A vaccine against COVID-19 developed by the US biotech firm Moderna will enter the third and final stage of its clinical trial in July with 30,000 participants, the firm said Thursday.

This stage allows scientists to observe, using a large healthy population, whether the vaccine is more effective than a placebo at preventing COVID-19 and also whether it can prevent infection with the coronavirus that causes the disease.

The framework for the study was approved by the Food and Drug Administration (FDA) and is being conducted in collaboration with the US National Institutes for Health (NIH).

Moderna’s vaccine effort is a global frontrunner, alongside a vaccine being developed by the University of Oxford with AstraZeneca, which has also launched a large scale trial on 10,000 volunteers and expects results by September.