Montgomery J, Ryan M, Engler R, et al. - Findings call for vigilance for rare adverse events, including myocarditis, following COVID-19 vaccination. However, it should not be translated to diminish overall confidence in vaccination during the current pandemic.

• This is a retrospective case series of patients (n=23) within the US Military Health System who suffered myocarditis post-COVID-19 vaccination between January and April 2021 (22 currently serving in the military and 1 retiree).

• The BNT162b2-messenger RNA (mRNA) vaccine and the mRNA-1273 vaccine were received by seven and 16 patients, respectively.

• Occurrence of myocarditis after receipt of an mRNA COVID-19 vaccine was evident in previously healthy military patients with similar clinical presentations.

• Myocarditis was detected within 4 days of receipt of a COVID-19 vaccine.

• The diagnosis in the majority of patients (n = 20) was made following the second dose of mRNA COVID-19 vaccine; these episodes happened against the backdrop of 2.8 million doses of mRNA COVID-19 vaccines delivered.

• Brief supportive care was provided to all patients and they were recovered or recovering at the time of this report.