The NCGM’s Center Hospital and several other hospitals in Tokyo, Osaka and Nagoya have been asking recovered COVID-19 patients to donate their plasma samples if an initial blood test confirms the presence of high levels of antibodies, The Japan Times reported on Sunday.

The Center Hospital has tested around 700 recovered patients and gathered plasma from nearly 200 of them, said Satoshi Kutsuna, chief physician at the NCGM’s Disease Control and Prevention Center.

"This will likely not be effective for patients with severe symptoms," Kutsuna said, adding that  "we've been gathering reports that it's effective to use it on patients in the early stages after the onset of symptoms, so I think it’s important to inject it" even earlier rather than later.

Takeda co-founded the CoVIg-19 Plasma Alliance in April last year to help develop a potential plasma-derived therapy called hyperimmune intravenous immunoglobulin medicine.

However, the alliance last month ended their one-year collaboration after a clinical trial of nearly 600 adult patients in the US and 10 other countries failed to reach its targets.