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Is the Oxford AstraZeneca vaccine safe? A doctor's view

16 March 2021

4:55 PM

16 March 2021

4:55 PM

One of the few positives to have come out of the Covid-19 pandemic has been the remarkable speed at which vaccines have been developed and rolled out in months, rather than the many years that was the previous norm. Their effectiveness is being increasingly proved as more people are vaccinated, and they appear to be extremely well tolerated in terms of side effects.

In the UK at least, vaccine hesitancy does not appear to be as great a problem as was initially feared and no new potential side effects have been reported that were not already known about from the vaccine trial data.

It was therefore something of a surprise last week when European Union countries started to suspend the rollout of the AstraZeneca vaccine, citing concerns about it being linked to reports of blood clots in people who received the vaccine.

Denmark, Iceland and Norway were first out of the blocks, closely followed by Italy and Austria and a number of other EU countries. The Italian suspension was said to be a precautionary measure following the deaths of two Italians after receiving the vaccine, and Denmark also said their action was purely precautionary while an investigation took place into reports of blood clots in people who received the vaccine and the death of one person who had recently been vaccinated. Austria decided to suspend the vaccine after a woman died from ‘blood coagulation problems’ more than a week after being vaccinated from one of a particular batch of a million doses sent to EU countries.


France and Germany have also halted the AstraZeneca vaccine to study the data in more detail.

Whilst at first glance this may appear a concerning development, when you start looking at figures for thromboembolic (clotting) events then some perspective begins to appear, which is one of the reasons why health officials both in the UK and Europe have been quick to confirm the continuing safety of the AstraZeneca vaccine.

The World Health Organisation said the vaccine should continue to be used and in this country, the MHRA stated there was no evidence the vaccine had caused this problem, that blood clots are common and occur naturally, and that more than 11 million doses of the Covid-19 vaccine have been given so far in the UK with very few cases of severe side effects.

The EMA – the EU’s medicine regulatory body – said there was no indication that the vaccine was linked to an increased risk of blood clots. It then went on to say that the benefits of the vaccine outweighed any potential risks and that it could continue to be rolled out whilst investigation into cases of blood clots were ongoing.

The key here – and the reason why I and my medical colleagues am continuing to recommend the vaccine – is that blood clots are a routine but rare occurrence in medicine. Every year in the UK, one in a thousand people suffer from a venous thromboembolism (a blood clot, usually in the calf or lung) or one thousand per million annually. So far, just over 30 cases of thromboembolic events have been reported among around five million people given the AstraZeneca vaccine in the EU. As it stands there is a higher chance of you developing a blood clot without having had the vaccine.

In the Oxford AstraZeneca vaccine trials, which allowed for its licence to be approved, 38 per cent of participants reported some degree of adverse effect, however mild, and interestingly so did 28 per cent of those who had been given a dummy vaccine. Less than 1 per cent reported any type of serious adverse event, and the majority of those had also been given the placebo vaccine. This therefore appears to be a remarkably well-tolerated vaccine.

It is a medical truism that nature continues to inflict common causes of illness and death on us irrespective – and separate to – the pandemic , so the greater the numbers of people that are vaccinated, the more likely it is that some of the vaccinated experience an unrelated common event such as a blood clot, stroke or heart attack. These are common events in general practice seen on a daily basis prior to the vaccine roll out. Although any vaccine carries the risk of a potential side effect for a small number of people, these are almost always mild, with severe side effects being very uncommon.

The advice here therefore remains to have a Covid-19 vaccine when called for one, including the Oxford AstraZeneca jab.

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