Effectiveness of Sotrovimab and Molnupiravir in community settings in England across the Omicron BA.1 and BA.2 sublineages: emulated target trials using the OpenSAFELY platform

Background The effectiveness of COVID-19 monoclonal antibody and antiviral therapies against severe COVID-19 outcomes is unclear. Initial benefit was shown in unvaccinated patients and before the Omicron variant emerged. We used the OpenSAFELY platform to emulate target trials to estimate the effectiveness of sotrovimab or molnupiravir, versus no treatment. Methods With the approval of NHS England, we derived population-based cohorts of non-hospitalised high-risk individuals in England testing positive for SARS-CoV-2 during periods of dominance of the BA.1 (16/12/2021-10/02/2022) and BA.2 (11/02/2022-21/05/2022) Omicron sublineages. We used the clone-censor-weight approach to estimate the effect of treatment with sotrovimab or molnupiravir initiated within 5 days after positive test versus no treatment. Hazard ratios (HR) for COVID-19 hospitalisation or death within 28 days were estimated using weighted Cox models. Results Of the 35,856 [BA.1 period] and 39,192 [BA.2 period] patients, 1,830 [BA.1] and 1,242 [BA.2] were treated with molnupiravir and 2,244 [BA.1] and 4,164 [BA.2] with sotrovimab. The estimated HRs for molnupiravir versus untreated were 1.00 (95%CI: 0.81;1.22) [BA.1] and 1.22 (0.96;1.56) [BA.2]; corresponding HRs for sotrovimab versus untreated were 0.76 (0.66;0.89) [BA.1] and 0.92 (0.79;1.06) [BA.2]. Interpretation Compared with no treatment, sotrovimab was associated with reduced risk of adverse outcomes after COVID-19 in the BA.1 period, but there was weaker evidence of benefit in the BA2 period. Molnupiravir was not associated with reduced risk in either period. Funding UKRI, Wellcome Trust, MRC, NIHR and HDRUK.