittent social distancing may be necessary into 2022 to prevent future COVID-19 seasonal outbreaks, according to a new study from Harvard researchers published on Tuesday.

The researchers, led by Stephen Kissler, research fellow at Harvard T.H. Chan School of Public Health, used estimates of seasonality, immunity, and cross-immunity for two betacoronaviruses from time series data from the United States, to inform a model of COVID-19 transmission.

Recurrent wintertime outbreaks of COVID-19 "will probably occur after the initial, most severe pandemic wave," researchers wrote on Science magazine, adding that without a vaccine or other interventions, "prolonged or intermittent social distancing may be necessary into 2022."

Noting that "a key metric for the success of social distancing is whether critical care capacities are exceeded," the study said that "additional interventions, including expanded critical care capacity and an effective therapeutic, would improve the success of intermittent distancing and hasten the acquisition of herd immunity."

Longitudinal serological studies are urgently needed to determine the extent and duration of immunity to the virus, the researchers said.

Even in the event of apparent elimination, COVID-19 surveillance should be maintained since a resurgence in contagion could be possible as late as 2024, according to the study.  ■