Just for a starter antibody treatment from survivors, monoclonal antibodies manufactured after analyzing and reproducing those antibodies. Because you are not an expert let me explain, antibodies are these really amazing things produced by the human body that aid in fighting disease. They do not in themselves kill an invader, however they make them sticky so they agglutinate or for the layman clump together. The result is that the foot soldiers of the immune army(the white blood cells in this instance lymphocytes) can engulf and kill them more easily and efficiently.
You may have noticed the testing for immunity to Covid19, which is now coming on line is called the Covid AG test AG standing for agglutinazation. It is important that the antibody titer(ratio of antibodies in the blood is high) to insure immunity as this titer drops you become less immune, but the body never forgets once it has made antibodies it will make them again more rapidly which is why vaccines are effective against the majority of virae.. Therefore you may get the disease again if enough time passes but severity will be less unless you have become immuno compromised. In some cases boosters are given to insure continued immunity.
Oh and the antibodies are virus specific, meaning the body produces specific antibodies for a specific virus, if the virus has a major mutation the antibodies would not necessarily be effective against a major mutation, then again a major mutation could make the virus inert.