By the end of April 2021, the United States had fully vaccinated just under a third of its popu-lation against Covid-19. Initial federal and state vaccination strategies focused on hospitals, mass-vaccination centers, and re-tail pharmacies, quickly vaccinating health care workers and residents of long-term care facilities who were at high risk for Covid-19. Dif-ficult cold-storage requirements, scarce supply, and urgency may have justified strategies that large-ly bypassed the outpatient practic-es normally responsible for most vaccinations.