In November 2021, Pfizer and the Medicines Patent Pool signed a licence agreement to facilitate affordable access of Pfizer’s oral COVID-19 antiviral treatment candidate nirmatrelvir (PF-07321332) in combination with low dose ritonavir in 95 countries.

Nirmatrelvir in combination with a low dose of ritonavir was found to reduce the risk of hospitalisation or death by 89% compared to placebo in patients treated within three days of symptom onset (primary endpoint) in an interim analysis of a Phase 2/3 trial of non-hospitalised high-risk adults with COVID-19.