Evaluating the relationship between myocarditis and mRNA vaccination

ABSTRACT

Introduction

Inflammatory conditions affecting the heart and surrounding tissues have been recently reported following mRNA vaccination. Evaluating trends in the epidemiology of these events and possible mechanisms related to vaccination will enhance vaccine safety surveillance and inform best practices for future vaccine campaigns.

Areas covered

Epidemiology of the burden of vaccine-associated myocarditis are reviewed. Key summaries of available data from public health advisory bodies and vaccine safety surveillance databases are critically reviewed. The possible biological pathways for vaccine-associated heart inflammations are introduced. A critical synthesis of available information to inform vaccine recommendations and best practices is provided. The citations were selected by the authors based on PubMed searches of the literature, national vaccine safety surveillance databases and summaries from national public health bodies.

Expert opinion

Myocarditis may be associated with vaccination, through several biological mechanisms. Studies have shown that live viral vaccinations can act as a trigger for hypersensitivity inflammatory reactions, but further work is required to examine how the mRNA formulation may induce these autoimmune responses. Given that the risk of these adverse events is low, and the benefit of protection against disease is so great, the receipt of mRNA vaccines is recommended.

KEYWORDS:

• Mrna vaccines
• myocarditis
• adverse events following immunizations
• COVID-19

Funding

This paper was not funded.

Article highlights

• Myocarditis associated with the receipt of COVID-19 mRNA vaccines has been documented, with the greatest risks in young adult males and following the administration of a second dose

• While the observed numbers of myocarditis exceed expected event rates, it remains a very rare adverse events, with most cases being mild and resolved without complications

• The mechanisms by which mRNA vaccines trigger myocarditis are not well understood, but may be attributable to the antagonization of cardiomyocytes by the SARS-Cov-2 virus, or by autoimmune antibodies generated by the host which provoke hypersensitive inflammatory reactions

Despite the increased risk of myocarditis subsequent to vaccination, the risk of acute myocardial injury during the course of natural COVID-19 infection is substantially higher, which is important for assessing the vaccine benefit-risk profile

Declaration of Interest

M Loeb receives payment for industry advisory boards (Pfizer, Medicago, Merck, Sanofi, Seqirus) and data safety monitoring committee (CanSino Biologics). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Author contributions

All authors (ML, CS) have substantially contributed to the conception and design of this article, interepreting the relevant literature, and have been involved in writing the manuscript and revising it for intellectual content.