Cardiac Complications After SARS-CoV-2 Infection and mRNA COVID-19 Vaccination — PCORnet, United States, January 2021–January 2022

Myocarditis and/or pericarditis risk after mRNA COVID-19 vaccination: A Canadian head to head comparison of BNT162b2 and mRNA-1273 vaccines

“…In Canada, approximately 17.35% of the vaccinated population have received mixed mRNA vaccine schedules based on national advice from spring 2021 to facilitate series completion and vaccine rollout; it is unknown what the impact of mixed schedules is on reporting rates used in this analysis, as it does not account for the type of dose 1 vaccine received when the report is for a recipient of their second dose. The current literature estimates the rate of myocarditis and/or pericarditis after vaccination is lower than the rates after SARS-CoV-2 infection across all age groups and sexes [39] , [40] , [41] , [42] , [43] . While it is not clear whether this is true for individuals 18-39 using hospital administrative data [42] , or if it holds true when considering mRNA-1273 second dose in males or when examining pericarditis alone [40] , it appears that there is a high proportion of subclinical cases that would not normally be detected outside research studies [45] .…”

Clinical features and burden of post-acute sequelae of SARS-CoV-2 infection in children and adolescents: an exploratory EHR-based cohort study from the RECOVER program

“…Among systemic features, myocarditis was the condition with the strongest association with SARS-CoV-2 infection and is recognized as an important complication in this age group. 30,31 Myositis, encounters for mental health treatment, and respiratory infections including tonsillitis, pneumonia and bronchiolitis were also associated with COVID-19.…”

Childhood Immunity and Infections: Time to Consider Endothelial Cells and Platelets

“…Moreover, growing evidence supports a primary role of the immune system and endothelial/coagulation pathways in the genesis of Long COVID in a subgroup of patients [ 7 ]. Last, differences in immune responses to vaccinations and infection are creating extremely variable susceptibility to reinfections in people of all age groups [ 8 ].…”

“…While COVID-19 was initially considered a respiratory disease, there is now evidence that this is a systemic inflammatory condition characterized by viral invasion potentially in most parts of the organism and endothelial inflammation. Laboratory parameters of endothelial phlogosis and activation of the coagulation cascade is a hallmark of the disease, which has thromboembolic events and myocarditis as a cornerstone of the infection [ 6 , 7 , 8 ]. Conversely, these events are much less frequent in children during COVID-19.…”

“…In Long COVID, chronic inappropriate endothelial and platelet activation, lung hypoperfusion and microclots have been clearly demonstrated [ 7 , 9 ]. Last, a specific group of people (young males) in a minority of cases can develop myocarditis as the main complication of mRNA anti-COVID vaccination [ 8 ], suggesting again a close relationship with cells interfacing with the blood.…”