evidence: - Myocarditis is inflammation of the heart muscle, and pericarditis is inflammation of the outer lining of the heart. Myocarditis and pericarditis after COVID-19 vaccination are rare.1234567911121718192021 Most patients with myocarditis or pericarditis after COVID-19 vaccination responded well to medicine and rest and felt better quickly. [...] - Weintraub ES, Oster ME, Klein NP. Myocarditis or Pericarditis Following mRNA COVID-19 Vaccination. JAMA. 2022 Jun 24; 5(6):e2218512. doi:10.1001/jamanetworkopen.2022.18512 - Hause AM, Zhang B, Yue X, Marquez P, Myers TR, Parker C, Gee J, Su J, Shimabukuro TT, Shay DK. Reactogenicity of Simultaneous COVID-19 mRNA Booster and Influenza Vaccination in the US. JAMA Netw Open 2022 Jul 1;5(7):e2222241.doi: 10.1001/jamanetworkopen.2022.22241.