The world’s most extensive COVID-19 vaccine study began on Monday with the help of 30,000 volunteers testing out the newly developed shots by the U.S. government.

The vaccine created by the National Institutes of Health and Moderna is still in the experimental phase and is not guaranteed to protect against the virus. Participants will not be allowed to know who received the vaccine and who received the placebo for researchers to test the efficacy of the vaccine. This latest study is said to be just one of the many vaccine studies scheduled to take place between the summer and fall. CNBC reports that Oxford’s COVID-19 shot study is set to begin in August while Johnson & Johnson is scheduled for September, Novavax in October, and Pfizer has plans for its own 30,000 volunteer study sometime this summer.