Fewer CV events after COVID-19 vaccine-related myocarditis

In a nationwide French cohort study, myocarditis attributed to COVID-19 mRNA vaccination causes fewer cardiovascular (CV) events at 18 months of follow-up than that attributed to SARS-CoV-2 infection or myocarditis of conventional aetiologies.

While the new data are reassuring, the researchers underscored the need for medical management for up to several months after hospital discharge, particularly in more severe cases, wrote Laura Semenzato from EPI-PHARE Scientific Interest Group in Epidemiology of Health Products, French National Agency for the Safety of Medicines and Health Products and the French National Health Insurance, Saint-Denis, France. [JAMA 2024;doi:10.1001/jama.2024.16380]

Looking at long-term CV prognosis

The study included 4,635 individuals aged 12–49 years who were hospitalized for myocarditis in France between December 2020 and June 2022. Patients were assigned to the post-vaccine or post-COVID-19 infection myocarditis groups based on whether they had received a COVID-19 mRNA vaccine or experienced a COVID-19 infection within the past 7 or 30 days.

The 558 patients with post-vaccine myocarditis were younger (average 25.9 years) and more often male (84 percent); 298 and 3,779 patients, respectively, had post-COVID-19 (31 years, 67 percent male) and conventional myocarditis (28.3 years, 79 percent male). About two-thirds (67 percent) of post-vaccine myocarditis occurred after receiving two vaccine doses.

Compared with conventional myocarditis, the incidence of the primary composite endpoint of hospital readmission for myopericarditis, other cardiovascular events, or all-cause death at 18 months was lower following post-vaccine myocarditis (weighted hazard ratio [HR], 0.55; 95 percent confidence interval [CI], 0.36–0.86). However, the risk was similar with post-COVID-19 myocarditis (weighted HR, 1.04; 95 percent CI, 0.70–01.52).

The results were maintained in a historical analysis, replacing the conventional myocarditis cohort with 2,191 patients hospitalized for myocarditis in 2018 (weighed HR, 0.65; 95 percent CI, 0.40–1.05).

Notably, patients with post-vaccine and post-COVID-19 myocarditis received similar care according to the frequency of medical procedures and pharmacotherapy prescribed over 18 months compared with those with conventional myocarditis.

Who should be followed closely?

“It is reassuring that vaccination-related myocarditis is usually mild,” commented Professor Peter Liu from the University of Ottawa Heart Institute, Canada. However, he said clinicians “must remain vigilant” in following up with these patients, given their young age and the little-known information about how this condition can affect them later.

“Setting a checkup appointment upon discharge is not always straightforward, but should be done for at least 3 months,” Liu recommended. The duration of follow-up needed to rule out conditions such as residual late gadolinium enhancement (LGE) – suggestive of myocardial fibrosis – in patients with vaccine-related myocarditis will depend on patient symptoms, severity, and clinicians’ ability to decipher comorbidities,” he added.

He advised that patients with severe symptoms, particularly rhythm disturbances and left-ventricular function abnormalities, and those with comorbidities should be followed more closely.

When asked if 18 months of follow-up is reasonable, Liu said data out to 5 years are warranted. “Understanding why some people get unusual complications is important to identify those at risk.”