HSA’s review of Swiss study that reported heart injury associated with COVID-19 mRNA vaccine

The Health Sciences Authority (HSA) is aware of a Swiss study published in the scientific journal, European Journal of Heart Failure, which reported that 22 out of 777 (i.e. 1 in 35) people who received the COVID-19 mRNA booster vaccine had heart injuries.1 HSA has reviewed this study as part of our ongoing safety surveillance of COVID-19 vaccines, and assessed that the benefit-risk profile of the COVID-19 mRNA vaccines remains positive. 

2            The study was conducted on 777 employees in a hospital in Switzerland. It defined heart injury based solely on increased troponin levels.  While troponin levels are a marker for possible heart injury, increased troponin levels are not necessarily a cause for concern, particularly if there are no other corresponding signs or symptoms. The increase in troponin levels observed in the study were mild and transient. Such increases in troponin levels can also be observed after strenuous physical activities. None of the cases had any abnormal electrocardiograph (ECG)2 changes or developed any major adverse cardiac events within 30 days of vaccination. Hence, the observed increased troponin levels should not be interpreted as amounting to heart injury or myocarditis following vaccination.

3            Myocarditis is a recognised but rare potential risk following COVID-19 mRNA vaccination, with reporting rates of 0.2 per 100,000 doses (0.0002%) for the bivalent vaccines and 1.1 per 100,000 doses (0.0011%) for the primary vaccination series of the monovalent vaccines. Of these rare myocarditis cases following vaccination, most were mild, with patients responding well to treatment. A local precautionary measure advising on the avoidance of strenuous physical activity or exercise for two weeks following COVID-19 mRNA vaccination has been implemented since September 2021 to mitigate this rare risk. The risk of myocarditis with COVID-19 infection is higher compared to that associated with COVID-19 vaccination. A study found an additional 4 cases of myocarditis per 100,000 persons infected.3 As such, the benefits of COVID-19 vaccination continue to outweigh the known risks.

4            HSA will continue to closely monitor the safety of all COVID-19 vaccines used in Singapore and will inform members of the public should there be any significant new safety concerns.



1 Buergin, N., Lopez-Ayala, P., Hirsiger, JR. et al. Sex-specific differences in myocardial injury incidence after COVID-19 mRNA-1273 booster vaccination. Eur J Heart Fail. 2023 Jul 20. doi: 10.1002/ejhf.2978. Epub ahead of print. PMID: 37470105.

2ECG readings are one of the methods used to determine any abnormality in the way the heart functions.

3 Patone, M., Mei, X.W., Handunnetthi, L. et al. Risks of myocarditis, pericarditis, and cardiac arrhythmias associated with COVID-19 vaccination or SARS-CoV-2 infection. Nat Med (2021). https://doi.org/10.1038/s41591-021-01630-0