Myocarditis warning for Pfizer and Moderna COVID-19 vaccines

Prescribing information for the Pfizer/BioNTech and Moderna COVID-19 vaccines has been updated following very rare reports of myocarditis and pericarditis.

Symptoms of myocarditis and pericarditis include chest pain, shortness of breath, palpitations and arrhythmias. | GETTY IMAGES
Symptoms of myocarditis and pericarditis include chest pain, shortness of breath, palpitations and arrhythmias. | GETTY IMAGES

Healthcare professionals should be alert to the signs and symptoms of myocarditis and pericarditis in patients given the Pfizer/BioNTech or Moderna COVID-19 vaccines, the MHRA has advised. 

Patients should be advised to seek immediate medical attention should they experience new onset of chest pain, shortness of breath or symptoms of arrhythmia after receiving either of the mRNA vaccines, the MHRA says.

Yellow card reports

As of 16 June 2021, the MHRA had received 87 Yellow Card reports of myocarditis and pericarditis as suspected side-effects after administration of the Pfizer/BioNTech COVID-19 vaccine and 4 reports after the Moderna COVID-19 vaccine. Up to the same date an estimated 16.8 million first doses and 10.9 million second doses of the Pfizer/BioNTech vaccine had been administered, and an approximate 0.73 million first doses of the Moderna jab have also now been given.

Similar cases have also been reported internationally following receipt of the Pfizer/BioNTech and Moderna vaccines. These have occurred most frequently in younger males aged 40 years and younger and within 10 days after the second dose. Most of these cases were mild and individuals typically recovered within a short time and with symptomatic treatment and rest.

Although reports of myocarditis and pericarditis after vaccination with the AstraZeneca COVID-19 vaccine have been received, the MHRA says there is insufficient evidence to recommend similar warnings for this vaccine.

Diagnosis of myocarditis and pericarditis typically requires targeted procedures such as electrocardiograms, cardiac imaging, and biomarker analysis, and it is also important to exclude other potential causes for the symptoms, says the MHRA. Treatment of more symptomatic patients will occasionally require relevant expert follow up that might need detailed cardiac imaging to determine the nature of the condition.

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