In an ongoing study of more than 300 Covid-19 patients treated with convalescent plasma therapy in the US, researchers suggest that the treatment is safe and effective. The study, published in the American Journal of Pathology, tracked 350 severely ill Covid-19 patients admitted to the Houston Methodist's system of eight hospitals from March 28 through July 6.

"Our studies to date show the treatment is safe and, in a promising number of patients, effective," said study author James M Musser from the Houston Methodist in the US.