Article in New Yorker about how C19 spreads in the human body. It also provides an interesting background on immunization dating to 1100 when Chinese doctors were successful with live virus immunization.
Based on the article, it would be interesting to have Dr. Fauci's view on if this should be trialed in US to see if it provides protection greater than the fatality rate.
"The Indian practitioners of tika had likely learned it from Arabic physicians, who had learned it from the Chinese. As early as 1100, medical healers in China had realized that those who survived smallpox did not catch the illness again (survivors of the disease were enlisted to take care of new victims), and inferred that the exposure of the body to an illness protected it from future instances of that illness. Chinese doctors would grind smallpox scabs into a powder and insufflate it into a child’s nostril with a long silver pipe."