A Study to Learn How Paxlovid [Nirmatrelvir-ritonavir/PF-07321332] Works in COVID-19 Patients Who Are Elderly or Have Medical Conditions.

The purpose of this study is to learn about the effects of the study medicine called Paxlovid \[nirmatrelvir-ritonavir/PF-07321332\], for the potential treatment of COVID-19. This study will use patient health records in Ontario, to find people who were sick with COVID-19 and visited a pharmacist to be treated, anytime from December 1st, 2022, to March 31st, 2024. To be included in our study, the people must be over 18 years of age and be registered in the Ontario health system for at least one year. People were not included in our study if they have been pregnant in the past year or have serious kidney or liver disease. We will separate the people in the study into two groups: those who received treatment with Paxlovid \[nirmatrelvir-ritonavir/PF-07321332\] and those who received no treatment. We will monitor their healthcare visits or if they die for any reason, for up to 60 days after the date that they visited their pharmacist. Then we will compare participant experiences when they are taking the study medicine to when they are not. This will help us determine if the study medicine is effective.

Inclusion * Record of at least 1 nirmatrelvir-ritonavir prescription and at least 1 dispensation issued by the pharmacist (Treated Cohort only) within 5 days of prescription, identified through pharmacy billing codes * Record of at least 1 assessment for nirmatrelvir-ritonavir, without a prescription issued by the pharmacist (Untreated Cohort only), OR record of at least 1 prescription for nirmatrelvir-ritonavir without dispensation (Untreated Cohort only), identified through pharmacy billing codes Exclusion * Invalid or incomplete records (e.g., missing age, missing sex, death before index) * Record of a positive PCR test for SARS-CoV-2 between 5 and 90 days prior to the index date * Had a prescription for antivirals within 3 days prior to or on the index date