A Swiss study published on 20 July 2023 titled “Sex-specific differences in myocardial injury incidence after COVID-19 mRNA-1273 booster vaccination” by Natacha Buergin et al found that “vaccine-associated myocardial injury was more common than previously thought”.
The study period was from 10 December 2021 to 10 February 2022. In total, 1871 employees of the University Hospital Basel were screened, of which 777 were analyzed (540 females [69.5%] and 237 males [30.5%]). The median age was 37 years.
On day 3 after booster administration, a blood sample was taken in order to measure hs-cTnT. If necessary, a follow-up was conducted on day 30. If one believes the textbooks, Troponin T (cTnT) is found in muscle cells with a particular version found in the heart. There should be minimal levels in the blood, so higher levels indicate possible heart muscle cell damage.
Of the 777 subjects, 22 patients suffered myocardial injury although no one suffered major injury within 30 days.
mRNA-1273 vaccine-associated myocardial injury was adjudicated in 22 patients (2.8% [95% CI 1.8–4.3%]), with 20 cases occurring in women (3.7% [95% CI 2.3–5.7%]) and 2 in men (0.8% [95% CI 0.1–3.0%]), with a median age of 46 years (IQR 33–54). This sex difference was statistically significant (p=0.03). On day 3, median hs-cTnT concentration of the 20 women and 2 men with mRNA-1273 vaccine-associated myocardial injury was 13.5 ng/L (IQR 9.0–18.8). It decreased in all but one patient on the follow-up visit to a median value of 6.0 ng/L (IQR 4.0–14.0), being again in the normal range in half of the participants.
Even though 22 of 777 doesn’t seem much, it was still more than expected.
mRNA-1273 booster vaccination-associated elevation of markers of myocardial injury occurred in about one out of 35 persons (2.8%), a greater incidence than estimated in meta-analyses of hospitalized cases with myocarditis (estimated incidence 0.0035%) after the second vaccination.
The observed problems were “mild and transient” but the long-term consequences are still unknown.
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