According to the CDC, side effects and serious reactions to the COVID-19 vaccine are rare, based on data from the first month of use of the Pfizer and Moderna vaccines. Health care workers are required to report adverse events after vaccinations. Out of 14 million vaccine doses administered, only about 7,000 reports were sent, and the overwhelming majority were mild events. Anaphylaxis, a life-threatening allergic reaction, occurred in 62 cases, or 4.5 times for every million vaccine doses, similar to other vaccines. The CDC also collected patient-reported data from v-safe, a system for reporting symptoms through text messages sent to your phone. The majority of the side effects reported were mild, like injection site pain, fatigue, headache and chills. They were most prominent in the first day after injection – and worse with the second dose – but improved on every subsequent day, disappearing by day 3 or 4.