More than 1.6 million people completed post-vaccination surveys in the U.S. between Dec. 14, 2020 and Jan. 13, 2021 as part of the Centers for Disease Control's V-safe program. About 70% of respondents reported pain at the spot where they received the Moderna or Pfizer
injection. In the first week after receiving the vaccine, the most common systemic side effect reported was fatigue.