Coronavirus (COVID-19)—AZ vaccine advice updated in relation to blood clotting

Coronavirus (COVID-19)—AZ vaccine advice updated in relation to blood clotting

The Medicines and Healthcare products Regulatory Agency (MHRA) has issued new advice for the AstraZeneca (AZ) vaccine against coronavirus (COVID-19), based on its finding that blood clots can occur as a side effect of receiving the vaccine.

The MHRA has not recommended age restrictions of the AZ vaccine following its scientific review of the risk of blood clots. The regulator found that a risk of approximately four in a million exists as a side effect of taking the vaccine, with a slightly higher incidence in the younger adult age groups, following the reports that 79 people developed blood clots from 37 million overall jabs. The MRHA has consequently modified its advice to medical professionals to reflect this.

As a precautionary measure, the MHRA has advised against administering the vaccine to those of any age who are at a higher risk of blood clots due to pre-existing medical conditions, unless the benefits of protection from coronavirus outweigh the risk of side effects. Furthermore, the regulator recommends pregnant women to discuss the vaccine with their healthcare professional as pregnancy predisposes to thrombosis (blood clotting).

The regulator also pointed out that the side effect does not seem to occur without a low platelet count and stressed that these symptoms can also occur naturally in unvaccinated people as well as those who have coronavirus.

As a further precautionary measure, MHRA has advised those who experience the following symptoms after receiving the vaccination to seek medical assistance:

• new onset of severe or persistent headache, blurred vision, confusion or seizures

• development of shortness of breath, chest pain, leg swelling or persistent abdominal pain

• unusual skin bruising or pinpoint round spots beyond the injection site

The Joint Committee on Vaccination and Immunisation also issued advice to the government on the use of the AZ vaccine. It stated that it would be preferable to offer alternative vaccines to people under 30 with no underlying health conditions.

The government has responded to the statements by reiterating the safety and effectiveness of the vaccine and has said the benefits of the vaccine far outweigh the risks for the vast majority of adults.

The government has also stated that everyone who received the first dose of the AZ vaccine should receive a second dose of the same brand, irrespective of age, except for the very small number of people who developed blood clots with low platelet counts after their first vaccination. It said that, as a precautionary measure, people under 30 with no underlying health conditions should be offered an alternative vaccine where possible, when this age group becomes eligible.


• MHRA issues new advice, concluding a possible link between COVID-19 Vaccine AstraZeneca and extremely rare, unlikely to occur blood clots

• Statement on AstraZeneca COVID-19 vaccine following MHRA update

• New JCVI advice on use of the AstraZeneca COVID-19 vaccine

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