US case series study in children study looking at association of myocarditis with the Pfizer-BioNTech COVID-19 vaccine

Authors: byUK Science Media Centre|Published onAugust 10, 2021: Prof Peter Openshaw

In this case series, 15 cases of myocarditis are described from a single paediatric referral centre in May, June and July 2021.  Each had been given the Pfizer mRNA vaccine between 1 and 6 days prior to diagnosis; children were aged 12-18 years.  In addition to chest pain, most had fever and muscle pain with evidence of inflammation of the heart muscle evident on tests.  All cases were relatively mild and most resolved completely without treatment.  All but one case was male, and most were after the 2nd dose.

The problem with case series of this type is the lack of comparison groups.  How many cases of myocarditis might be seen in normal children, or those given other vaccines (including those that are not for COVID), or in teenagers infected with SARS-CoV-2?

As the authors note, myocarditis does happen after other vaccines.  The estimated rate (62.8 cases per million) makes this a rare event.  To put this in context, the authors point out that COVID-19 vaccination in males aged 12 to 29 years would prevent 11,000 COVID-19 cases, 560 hospitalizations, 138 intensive care unit admissions and 6 deaths compared with 39 to 47 expected case of myocarditis, if the link with the vaccine is causal.

In another recent study that has not yet been peer-reviewed (, the authors estimated that males aged 12 to 17 were most likely to develop myocarditis within three months of catching covid-19, at a rate of about 450 cases per million infections.  Mendel Singer at Case Western Reserve University in Ohio (an author on this study) said: “If you’re focused on heart inflammation, the safer bet is to take the vaccine.”  The calculations on which this statement is based are still under discussion, but my view that teenagers should be considered for vaccination is not changed by this new publication.

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