Dr. David Heymann, an epidemiology professor serving as a special advisor to the World Health Organization, said Sunday it’s not yet known if people who have been infected with the coronavirus develop an immunity to it.

The idea of releasing people who have been infected and recovered from the virus back into the workforce has been floated by officials as a possible next step in managing the crisis.

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“Do you have any reason to believe that once someone is infected that they then become immune? Or do you think this virus will hit in waves again and again?” CBS’s “Face the Nation” host Margaret Brennan asked Heymann.

“It's too early to say for sure,” Heymann responded. “Hopefully there will be a solid immunity that develops so that vaccines can be developed that will be effective and other means of prevention will be possible.”

Heymann said that other coronaviruses do not develop long term immunity, adding that people get infected with the coronavirus that cause common colds on a regular basis.

Asked about the possibility of lifting restrictions in place, Heymann said it “depends on the risk assessment in the country.”

“They need to understand where the majority of transmission is occurring and then they need to keep those sectors locked down most while unlocking the sectors where transmission is less important and heavy measures in place to stop transmission should it begin to increase again,” Heymann said.