LONDON – The latest tranche of data from an array of large-scale COVID-19 studies running in the U.K. provides real-world evidence that vaccines have a dramatic effect in preventing hospitalization and death, but that there are a very small number of vaccine failures. The data cover 3,842 people who received a vaccine and subsequently were admitted to the hospital between Dec. 8, 2020, when the national vaccination rollout began, and the data cutoff of April 10, 2021.