Fact check: Are there any reported cases of mRNA vaccine-related health issues after 2022?

1. Why myocarditis and pericarditis remain the headline safety story

Multiple sources from 2023–2025 consistently identify myocarditis and pericarditis as the clearest mRNA vaccine safety signal, concentrated in males aged roughly 12–24 and most often occurring shortly after vaccination. The FDA required updated labeling in June 2025 to reflect these risks and quantified incidence estimates around eight cases per million doses for ages six months through 64 years, with higher rates among adolescent and young adult males ^[1]. Observational analyses in national adverse event databases, including Japan, corroborate early onset and age/sex patterns, strengthening the biological plausibility of a vaccine-associated, rare inflammatory cardiac response ^[6].

2. How large reviews and meta-analyses frame overall risk

Systematic reviews and meta-analyses published between 2022 and 2024 describe a spectrum of rare adverse events associated with mRNA vaccines but emphasize that most reported events are uncommon and often mild to moderate and self-limiting. Reviews point to cardiac complications, allergic reactions, thrombocytopenia, and neurological effects while calling for continued long-term study; they do not conclude a high incidence of severe outcomes in the general vaccinated population ^{[2] [3] [7]}. These syntheses weigh different study designs and signal-detection limits, which helps explain why they identify risks but stop short of asserting widespread harm.

3. New signals and what large-scale studies found about other rare events

Large global signal-detection efforts through 2024 identified two rare neurological events—transverse myelitis and acute disseminated encephalomyelitis—as potential signals but ultimately found no association with mRNA vaccines, while confirming myocarditis/pericarditis as a reproducible signal ^[5]. This pattern—initial detection followed by further assessment that rules out some associations but confirms others—illustrates ongoing pharmacovigilance at scale. The global study’s conclusions indicate that while surveillance can detect unexpected patterns, not all early signals withstand more rigorous epidemiologic testing ^[5].

4. The contested claim of rising excess deaths in specific studies

A study cited from the JMA Journal alleges a large excess mortality in Japan after repeated COVID-19 vaccination, claiming excess deaths per million far exceeding U.S. rates and attributing only a fraction to recorded COVID-19 deaths ^[4]. This claim contrasts with regulatory updates and large observational analyses that do not report comparable excess-mortality findings tied to mRNA vaccines; the JMA Journal result is therefore an outlier requiring careful scrutiny of methods, confounder control, and peer review status before being accepted as causal evidence ^{[4] [1]}.

5. Regulatory responses underscore constrained but actionable risks

Regulators acted on consistent myocarditis/pericarditis evidence by updating labels and guidance in 2025, reflecting a policy-level acknowledgement of the risk while maintaining the vaccines’ place in public health strategies for COVID-19 mitigation ^[1]. Label changes and safety communications do not equate to declarations of widespread harm; instead, they indicate that agencies judged the evidence sufficient to change risk communication, particularly for higher-risk demographic subgroups, and to reinforce surveillance and clinical guidance for diagnosis and management ^[1].

6. Real-world clinical trial data and next-generation vaccine findings

Phase 3 trial data for next-generation mRNA constructs reported similar tolerability profiles and non-inferior immunogenicity compared with earlier mRNA vaccines, with local and systemic adverse reactions aligning with prior experience ^[8]. Trials are underpowered to detect very rare events identified in post-market surveillance, so their consistent tolerability complements but does not replace population-level safety monitoring. Trial findings support continued development while underscoring the necessity of robust pharmacovigilance systems post-authorization ^[8].

7. What remains unresolved and the path forward for surveillance

Open questions persist about long-term, very-rare adverse events and the interpretation of discrepant mortality studies; expert consensus and regulatory actions focus on targeted risk communication, ongoing data linkage studies, and international signal evaluation to clarify causality. Systematic reviews endorse continued monitoring and additional long-term studies to quantify rare outcomes’ incidence and recovery trajectories, particularly among younger males and people with prior SARS-CoV-2 infection ^{[2] [7] [3]}. Policymakers and scientists will need transparent data-sharing and standardized methods to reconcile divergent findings.

8. Bottom line for readers weighing the evidence

After 2022, multiple independent lines of evidence and regulatory updates confirm rare myocarditis/pericarditis risks after mRNA COVID-19 vaccination, particularly in younger males, while broader claims of widespread excess mortality linked to mRNA vaccines remain controversial and not supported by the majority of surveillance and review-level evidence cited here ^{[1] [4] [3]}. Continued surveillance, cautious interpretation of outlier studies, and clear clinical guidance remain the principal tools for managing identified risks.