Seattle Children’s Hospital is planning to begin serving inpatients up to and including age 21, the hospital’s chief executive officer said Tuesday. The executive said the move was intended to give other hospitals more space to treat adults who test positive for the novel coronavirus.

The hospital primarily serves children from birth until teen-hood; patients transition to adult providers when they’re aged 18 to 21. Young adults usually aren’t first-time patients at this hospital, officials said.

Seattle Children’s will also begin accepting children from nearby hospitals that choose to shut down or shrink pediatric units to make room for adults with the virus, said the hospital’s chief executive officer, Jeff Sperring, during an online Q&A with media Tuesday morning. Some of Seattle’s hospitals were already at or near capacity before the coronavirus outbreak and are urgently seeking emergency medical staff and supplies — and looking for ways to add hospital beds for sick patients.

Seattle Children’s has tested 660 children so far, four of whom had a positive result. One child was placed in a special isolation unit, but all of the children have since returned home and are recovering. The hospital has 20 beds in its isolation unit but intends to expand that, officials said.

Research hints that children are susceptible to the coronavirus infection but are mostly spared the disease’s worst effects. Older adults are most likely to experience serious symptoms, research suggests.

Seattle Children’s test results are generally in line with existing studies, Sperring said.

“[It] so far has been reassuring in that we are not seeing the caseloads in children at the same level” seen in adults, he said. But there’s a caveat: “The only children that were screened were symptomatic,” he said, so the hospital’s case numbers shed little light on how often children are infected but not ill. Researchers also know little about how well children transmit the virus to others.

Four staff out of 166 who have received tests have also tested positive, officials said.   The hospital is screening patients when they drive up to the emergency department, and sending those who meet certain criteria for coronavirus testing to a special waiting area. The hospital is also using other techniques to keep staff and patients safe, such as using telemedicine and limiting visitors to two parents or caregivers per patient.