Patients can expect normal side effects after they are vaccinated. Side effects may feel like flu and even affect your ability to do daily activities, but they should go away in a few days. This is the immune system responding as it should.
However, patients and healthcare providers can (and in some cases are required to) report side effects and reactions using either v-safe or the Vaccine Adverse Event Reporting System (VAERS.) As people get vaccinated, CDC, FDA, and other federal partners will use these and other systems and data sources to conduct ongoing safety monitoring.