Clinical outcomes of myocarditis after SARS-CoV-2 mRNA vaccination in four Nordic countries: population based cohort study

Healthcare utilization among COVID-19 mRNA vaccine-associated myocarditis cases: a matched retrospective cohort study

OBJECTIVES

We evaluated all-cause healthcare utilization among those with vaccine-associated myocarditis, compared to vaccinees without postvaccination myocarditis.

METHODS

We conducted a retrospective cohort study in individuals aged 12 and older who received COVID-19 mRNA vaccination in British Columbia. Exposure was defined as an ED visit or hospitalization for myocarditis within 21 days postvaccination. The primary outcome was healthcare utilization. Ratios of rate ratios (RRRs) for exposure-associated healthcare utilization were calculated using a difference-in-differences (DiD) analysis.

RESULTS

In the postindex period, the exposed and unexposed groups showed substantial utilization rate difference (RD = 15.30 [95% CI, 14.47-16.13). A 51% overall increase in healthcare utilization was observed over 18 months among exposed individuals (RRR, 1.51 [95%CI, 1.08-2.11]). In the initial six months, healthcare utilization surpassed the 18-month estimate, exhibiting a 125% increase (RRR, 2.25 [95%CI, 1.43-3.52]), while the last 12 months showed no statistically significant change (RRR, 1.03 [95%CI, 0.72-1.47]). An additional 9.1 (95%CI, 8.53-9.71) visits per person were attributed to vaccine-associated myocarditis over 18 months (total excess = 938.26 healthcare visits).

CONCLUSION

The initial surge in healthcare visits postexposure, mainly outpatient follow-ups, followed by a return to baseline rates, indicates a positive prognosis and supports the vaccine's safety profile.

Safety and reactogenicity of the BNT162b2 COVID-19 vaccine: Development, post-marketing surveillance, and real-world data

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to urgent actions by innovators, vaccine developers, regulators, and other stakeholders to ensure public access to protective vaccines while maintaining regulatory agency standards. Although development timelines for vaccines against SARS-CoV-2 were much quicker than standard vaccine development timelines, regulatory requirements for efficacy and safety evaluations, including the volume and quality of data collected, were upheld. Rolling review processes supported by sponsors and regulatory authorities enabled rapid assessment of clinical data as well as emergency use authorization. Post-authorization and pharmacovigilance activities enabled the quantity and breadth of post-marketing safety information to quickly exceed that generated from clinical trials. This paper reviews safety and reactogenicity data for the BNT162 vaccine candidates, including BNT162b2 (Comirnaty, Pfizer/BioNTech COVID-19 vaccine) and bivalent variant-adapted BNT162b2 vaccines, from preclinical studies, clinical trials, post-marketing surveillance, and real-world studies, including an unprecedentedly large body of independent evidence.

Myocarditis Associated with COVID-19 Vaccination

Myocarditis after the COVID-19 vaccine is one of the important adverse events following immunization, observed mainly after mRNA-based vaccines. Importantly, post-vaccination myocarditis was less common than myocarditis after SARS-CoV-2 infection, as it was scored at 19.7 per 1,000,000 doses and 2.76 per 1000 infections. Predominantly, its course was benign and, compared with the myocarditis after COVID-19 infection, significantly fewer patients developed heart failure or died among patients with post-vaccination myocarditis. The group at highest risk of myocarditis related to COVID-19 vaccination were young males who received a second dose of an mRNA vaccine. It was observed that, among mRNA vaccines, specifically mRNA-1273 was associated with a higher risk of myocarditis. The mechanism underlying myocarditis after COVID-19 vaccination is still under investigation and certain processes are being considered. Currently, some follow-up assessments of patients who developed vaccine-induced myocarditis are available and suggest a favorable prognosis. The aim of this review is to discuss the most recent data on myocarditis after COVID-19 vaccination considering its epidemiology, clinical presentation, diagnosis, management, relative risk of myocarditis compared with SARS-CoV-2 infection, potential underlying mechanism, and follow-up data of patients who developed post-vaccination myocarditis.

Using Vaccine Safety Data to Demonstrate the Potential of Pooled Data Analysis

In Canada, vaccine safety studies are often conducted at the provincial/territorial level where the primary data on vaccination reside. Combining health services data from multiple jurisdictions using a pooled data analytic approach would reduce the amount of time needed to detect vaccine safety signals. To determine the difference in the time it would take to identify safety signals using different proportions of the Canadian population, we conducted power and sample size calculations for a hypothetical self-controlled case series-based surveillance analysis. We used scenarios modeled after the real-world examples of myocarditis and vaccine-induced immune thrombotic thrombocytopenia (VITT) following COVID-19 vaccination as our base cases. Our calculations demonstrated that in the case of a myocarditis-type event, a pooled analysis would reduce the time needed to detect a safety signal by over 60% compared to using Ontario data alone. In the case of a VITT-type event, a pooled analysis could detect a safety signal 49 days sooner than using Ontario data alone, potentially averting as many as 30 events. Our analysis demonstrates that there is substantial value in using pan-Canadian health services data to evaluate the safety of vaccines. Efforts should be made to develop a pan-Canadian vaccine data source to allow for an earlier evaluation of suspected adverse events following immunization.

Long-Term Risk of Myocarditis in Patients With Inflammatory Bowel Disease: A Nationwide Cohort Study in Sweden

INTRODUCTION

Despite a suggested link between inflammatory bowel disease (IBD) and myocarditis, the association has not been well established. This study aimed to investigate the long-term risk of myocarditis in patients with IBD.

METHODS

This nationwide cohort involved all patients with biopsy-confirmed IBD in Sweden (1969-2017) (n = 83,264, Crohn's disease [CD, n = 24,738], ulcerative colitis [UC, n = 46,409], and IBD-unclassified [IBD-U, n = 12,117]), general population reference individuals (n = 391,344), and IBD-free full siblings (n = 96,149) and followed until 2019. Primary outcome was incident myocarditis, and secondary outcome was severe myocarditis (complicated with heart failure, death, or readmission). Flexible parametric survival models were used to estimate adjusted hazard ratios (aHRs) and cumulative incidence of outcomes, along with 95% confidence intervals.

RESULTS

During a median follow-up of 12 years, there were 256 myocarditis cases in patients with IBD (incidence rate [IR] = 22.6/100,000 person-years) and 710 in reference individuals (IR = 12.9), with an aHR of 1.55 (95% confidence interval 1.33-1.81). The increased risk persisted through 20 years after IBD diagnosis, corresponding to 1 extra myocarditis case in 735 patients with IBD until then. This increased risk was observed in CD (aHR = 1.48 [1.11-1.97]) and UC (aHR = 1.58 [1.30-1.93]). IBD was also associated with severe myocarditis (IR: 10.1 vs 3.5; aHR = 2.44 [1.89-3.15]), irrespective of IBD subtypes (CD: aHR = 2.39 [1.43-4.01], UC: aHR = 2.82 [1.99-4.00], and IBD-U: aHR = 3.14 [1.55-6.33]). Sibling comparison analyses yielded similar results.

DISCUSSION

Patients with IBD had an increased risk of myocarditis, especially severe myocarditis, for ≥20 years after diagnosis, but absolute risks were low.

Long-Term Prognosis of Patients With Myocarditis Attributed to COVID-19 mRNA Vaccination, SARS-CoV-2 Infection, or Conventional Etiologies

Importance

Although patients with myocarditis after COVID-19 mRNA vaccination appear to have a good prognosis near hospital discharge, their longer-term prognosis and management remain unknown.

Objective

To study the cardiovascular complications of post-COVID-19 mRNA vaccination myocarditis and other types of myocarditis during an 18-month follow-up, as well as disease management based on a study of the frequency of medical procedures and drug prescriptions.

Design, Setting, and Participants

In this cohort study based on the French National Health Data System, all individuals aged 12 to 49 years hospitalized for myocarditis in France between December 27, 2020, and June 30, 2022, were identified.

Exposure

Individuals were categorized as having postvaccine myocarditis (within 7 days after COVID-19 mRNA vaccine), post-COVID-19 myocarditis (within 30 days of SARS-CoV-2 infection), or conventional myocarditis.

Main Outcomes and Measures

The occurrence of clinical outcomes (hospital readmission for myopericarditis, other cardiovascular events, all-cause death, and a composite outcome of these events) over the 18 months following hospital admission were analyzed using weighted Cox models to standardize the comparisons with the conventional myocarditis group. Also, medical management after hospital discharge was longitudinally assessed using generalized estimated equation models.

Results

In total, 4635 individuals were hospitalized for myocarditis: 558 with postvaccine myocarditis, 298 with post-COVID-19 myocarditis, and 3779 with conventional myocarditis. Patients with postvaccine myocarditis were younger than those with post-COVID-19 and conventional myocarditis (mean [SD] age of 25.9 [8.6], 31.0 [10.9], and 28.3 [9.4] years, respectively) and were more frequently men (84%, 67%, and 79%). Patients with postvaccine myocarditis had a lower standardized incidence of the composite clinical outcome than those with conventional myocarditis (32/558 vs 497/3779 events; weighted hazard ratio, 0.55 [95% CI, 0.36-0.86]), whereas individuals with post-COVID-19 myocarditis had similar results (36/298 events; weighted hazard ratio, 1.04 [95% CI, 0.70-1.52]). The standardized frequency of medical procedures and drugs prescribed in patients with postvaccine myocarditis or post-COVID-19 myocarditis followed a similar trend in the 18 months following hospital discharge to that of patients with conventional myocarditis.

Conclusions and Relevance

Patients with post-COVID-19 mRNA vaccination myocarditis, contrary to those with post-COVID-19 myocarditis, show a lower frequency of cardiovascular complications than those with conventional myocarditis at 18 months. However, affected patients, mainly healthy young men, may require medical management up to several months after hospital discharge.

Comprehensive Review of COVID-19: Epidemiology, Pathogenesis, Advancement in Diagnostic and Detection Techniques, and Post-Pandemic Treatment Strategies

At present, COVID-19 remains a public health concern due to the ongoing evolution of SARS-CoV-2 and its prevalence in particular countries. This paper provides an updated overview of the epidemiology and pathogenesis of COVID-19, with a focus on the emergence of SARS-CoV-2 variants and the phenomenon known as 'long COVID'. Meanwhile, diagnostic and detection advances will be mentioned. Though many inventions have been made to combat the COVID-19 pandemic, some outstanding ones include multiplex RT-PCR, which can be used for accurate diagnosis of SARS-CoV-2 infection. ELISA-based antigen tests also appear to be potential diagnostic tools to be available in the future. This paper also discusses current treatments, vaccination strategies, as well as emerging cell-based therapies for SARS-CoV-2 infection. The ongoing evolution of SARS-CoV-2 underscores the necessity for us to continuously update scientific understanding and treatments for it.

Myocarditis associated with COVID-19 vaccination

Following the start of the COVID-19 vaccination campaign, the adverse events of myocarditis and pericarditis were linked mainly to mRNA COVID-19 vaccines by the regulatory authorities worldwide. COVID-19 vaccines have been administered to several million people and the risk of myocarditis post COVID-19 vaccination has been characterised in great detail. At the present time the research data available are scarce and there is still no clear understanding of the biological mechanism/s responsible for this disease. This manuscript provides a concise overview of the epidemiology of myocarditis and the most prominent mechanistic insights in the pathophysiology of the disease. Most importantly it underscores the needed next steps in the research agenda required to characterize the pathophysiology of this disease post-COVID-19 vaccination. Finally, it shares our perspectives and considerations for public health.

Safety outcomes following COVID-19 vaccination and infection in 5.1 million children in England

The risk-benefit profile of COVID-19 vaccination in children remains uncertain. A self-controlled case-series study was conducted using linked data of 5.1 million children in England to compare risks of hospitalisation from vaccine safety outcomes after COVID-19 vaccination and infection. In 5-11-year-olds, we found no increased risks of adverse events 1-42 days following vaccination with BNT162b2, mRNA-1273 or ChAdOX1. In 12-17-year-olds, we estimated 3 (95%CI 0-5) and 5 (95%CI 3-6) additional cases of myocarditis per million following a first and second dose with BNT162b2, respectively. An additional 12 (95%CI 0-23) hospitalisations with epilepsy and 4 (95%CI 0-6) with demyelinating disease (in females only, mainly optic neuritis) were estimated per million following a second dose with BNT162b2. SARS-CoV-2 infection was associated with increased risks of hospitalisation from seven outcomes including multisystem inflammatory syndrome and myocarditis, but these risks were largely absent in those vaccinated prior to infection. We report a favourable safety profile of COVID-19 vaccination in under-18s.

Booster vaccination with SARS-CoV-2 mRNA vaccines and myocarditis in adolescents and young adults: a Nordic cohort study

BACKGROUND AND AIMS

The SARS-CoV-2 mRNA vaccines are associated with an increased risk of myocarditis. This association appears to be strongest in male adolescents and younger males and after the second dose. The aim was to evaluate the risk of myocarditis following SARS-CoV-2 mRNA booster vaccination in 12-to-39-year-olds.

METHODS

A multinational cohort study was conducted using nationwide register data in Denmark, Finland, Norway, and Sweden and comprising all 8.9 million individuals residing in each of the four countries. Participants were followed for an inpatient diagnosis of myocarditis. In each of the four countries, Poisson regression was used to estimate adjusted incidence rate ratios (IRRs) of myocarditis comparing vaccination schedules, with associated 95% confidence intervals (CIs). Country-specific results were combined in meta-analyses.

RESULTS

A total of 8.9 million residents were followed for 12 271 861 person-years and 1533 cases of myocarditis were identified. In 12-to-39-year-old males, the 28-day acute risk period following the third dose of BNT162b2 or mRNA-1273 was associated with an increased incidence rate of myocarditis compared to the post-acute risk period 28 days or more after the second dose [IRR 2.08 (95% CI 1.31-3.33) and 8.89 (2.26-35.03), respectively]. For females, the corresponding IRR was only estimable for BNT162b2, 3.99 (0.41-38.64). The corresponding absolute risks following the third dose of BNT162b2 and mRNA-1273 in males were 0.86 (95% CI 0.53-1.32) and 1.95 (0.53-4.99) myocarditis events within 28 days per 100 000 individuals vaccinated, respectively. In females, the corresponding absolute risks following the third dose of BNT162b2 were 0.15 (0.04-0.39) events per 100 000 individuals vaccinated. No deaths occurred within 30 days of vaccine-related cases.

CONCLUSIONS

The results suggest that a booster dose is associated with increased myocarditis risk in adolescents and young adults. However, the absolute risk of myocarditis following booster vaccination is low.

Drug-induced cardiac toxicity and adverse drug reactions, a narrative review

Drug-induced cardiotoxicity is a primary concern in both drug development and clinical practice. Although the heart is not a common target for adverse drug reactions, some drugs still cause various adverse cardiac events, with sometimes severe consequences. Direct cardiac toxicity encompasses functional and structural changes of the cardiovascular system due to possible exposure to medicines. This phenomenon extends beyond cardiovascular drugs to include non-cardiovascular drugs including anticancer drugs such as tyrosine kinase inhibitors, anthracyclines and immune checkpoint inhibitors (ICIs), as well as various antipsychotics, venlafaxine, and even some antibiotics (such as macrolides). Cardiac ADRs comprise an array of effects, ranging from heart failure and myocardial ischemia to valvular disease, thrombosis, myocarditis, pericarditis, arrhythmias, and conduction abnormalities. The underlying mechanisms may include disturbances of ionic processes, induction of cellular damage via impaired mitochondrial function, and even hypercoagulability. To mitigate the impact of drug-induced cardiotoxicity, multi-stage evaluation guidelines have been established, following the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines for in vitro and in vivo testing. Despite preclinical safeguards, post-marketing surveillance remains critical, as certain cardiotoxic drugs may escape initial scrutiny. Indeed, historical data show that cardiovascular ADRs contribute to almost 10% of market withdrawals. The impact of drug-induced cardiotoxicity on cardiac issues, particularly heart failure, is often underestimated, with incidence rates ranging from 11.0% to over 20.0%. We here comprehensively examine different patterns of drug-induced cardiotoxicity, highlighting current concerns and emerging pharmacovigilance signals. Understanding the underlying mechanisms and the associated risk factors is critical in order to promptly identify, effectively manage, and proactively prevent drug-induced cardiac adverse events. Collaborative efforts between physicians and cardiologists, coupled with thorough assessment and close monitoring, are essential to ensuring patient safety in the face of potential drug-induced cardiotoxicity.

Responses to Common Misconceptions Relating to COVID-19 Variant-Adapted mRNA Vaccines

The evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the waning of immunity over time has necessitated the use of booster doses of original coronavirus disease 2019 (COVID-19) vaccines. This has also led to the development and implementation of variant-adapted messenger RNA (mRNA) vaccines that include an Omicron sub-lineage component in addition to the antigen based on the wild-type virus spike protein. Subsequent emergence of the recombinant XBB sub-lineages triggered the development of monovalent XBB-based variant-adapted mRNA vaccines, which are available for vaccination campaigns in late 2023. Misconceptions about new variant-adapted vaccines may exacerbate vaccine fatigue and drive the lack of vaccine acceptance. This article aims to address common concerns about the development and use of COVID-19 variant-adapted mRNA vaccines that have emerged as SARS-CoV-2 has continued to evolve.

Clinical course and follow-up of pediatric patients with COVID-19 vaccine-associated myocarditis compared to non-vaccine-associated myocarditis within the prospective multicenter registry-"MYKKE"

BACKGROUND

Since the onset of widespread COVID-19 vaccination, increased incidence of COVID-19 vaccine-associated myocarditis (VA-myocarditis) has been noted, particularly in male adolescents.

METHODS

Patients <18 years with suspected myocarditis following COVID-19 vaccination within 21 days were enrolled in the PedMYCVAC cohort, a substudy within the prospective multicenter registry for pediatric myocarditis "MYKKE." Clinical data at initial admission, 3- and 9-months follow-up were monitored and compared to pediatric patients with confirmed non-vaccine-associated myocarditis (NVA-myocarditis) adjusting for various baseline characteristics.

RESULTS

From July 2021 to December 2022, 56 patients with VA-myocarditis across 15 centers were enrolled (median age 16.3 years, 91% male). Initially, 11 patients (20%) had mildly reduced left ventricular ejection fraction (LVEF; 45%-54%). No incidents of severe heart failure, transplantation or death were observed. Of 49 patients at 3-months follow-up (median (IQR) 94 (63-118) days), residual symptoms were registered in 14 patients (29%), most commonly atypical intermittent chest pain and fatigue. Diagnostic abnormalities remained in 23 patients (47%). Of 21 patients at 9-months follow-up (259 (218-319) days), all were free of symptoms and diagnostic abnormalities remained in 9 patients (43%). These residuals were mostly residual late gadolinium enhancement in magnetic resonance imaging. Patients with NVA-myocarditis (n=108) more often had symptoms of heart failure (P = .003), arrhythmias (P = .031), left ventricular dilatation (P = .045), lower LVEF (P < .001) and major cardiac adverse events (P = .102).

CONCLUSIONS

Course of COVID-19 vaccine-associated myocarditis in pediatric patients seems to be mild and differs from non-vaccine-associated myocarditis. Due to a considerable number of residual symptoms and diagnostic abnormalities at follow-up, further studies are needed to define its long-term implications.

A descriptive review on the real-world impact of Moderna, Inc. COVID-19 vaccines

INTRODUCTION

Since the original COVID-19 vaccines were developed, abundant clinical trial and real-world evidence evaluating the efficacy, effectiveness, and safety of COVID-19 vaccines has been collected. Knowledge of the relative benefits and risks of COVID-19 vaccines is essential for building trust within target populations, ensuring they remain effectively and safely protected against an enduring infectious threat.

AREAS COVERED

This descriptive review discusses the benefits and risks associated with marketed Moderna, Inc. mRNA-based COVID-19 vaccines, focusing on their real-world effectiveness and safety profiles in various age groups. Adverse events of interest and potential benefits of vaccination are reviewed, including reduced risk for severe COVID-19 and long-term health outcomes, reduced economic and societal costs, and reduced risk for SARS-CoV-2 transmission.

EXPERT OPINION

Post-marketing safety and real-world data for Moderna, Inc. COVID-19 mRNA vaccines strongly support a positive benefit - risk profile favoring vaccination across all age groups. Although COVID-19 is no longer considered a global health pandemic, health risks associated with SARS-CoV-2 infection remain high. Concerted efforts are required to engage communities and maintain protection through vaccination. Continued surveillance of emerging variants and monitoring of vaccine safety and effectiveness are crucial for ensuring sustained protection against SARS-CoV-2.

Risk of myocarditis and pericarditis after a COVID-19 mRNA vaccine booster and after COVID-19 in those with and without prior SARS-CoV-2 infection: A self-controlled case series analysis in England

BACKGROUND

An increased risk of myocarditis or pericarditis after priming with mRNA Coronavirus Disease 2019 (COVID-19) vaccines has been shown but information on the risk post-booster is limited. With the now high prevalence of prior Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, we assessed the effect of prior infection on the vaccine risk and the risk from COVID-19 reinfection.

METHODS AND FINDINGS

We conducted a self-controlled case series analysis of hospital admissions for myocarditis or pericarditis in England between 22 February 2021 and 6 February 2022 in the 50 million individuals eligible to receive the adenovirus-vectored vaccine (ChAdOx1-S) for priming or an mRNA vaccine (BNT162b2 or mRNA-1273) for priming or boosting. Myocarditis and pericarditis admissions were extracted from the Secondary Uses Service (SUS) database in England and vaccination histories from the National Immunisation Management System (NIMS); prior infections were obtained from the UK Health Security Agency's Second-Generation Surveillance Systems. The relative incidence (RI) of admission within 0 to 6 and 7 to 14 days of vaccination compared with periods outside these risk windows stratified by age, dose, and prior SARS-CoV-2 infection for individuals aged 12 to 101 years was estimated. The RI within 27 days of an infection was assessed in the same model. There were 2,284 admissions for myocarditis and 1,651 for pericarditis in the study period. Elevated RIs were only observed in 16- to 39-year-olds 0 to 6 days postvaccination, mainly in males for myocarditis. Both mRNA vaccines showed elevated RIs after first, second, and third doses with the highest RIs after a second dose 5.34 (95% confidence interval (CI) [3.81, 7.48]; p < 0.001) for BNT162b2 and 56.48 (95% CI [33.95, 93.97]; p < 0.001) for mRNA-1273 compared with 4.38 (95% CI [2.59, 7.38]; p < 0.001) and 7.88 (95% CI [4.02, 15.44]; p < 0.001), respectively, after a third dose. For ChAdOx1-S, an elevated RI was only observed after a first dose, RI 5.23 (95% CI [2.48, 11.01]; p < 0.001). An elevated risk of admission for pericarditis was only observed 0 to 6 days after a second dose of mRNA-1273 vaccine in 16 to 39 year olds, RI 4.84 (95% CI [1.62, 14.01]; p = 0.004). RIs were lower in those with a prior SARS-CoV-2 infection than in those without, 2.47 (95% CI [1.32,4.63]; p = 0.005) versus 4.45 (95% [3.12, 6.34]; p = 0.001) after a second BNT162b2 dose, and 19.07 (95% CI [8.62, 42.19]; p < 0.001) versus 37.2 (95% CI [22.18, 62.38]; p < 0.001) for mRNA-1273 (myocarditis and pericarditis outcomes combined). RIs 1 to 27 days postinfection were elevated in all ages and were marginally lower for breakthrough infections, 2.33 (95% CI [1.96, 2.76]; p < 0.001) compared with 3.32 (95% CI [2.54, 4.33]; p < 0.001) in vaccine-naïve individuals respectively.

CONCLUSIONS

We observed an increased risk of myocarditis within the first week after priming and booster doses of mRNA vaccines, predominantly in males under 40 years with the highest risks after a second dose. The risk difference between the second and the third doses was particularly marked for the mRNA-1273 vaccine that contains half the amount of mRNA when used for boosting than priming. The lower risk in those with prior SARS-CoV-2 infection, and lack of an enhanced effect post-booster, does not suggest a spike-directed immune mechanism. Research to understand the mechanism of vaccine-associated myocarditis and to document the risk with bivalent mRNA vaccines is warranted.

SARS-CoV-2, vaccination or autoimmunity as causes of cardiac inflammation. Which form prevails?

The causes of cardiac inflammation during the COVID-19 pandemic are manifold and complex, and may have changed with different virus variants and vaccinations. The underlying viral etiology is self-evident, but its role in the pathogenic process is diverse. The view of many pathologists that myocyte necrosis and cellular infiltrates are indispensable for myocarditis does not suffice and contradicts the clinical criteria of myocarditis, i.e., a combination of serological evidence of necrosis based on troponins or MRI features of necrosis, edema, and inflammation based on prolonged T1 and T2 times and late gadolinium enhancement. The definition of myocarditis is still debated by pathologists and clinicians. We have learned that myocarditis and pericarditis can be induced by the virus via different pathways of action such as direct viral damage to the myocardium through the ACE2 receptor. Indirect damage occurs via immunological effector organs such as the innate immune system by macrophages and cytokines, and then later the acquired immune system via T cells, overactive proinflammatory cytokines, and cardiac autoantibodies. Cardiovascular diseases lead to more severe courses of SARS-CoV‑2 disease. Thus, heart failure patients have a double risk for complicated courses and lethal outcome. So do patients with diabetes, hypertension, and renal insufficiency. Independent of the definition, myocarditis patients benefitted from intensive hospital care, ventilation, if needed, and cortisone treatment. Postvaccination myocarditis and pericarditis affect primarily young male patients after the second RNA vaccine. Both are rare events but severe enough to deserve our full attention, because treatment according to current guidelines is available and necessary.

Diagnosis of Acute Myocarditis Following mRNA Vaccines against SARS-CoV-2: A Methodological Review

The occurrence of acute myocarditis following the administration of mRNA vaccines against SARS-CoV-2 remains relatively rare, and it is associated with a very low mortality rate. The incidence varied by vaccine type, sex, and age and after the first, second, or third vaccination dose. However, the diagnosis of this condition often remains challenging. To further elucidate the relationship between myocarditis and SARS-CoV-2 mRNA vaccines, starting with two cases observed at the Cardiology Unit of the West Vicenza General Hospital located in the Veneto Region, which was among the first Italian areas hit by the COVID-19 pandemic, we performed a review of the available literature to highlight the clinical and diagnostic elements that could contribute to suspicion of myocarditis as an adverse event of SARS-CoV-2 immunization.