Johnson and Johnson (J&J) yesterday became the fourth drugmaker to begin a large-scale phase 3 trial of a COVID-19 vaccine candidate — and it will be the largest late-stage trial of a COVID-19 vaccine to date.

The ENSEMBLE trial will test the safety and efficacy of a single dose of Ad26.COV2.S vs. a placebo for preventing COVID-19 in 60,000 volunteers across eight countries.

The global study is being carried out in collaboration with HHS’ Biomedical Advanced Research and Development Authority and the NIH’s National Institute for Allergy and Infectious Diseases.