MILWAUKEE (AP) — Officials say there is a critical need for blood plasma from recovered coronavirus patients in Wisconsin.

Convalescent plasma has been shown to be effective in treating the most seriously ill coronavirus patients, but the demand is far greater than the supply.

Versiti Blood Center of Wisconsin’s chief medical officer, Dr. Thomas Abshire, said the need for convalescent plasma in Wisconsin is about double the number of donors giving plasma.

Advocate Health Care transplant director Dr. Ajay Sahajpal says Wisconsin has already needed to import plasma from other states, but that might not continue as the shortage of donors continues elsewhere.