MHRA Reports Latest UK Data on COVID-19 Vaccine Adverse Events

Dawn O'Shea

August 25, 2021

The Medicines and Healthcare products Regulatory Agency (MHRA) has received reports of almost 1.15 million suspected adverse events associated with COVID-19 vaccines.

In its latest report, the MHRA reports that, as of 11 August 2021, it has received 104,446 Yellow Cards for the Pfizer/BioNTech vaccine, 228,239 for the AstraZeneca vaccine, 13,325 for the Moderna vaccine and an additional 1022 have been reported where the brand of the vaccine was not specified.

The Yellow Cards included reports of 1,148,675 suspected reactions, including 293,779 with Pfizer, 813,622 with AstraZeneca and 41,274 with the Moderna vaccine.

The overall Yellow Card reporting rate for the three vaccines in the UK has been in the order of three to seven per 1000 doses administered.

The vast majority of reports have related to injection-site reactions and generalised flu-like symptoms, with headache, chills, fatigue, nausea, fever, dizziness, weakness, myalgia and tachycardia. The nature of the suspected side effects has been broadly similar across age groups, although, as is to be expected, events were more likely to be reported in younger adults.

However, there have been 501 reports of deaths associated with suspected adverse reactions to the Pfizer/BioNTech vaccine, as well as 1053 following administration of the AstraZeneca and 14 with Moderna vaccines. A further 28 deaths were reported but the brand of vaccine was unspecified. The majority of reported deaths occurred in elderly people or people with underlying illness.

The MHRA stressed that the "usage of the vaccines has increased over the course of the campaigns and as such, so has reporting of fatal events with a temporal association with vaccination however, this does not indicate a link between vaccination and the fatalities reported."


The agency has received 461 reports of anaphylaxis or anaphylactoid reactions with the Pfizer vaccine, along with 30 reports of anaphylaxis following administration of the Moderna vaccine and 808 reports associated with the AstraZeneca vaccine.

The current MHRA advice is that those with a previous history of allergic reactions to the ingredients of the vaccine should not receive it.

Thromboembolic events

As of 11 August 2021, a total of 412 cases of major thromboembolic events with concurrent thrombocytopenia were reported following administration of the AstraZeneca vaccine. Of these, 42 were reported after the second dose. Cases were documented in 210 women and 200 men aged 18-93 years.

Cerebral venous sinus thrombosis was reported in 147 cases, with an average age of 49 years. A total of 265 had other thromboembolic events (average age, 54 years) with concurrent thrombocytopenia.

The overall incidence after first or unknown dose stands at 14.9 cases per million doses, which drops to 1.8 per million second doses. There appears to be a higher incidence in younger adult groups after the first dose—20.2 per million doses in those aged 18-49 years compared with 11.0 per million in people aged 50 years and older.

There is also some evidence that the incidence is higher in females, although this has not been seen across all age groups and the difference remains small.

There have been 73 reported associated deaths, representing an overall case fatality rate of 18 per cent.

A total of 15 cases of major thromboembolic events with concurrent thrombocytopenia have been reported following use of the Pfizer vaccine, with a fatality rate of 7 per cent (1 death). Only two cases have been reported following administration of the Moderna vaccine, both in adult males under the age of 50 years, with no deaths reported.

Myocarditis and pericarditis

The MHRA has been carefully monitoring the incidence of myocarditis and pericarditis following use of the Pfizer vaccine. As of 11 August 2021, the agency has received 182 reports of myocarditis and 153 reports of pericarditis associated with the vaccine, as well as three reports of viral pericarditis and one report each of infective pericarditis and streptococcal endocarditis.

A further 93 cases of myocarditis and 145 cases of pericarditis have been reported in connection with the AstraZeneca vaccine, along with five cases of viral pericarditis, two reports of bacterial endocarditis and one report each of viral myocarditis, infectious myocarditis and acute endocarditis.

In relation to Moderna, there have been 33 reports of myocarditis, 28 reports of pericarditis and one report of endocarditis.

The overall reporting rate of myocarditis and pericarditis with the Pfizer vaccine are 5.0 and 4.3 cases per million doses, respectively. For Moderna, the figures are 16.6 and 14.0 per million doses, respectively, while the rates with the AstraZeneca vaccine are 2.0 and 3.1 cases per million doses.

In its latest update, the MHRA says it has undertaken a thorough review of both UK and international reports of myocarditis and pericarditis following vaccination. It said there has been a recent increase in reporting of these events, in particular with the Pfizer/BioNTech and Moderna vaccines, with a consistent pattern of cases occurring more frequently in young males and shortly after the second dose of the vaccines. Cases remain extremely rare, and the events are typically mild, with individuals usually recovering within a short time with standard treatment and rest.

The agency says that, given the “widespread use of these vaccines across the UK, the vast majority of suspected adverse reaction reports so far confirm the safety profile seen in clinical trials."

It is important to stress that events reported through the Yellow Card process should not be interpreted as proven side effects associated with a vaccine. Furthermore, the figures must be considered in the context of the number of vaccine doses administered to date. At 47 million people in the UK have now received their first vaccine dose and more than 40 million have received their second dose.

This article originally appeared on Univadis, part of the Medscape Professional Network.


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