In 2004, SARS patients in an open‐label study had better clinical outcomes when treated with ribavirin in combination with lopinavir‐ritonavir (400 and 100 mg, respectively) than the control group receiving only ribavirin. 227  A study in SARS patients found that viral replication could not be blocked at ribavirin concentrations achievable in human serum. 234  Nevertheless, the combination of ribavirin with IFN‐β had a synergistic effect on the inhibition of SARS‐CoV‐1 replication. The effects of PEGylated IFN together with ribavirin against SARS‐CoV‐2 are being studied in clinical trials. 87