It can be hard to tease out COVID-19 vaccine side effects from acute SARS-CoV-2 infection since both can produce systemic symptoms of fever, chills, fatigue, headache, muscle pain, and joint pain.

You may get questions about this from individuals who recently received their COVID-19 vaccine.

Common side effects after COVID-19 vaccination include pain, redness, and swelling in the arm where the vaccine was received.  Systemic symptoms are less common.

Most side effects are mild to moderate, occurring in the first 3 days of vaccination, get better within 1-2 days, and are more frequent and severe after the 2nd dose of mRNA vaccines and among younger people. More information on post-vaccination symptoms for each COVID-19 vaccine can be found at the following links: Pfizer-BioNTech, Moderna, and Janssen.

• In contrast, cough, shortness of breath, rhinorrhea, sore throat or loss of taste or smell are not consistent with post-vaccination symptoms and instead could be symptoms of SARS-CoV-2 infection or another infectious disease.
• If any of these latter symptoms occur after vaccination, SARS-CoV-2 infection should be considered and evaluated for. 
• Also, if systemic symptoms persist longer than is usual after vaccination, another cause should be looked for.
• Ultimately, clinical judgement should be used to determine the likelihood of SARS-CoV-2 infection versus post-vaccination symptoms and the indicated clinical approach.

Resources:

Possible Side Effects After Getting a COVID-19 Vaccine

Post-vaccination Considerations for Workplaces

Post Vaccine Considerations for Residents