Yes, there have been some trials in avian flu at least, and a few attempts in original SARS and MERS, with success. The problem here is the mediocre quality of

Yes, there have been some trials in avian flu at least, and a few attempts in original SARS and MERS, with success. The problem here is the mediocre quality of evidence. Mostly limited sizes, but also lacking randomization. Also rabies, tetanus and hepatitis B and C sera are available. Those have high quality evidence for working.