Unvaccinated COVID-19 Infection Tied to Higher Myocarditis Risk

Children and young adults who were unvaccinated and infected with COVID-19 were at an increased risk of developing myocarditis, pericarditis, and mortality when compared with those who were vaccinated against COVID-19 with the Pfizer-BioNTech vaccine and not infected.¹

The recent findings published in Vaccine underscored the BNT162b2 vaccine’s favorable benefit profile, particularly for children and young adults. Prior research, also published in Vaccine, described COVID-19 vaccinations in general as reducing the risk of severe or prolonged disease—such as long COVID—in adolescents.² These data, in tandem with the more recent study, provide ample evidence supporting preventive action against COVID-19 for children and adults.

COVID-19 vaccination rates for children under 18 nearly doubled from a cumulative 4.4% in October 2025 to roughly 9% by early 2026, then remained steady through the spring.³ However, overall vaccination rates are waning for kindergarteners, specifically, now at an even lower rate than they were before the pandemic, which experts attribute to a growing mistrust in vaccines.^1,4

Speculation surrounding myocarditis and mortality associated with COVID-19 vaccination is growing despite limited evidence to support the claim.¹ Researchers conducted this study in part to help clarify public confusion and disprove any related misinformation. Their findings highlighted that the public’s concern over the relative risk (RR) thought to be associated with the COVID-19 vaccine actually increases in likelihood if the child or young adult was infected and unvaccinated vs those who are vaccinated.¹

How Researchers Compared Infection and Vaccination Outcomes

The multi-center cohort study used de-identified electronic health records (EHR) from the TriNetX US Collaborative Network. The Pfizer-BioNTech vaccine took precedence as a control because it was among the earliest authorized for adolescents and the most common among those in the TriNetX network.

There were a total of 4,072,375 individuals aged 16–25, of whom 45.2% were male, with a mean age of 20.8 years. Participants were categorized into 4 mutually exclusive exposure cohorts based on EHR records: uninfected/unvaccinated, infected/unvaccinated, vaccinated/uninfected, and hybrid immunity, defined as those infected with SARS-CoV-2 before receiving their vaccination.

The infected/unvaccinated group had the highest cumulative incidence of mortality (0.084%), pericarditis (0.035%), and myocarditis (0.116%) among the 4 cohorts. By contrast, the vaccinated/uninfected group had the lowest cumulative incidence of each, respectively.

Vaccination Was Linked to Lower Risk of Myocarditis, Pericarditis, and Death

After 1:1 propensity score matching, data showed that a SARS-CoV-2 infection was associated with a markedly higher risk of myocarditis (RR, 4.91; 95% CI, 3.11–7.77), pericarditis (RR, 1.93; 95% CI, 1.39–2.67), and mortality (RR, 1.33; 95% CI, 1.04–1.71). In comparison, vaccination was shown to significantly reduce the risk of mortality (RR, 0.27; 95% CI, 0.18–0.41) and pericarditis (RR, 0.33; 95% CI, 0.20–0.53); myocarditis risk was lower but not statistically significant (RR, 0.57; 95% CI, 0.28–1.16).

When comparing the vaccinated/uninfected group with the infected/unvaccinated group, the former demonstrated substantially lower recorded risks: 72% lower mortality, 79% lower pericarditis, and 85% lower myocarditis (all P < .001).

“These estimates assume the observed associations are causal, including the reduction in all-cause mortality,” the study authors wrote. “Because that mortality reduction may be driven partly by who chooses vaccination rather than by the vaccine itself, the projected numbers averted should be read as illustrative rather than exact.”

Although rare, vaccine-associated myocarditis typically occurs in adolescent and young adult males within 2–3 days of the second mRNA dose. However, it is usually mild and resolves on its own quickly.

The study was limited as researchers cited some vaccination records as missing, which explains the low recorded vaccination rate. Infected individuals also undergo more testing, suggesting a reason why their myocarditis and pericarditis records may be more complete when compared with the uninfected groups—a gap that could inflate the infection-associated risk estimates.

“Real-world evidence, active surveillance, and open comparative analysis will remain essential for guiding vaccine policy and public communication,” the study authors concluded.

References

1. Toraih EA, Hussein MH, Thomas SJ, Aiash H. Cardiac outcomes following SARS-CoV-2 infection versus BNT162b2 vaccination in adolescents and young adults: a cohort study of 4 million individuals. Vaccine. 2026;91:129001. doi:10.1016/j.vaccine.2026.129001

2. McCormick B. COVID-19 vaccination linked to lower risk of long COVID in adolescents. AJMC^®. November 3, 2025. Accessed August 27, 2026. https://www.ajmc.com/view/covid-19-vaccination-linked-to-lower-risk-of-long-covid-in-adolescents

3. CDC. Vaccination trends. CDC. August 21, 2026. Accessed August 27, 2026. https://www.cdc.gov/respiratory-viruses/data/vaccination-trends.html

4. Stobbe M. Kindergarten vaccination rates inch down yet again; exemptions reach record high. ABC7. August 19, 2026. Accessed August 27, 2026. https://abc7ny.com/post/kindergarten-vaccination-rates-inch-down-exemptions-reach-record-high/19702865/