On Saturday the U.S. Food and Drug Administration issued an emergency use authorization (EUA) for the third vaccine for the prevention of COVID-19. The EUA allows the Janssen (company of Johnson & Johnson) COVID-19 vaccine to be distributed in the U.S for use in individuals 18 years of age and older.
The Johnson & Johnson vaccine offers a few advantages over the Pfizer and Moderna mRNA-based vaccines. The Johnson & Johnson vaccine does not require extreme low temperature storage, and it is effective in one dose vs. the two doses required by the Pfizer and Moderna vaccines. However, the Johnson & Johnson vaccine appears to be less effective overall at preventing COVID-19.