Abstract
Interferon (IFN) has been highlighted in several randomized controlled trials as an attractive therapeutic candidate based plausible mode of action, suppressed response in severe COVID-19, and inhibition of SARS-CoV-2 replication. This study investigated the efficacy and safety of IFN in patients with COVID-19 according to clinical severity. Randomized controlled trials evaluating the efficacy and safety of IFN (systemic or inhaled IFN-α, -β, and -λ) treatment in adult patients with COVID-19 were identified by systematically searching electronic databases until January 2023. Risk of bias were assessed using the Cochrane risk of bias tool, meta-analysis, and certainty of evidence grading were followed for the systematic review. We included 11 trials comprising 6,124 patients. Compared with exclusive standard care or placebo, IFN therapy did not provide significant clinical benefits for mortality at day 28 (pooled risk ratio [RR] = 0.86, 95% confidence interval [CI]: 0.62-1.18, 9 studies, low-certainty evidence) and progression to mechanical ventilation (pooled RR = 1.08, 95% CI: 0.81-1.43, 6 studies, low-certainty evidence) in patients with COVID-19. IFN therapy resulted in significantly increased hospital discharge on day 14 relative to the control arm (pooled RR = 1.29, 95% CI: 1.04-1.59). These results were inconsistent compared to other comparable outcomes such as recovery at day 14 and time to clinical improvement. The IFN-treated arm was as safe as the control arm, regardless of clinical severity (pooled RR = 0.87, 95% CI: 0.64-1.19, 9 studies, low-certainty evidence). In conclusion, IFN therapy was safe but did not demonstrate favorable outcomes for major clinical indices in patients with COVID-19, particularly those with higher than moderate severity. IFN therapy was not associated with worsening outcomes in patients with severe COVID-19. Future clinical trials should evaluate the clinical efficacy of IFN therapy in patients with mild COVID-19 or at an earlier stage. Trial registration: The protocol for this review was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number CRD42022301413.