ABSTRACT
Introduction/Aim: Accumulating evidence indicates that an early, robust type 1 interferon (IFN) response to SARS-CoV-2 is critical for COVID-19 outcomes. Our objective was to examine the prophylactic potential of IFN treatment to limit viral transmission Methods: A cluster-randomised clinical trial was undertaken to determine effects of IFNbeta-1a treatment on SARS-CoV-2 household transmission (clinicaltrials.gov: NCT04552379). Index cases were identified from confirmed SARS-CoV-2 cases in Santiago, Chile, with 341 index cases and 831 household contacts enrolled. Households received 125 mug subcutaneous pegylated-IFNbeta-1a on days 1, 6, & 11 (172 households, 607 participants), or standard care (169 households, 565 participants). Primary outcomes included: (1) duration of viral shedding in infected cases (IC-INF), (2) transmission to treatment-eligible household contacts (EHC-ITT) at day 11. Result(s): Of 1172 individuals randomised, 53 individuals withdrew from the study (IFNbeta-1a = 35, SOC = 18). Eighty-two households (IFNbeta-1a = 36, SOC = 46) where the index case was SARS-CoV-2 negative on days 1 & 6, or with no SARS-CoV-2 negative contacts at recruitment, were excluded from exploratory analyses. Treatment with IFNbeta-1a: had no effect on duration of viral shedding in the IC-INF population (primary outcome 1), had no effect on transmission of SARS-CoV-2 at day 11 in the EHC-ITT population (primary outcome 2) but an effect was observed in a sensitivity analysis at day 6 (EHC-ITT: OR = 0.493, 95% CI = 0.256-0.949), reduced duration of hospitalisation in the IC-INF population and incidence of hospitalisation in per-protocol index cases (secondary outcome 3). In exploratory frequentist analysis, a significant effect of IFNbeta-1a treatment on SARS-CoV-2 transmission by day 11 (OR = 0.55, 95% CI = 0.36-0.99), and a Bayesian analysis identified a significant reduction in the odds of transmission (OR = -0.85, 95% credible interval = -1.59--0.16). Conclusion(s): Ring prophylaxis with IFNbeta-1a had no effect on duration of viral shedding but reduces the probability of SARS-CoV-2 transmission to uninfected, post-exposure contacts within a household.