A Phase 2 clinical trial evaluating various additional COVID-19 booster shots has begun enrolling adult participants in the United States. The trial aims to understand if different vaccine regimens—prototype and variant vaccines alone and in combinations—can broaden immune responses in adults who already have received a primary vaccination series and a first booster shot. The study, known as the COVID-19 Variant Immunologic Landscape (COVAIL) trial, is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
