The Oxford/AstraZeneca COVID-19 vaccine and blood clots: Understanding the latest information

Posted on April 8th 2021

We understand that some people in our PH community may be worried following the announcement yesterday (7th April) that those under 30 will be offered alternatives to the Oxford/AstraZeneca COVID-19 vaccine.

The decision follows a review by the Medicines and Healthcare products Regulatory Agency (MHRA) which shows people given a dose of this vaccine have an extremely low risk of about four in one million of developing a blood clot.

In an independent report, the Joint Committee on Vaccination and Immunisation (JCVI) said the benefits of the Oxford/AstraZeneca vaccine “far outweigh the risk of adverse events for individuals 30 years of age and over and those who have underlying health conditions which put them at high risk of severe COVID-19 disease.”

In a statement, Professor Sir Munir Pirmohamed, chairman of the Commission on Human Medicines, said the risks had to be weighed against the consequences of COVID-19, which also causes clotting.

He said 7.8% of coronavirus patients suffer blood clots on the lungs, while 11.2% will suffer deep vein thrombosis (DVT) in the legs.

This is compared to the 0.004% risk of developing a blot clot from the Oxford/AstraZeneca vaccine.

Iain Armstrong, chair of the PHA UK said: “We support this statement, which is based on peer-reviewed evidence, and shows a far higher percentage of people develop clots as result of COVID-19 than those who have developed them as a result of the Oxford/AstraZeneca COVID-19 vaccine.

To put it into context, if you travel 250 miles in a car, you also have a one-in-a-million chance of dying. Nothing in life is without risk, and the risks from COVID-19 are far greater than those from any vaccine.

It is vitally important that people with pulmonary hypertension – and the wider population –  receive their COVID-19 vaccines to protect themselves from the risk of serious disease or death.”

The MHRA advises that if you are under 30 and have already received a first dose of the Oxford/AstraZeneca COVID-19 vaccine, you should be given your second dose to complete your protection. The only exception is in those who have developed one of the rare clots after the first dose.

In a UK Government press release, Dr June Raine, MHRA Chief Executive, said: “The public’s safety is always at the forefront of our minds and we take every report of a suspected side effect very seriously indeed. We thoroughly analyse each and every report as we receive it and although the number of reports of CVST [cerebral venous sinus thrombosis] and other thromboembolic events has increased over the last week, so has the overall number of vaccinations administered, therefore these blood clots remain extremely rare and unlikely to occur.”

The UK vaccination programme has been very successful with more than 30 million people vaccinated.