Pfizer and BioNTech Announce Phase 3 Trial Data Showing High Efficacy of a Booster Dose of Their COVID-19 Vaccine First results from any randomized, controlled COVID-19 vaccine booster trial demonstrate a relative vaccine efficacy of 95.6% against disease during a period when Delta was the prevalent strainIn trial with more than 10,000 participants 16 years of age and older, COVID-19 booster was f