Scientists are investigating the use of blood plasma from recovering COVID-19 patients as a tool to prevent infection in others. Blood plasma, which is the material that’s left after red and white blood cells have been removed, is rich in antibodies and may help those who have been exposed to the coronavirus who are at high risk of infection.

According to NPR, the technique follows the same principle as a rabies shot. If you’ve been bitten by a potentially rabid animal, the shot can prevent infection. A study is now being conducted, sponsored by Johns Hopkins University, to determine if using the plasma from recovered patients also can prevent high risk people from becoming infected by COVID-19.

Dr. Shmuel Shoham, who is directing the study, said he hopes to recruit 500 patients and has set up sites in Baltimore, Dallas, Arizona and several locations in California.

Convalescent plasma has been used for more than 100 years to help people survive life threatening infections, according to Medical News Today. On March 28, Houston Methodist Hospital in Texas became the first academic center in America to treat critically ill COVID-19 patients with convalescent plasma.

Shoham said he is also involved in a second study that will investigate whether plasma can prevent serious illness in people who are infected, but not sick. He said that if infusing plasma into patients can help prevent infections as well as assist those who are ill, the double whammy may help control the coronavirus even without a vaccine.

“That would give people a lot of confidence, I think, to go back to school, go back to work,” he told NPR, “because if someone gets sick it’s not a tragedy — because we can protect them and protect those around them.