saw this old tweet from POTUS in my screenshots, it’s still stumps me ....does anybody know what this might mean?🤷‍♀️

If I remember correctly it was after his recovery from covid. When you come into contact with the virus, your body produces antibodies that remain in the blood for a long time after recovering. Thus, you have immunity to this virus forever. Your blood becomes a drug or vaccine. It is enough to separate the antibodies from the blood. Maybe, theoretically, giving the antibodies to another person will let their body know how to defend itself against the virus...