Update on rare Covid-19 vaccine side effects

14 September 2021

More detailed guidance for health professionals on some rare side effects associated with Covid-19 vaccines has been issued by Public Health England (PHE).

The latest information includes data on rates of myocarditis and pericarditis that have been reported with Pfizer/BioNTech and Moderna vaccines. It also said investigations are ongoing to assess whether reports of Guillain-Barre syndrome after Covid-19 vaccination are related to the jab or would have been expected to occur anyway.

Myocarditis and pericarditis are inflammatory conditions of the heart, with myocarditis incidence difficult to ascertain because most cases are mild and often not well investigated.

The Medicines and Healthcare products Regulatory Agency (MHRA) Commission on Human Medicines Committee said health professionals should be alert to signs and symptoms of myocarditis and pericarditis, with those vaccinated told to seek immediate medical attention if they experience chest pain, shortness of breath or arrhythmia.

PHE has urged doctors to report any suspected case to the MHRA through the Yellow Card scheme as well as collect serum samples to send to PHE to test for antibodies to inform decisions around future vaccination in that individual. 

At 1 September, the MHRA received 238 reports of myocarditis and 189 reports of pericarditis following use of the Pfizer/BioNTech vaccine, and 101 reports of myocarditis and 158 reports of pericarditis for the AstraZeneca vaccine.

The updated PHE information includes figures on vaccination and side effects from US, Israeli and UK databases. It says the rate after first and second doses are 4.3 myocarditis cases per million doses and 3.8 pericarditis cases per million doses for Pfizer/BioNTech, and 14.7 myocarditis cases per million doses and 13.0 pericarditis cases per million doses for Moderna. 

There have also been reports after the AstraZeneca vaccine with a rate of 1.7 myocarditis cases per million doses and 3.0 pericarditis cases per million doses but PHE said these probably reflect the expected background rate of these conditions.

The guidance advises that a history of myocarditis or pericarditis unrelated to Covid-19 vaccination is not a contraindication to receiving a vaccine.

No causal link has been proven between Covid-19 vaccination and Guillain-Barre syndrome, and PHE has advised that anyone who has previously been diagnosed with this syndrome is still recommended to be vaccinated. Anyone who had it after the first dose should still get their second vaccine.

Information for Healthcare Professionals on Myocarditis and Pericarditis Following Covid-19 Vaccination is available here.