“Background
Cases of adolescents and young adults developing myocarditis after vaccination with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–targeted mRNA vaccines have been reported globally, but the underlying immunoprofiles of these individuals have not been described in detail…
Methods
Patient Enrollment and Sample Collection: Adolescents or young adults presenting with myocarditis after SARS-CoV-2 mRNA vaccination, along with healthy, vaccinated control subjects and children with MIS-C, were enrolled...
Results
Sixty-one adolescents and young adults between 12 and 21 years of age, including 16 individuals with vaccine-associated myocarditis, provided a blood sample for analysis... The majority of individuals with postvaccine myocarditis were male (n=13 of 16; 81%), and symptom onset typically occurred within the first week after vaccination.
... [T]otal leukocytes, specifically neutrophils, were significantly increased in individuals with postvaccine myocarditis compared with vaccinated control subjects... These results suggest that postvaccine myocarditis is associated with normal adaptive and T-cell immunity but modest innate activation.
Discussion
... We discovered that individuals who developed postvaccine myocarditis uniquely exhibit elevated levels of free spike protein in circulation, unbound by anti-spike antibodies, which appear to correlate with cardiac troponin T levels and innate immune activation with cytokine release.”
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