Encephalitis, myocarditis, and thrombocytopenia after COVID-19 mRNA vaccination: Clinical and pathophysiological considerations

Highlights

• COVID-19 vaccination has been associated with rare neurological, cardiac and hematological complications but their causal relationship is not yet fully established. A 15-year-old girl developed, between others and Encephalitis, myocarditis and thrombocytopenia after the second dose of Pfizer BioNTech (BNT162b2) COVID-19 vaccine. We discuss the possibility of crossing the blood-brain barrier by the COVID-19 vaccine excipients and induce hypersensitivity reactions, the excipients inducing hypersensitivity myocarditis and the involvement of platelet surface high affinity IgE (FcεRI) and low affinity IgE (FcεRII/CD23) receptors in inducing platelet aggregation and thrombosis causing increased platelet consumption leading to thrombocytopenia.

• Common materials, in the everyday practice, such as creams, ointments, lotions, cosmetics used by younger persons, especially females, and dental materials and laxatives contain also the same excipients as of COVID-19 vaccines and can sensitize their users. Laxatives have been recently associated with Kounis hypersensitivity coronary. Indeed, the general population is sensitized to cosmetics or dental materials in 1–5.4%. Therefore, hypersensitivity encephalitis, myocarditis and thrombocytopenia could be induced by the vaccine excipients. Alternative excipients have been suggested in vaccine manufacturing if vaccine component-induced hypersensitivity is confirmed by systematic future investigations. In a recent report the authors concluded that hypersensitivity to excipients constitutes risk to patients with allergy to PEG and these patients will await new vaccines containing different excipients.

• It seems that the benefits of vaccination, should be taken into account and the described risks should be also considered in the context of the benefits of COVID-19 vaccination