A booster dose following a primary series provides additional protection against COVID-19. So far, reactions reported after the third mRNA dose were similar to that of the two-dose series: fatigue and pain at injection site were the most commonly reported side effects, and overall, most symptoms were mild to moderate.
However, as with the two-dose series, serious side effects are rare, but may occur. After vaccination, be sure to register for V-safe, the after-vaccination health checker. Learn more about the safety monitoring of COVID-19 booster doses.