A big step for vaccine trials

The first Phase 3 clinical trial of a coronavirus vaccine in the United States began Monday.

The investigational vaccine was developed by the biotechnology company Moderna and the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.

The trial is expected to enroll about 30,000 adult volunteers and evaluate the safety of the Moderna/NIH vaccine and whether it can prevent symptomatic Covid-19 after two doses, among other outcomes.

Results from a Phase 1 trial of the vaccine published earlier this month in The New England Journal of Medicine found it induced immune responses in all of the volunteers and was generally safe. It elicited mild side effects, including fatigue, chills, headache, muscle pain and pain at the injection site.

A Phase 1 study includes a smaller group of people and focuses on whether a vaccine is safe and elicits an immune response. In Phase 2, the study is expanded and the vaccine is given to people who have characteristics -- such as age and physical health -- similar to those for whom the new vaccine is intended. In Phase 3, the vaccine is given to thousands of people and tested for efficacy and again for safety.

This isn’t the only study to watch, though. It's one of 25 Covid-19 vaccines in clinical trials around the world, according to the World Health Organization.

Later on Monday, the first volunteers were dosed in another large-scale study of a Covid-19 vaccine developed by Pfizer and BioNTech.