

Of 49 197 employees who received the first dose of a COVID-19 vaccine, 12 464 (25%) received the Pfizer-BioNtech vaccine and 36 733 (75%) received the Moderna vaccine. Statistical analyses were conducted using SAS, version 9.4 (SAS Institute), and statistical significance was set at P < .05. We calculated the number and frequency of self-reported cutaneous reactions with 95% confidence intervals using symptom survey respondents by dose as the denominator. Cutaneous reactions included rash or itching (other than the injection site), hives, and/or swelling of the lips, tongue, eyes, or face (eAppendix in the Supplement). For 3 days after vaccination, employees completed daily symptom surveys through a multipronged approach, including email, text message, phone, and smartphone application links. Institutional review board approval was provided by the Mass General Brigham human research committee with a waiver of informed consent. We prospectively studied Mass General Brigham employees who received an mRNA COVID-19 vaccine (first dose: December 16, 2020, to Janufollow-up through FebrueMethods in the Supplement).

Shared Decision Making and Communication.Scientific Discovery and the Future of Medicine.Health Care Economics, Insurance, Payment.Clinical Implications of Basic Neuroscience.Challenges in Clinical Electrocardiography.
