Researchers at Harvard say COVID-19 still poses a serious threat, and stay-at-home orders and school closures may be needed intermittently until at least 2022.

They say a vaccine may still be a year away.

The Harvard team determined the lengthy timeline based on estimates of "seasonality, immunity, and cross immunity" for two prior betacoronaviruses. They also project that "recurrent wintertime outbreaks of SARS-CoV-2 (COVID-19) will probably occur after the initial, most severe pandemic wave."

See the full study here.

While federal social distancing guidelines are set to expire on May 1, Dr. Anthony Fauci says reopening the country then is "overly optimistic."

Analysis: Can Trump order states to reopen?

And the director of the CDC calls social distancing "one of the most powerful weapons" the country has against the coronavirus.