Per the FDA, the available safety data to support the EUA includes an analysis of 43,783 participants enrolled in an ongoing randomized, placebo-controlled study conducted in South Africa, South America, Mexico, and the US.
• 21,895 of the participants received the J&J vaccine.
• 21,888 of them received a placebo.
• Participants were monitored for about eight weeks.
The most commonly reported side effects were considered standard and like any other vaccination. These included:
• Injection site pain
• And muscle aches
The side effects were generally mild to moderate in severity, with a duration of one or two days. In other words, participants found themselves feeling much the same as they would after an influenza vaccine or "tetanus shot." Once the vaccination was found safe, it was time to understand its effectiveness.