Joint analysis of vaccination effectiveness and antiviral drug effectiveness for COVID-19: a causal inference approach

ObjectivesThis study aims to estimate the causal effects of oral antivirals and vaccinations in prevention against all-cause mortality and progression to severe COVID-19 in an integrative setting with both antivirals and vaccinations considered as interventions.MethodsWe identified hospitalized adult patients (i.e., aged 18 or above) in Hong Kong with confirmed SARS-CoV-2 infection between March 16th, 2022 and December 31st, 2022. An inverse probability weighted (IPW) Andersen-Gill model with time-dependent predictors was used to address immortal time bias and produce causal estimates for the protection effects of oral antivirals and vaccinations against severe COVID-19.ResultsGiven prescription is made within five days of confirmed infection, nirmatrelvir–ritonavir is more effective in providing protection against all-cause mortality and development into severe COVID-19 than molnupiravir. There was no significant difference between CoronaVac and Comirnaty in the effectiveness of reducing all-cause mortality and progression to severe COVID-19.ConclusionsThe use of oral antivirals and vaccinations causes lower risks of all-cause mortality and progression to severe COVID-19 for hospitalized SARS-CoV-2 patients.