A Study to Learn About a Study Medicine Called Ibuzatrelvir in Adult and Adolescent Patients With COVID-19 Who Are Not Hospitalized But Are at Risk For Severe Disease

EPIC-Peds: A Study to Learn About the Study Medicine Called PF-07321332 (Nirmatrelvir)/Ritonavir in Patients Under 18 Years of Age With COVID-19 That Are Not Hospitalized But Are at Risk for Severe Disease

A Study to Learn About Variant-Adapted COVID-19 RNA Vaccine Candidate(s) in Healthy Children

A Study to Learn About The COVID-19 (Study) Vaccine (Called COMIRNATY) in People That Are Less Than 21 Years Old.

A Study to Learn About Effects of Living With COVID-19 and the Use of the Medicines Nirmatrelvir-Ritonavir in Treating COVID-19.