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Vaccine puzzle gets more complicated as blood clots are considered

But the risk is minuscule

By Ricky Browne

The issue of whether or not the Oxford AstraZeneca vaccines causes blood clots in some very rare cases came to the fore today in both the United Kingdom and the European Union – with concurrent and unconnected news conferences in London by British health officials and in Amsterdam by the European Medicines Agency (EMA).

In a nutshell, millions of people have received the Oxford AstraZeneca vaccine, but only a handful of people have suffered from blood clots. Both the UK and EU agencies believe that the benefits of the vaccine vastly outweigh the risks.


In the UK, about 20 million people have got the Oxford AZ vaccine – and 79 of those have got a blood clot with 19 people dying from a blood clot after receiving it.

That works out to a risk of about four people in a million vaccine recipients getting  a blood clot – considered a “very rare” incident.

Its just as likely that an airplane will hit your home

To put that in perspective, that risk of one in 250,000 is about equal to the risk of being hit in your home by a crashing airplane, according to stats from the BMJ.

Higher risks, according to the BMJ include: dying in a road traffic accident over 50 years of driving – 1 in 85, needing emergency treatment in the next year from injury by a can, glass bottle or jar – 1 in 1,000, needing emergency treatment in the next year from injury by a bed, mattress or pillow – 1 in 2,000, dying in any accident at home in the next year – 1 in 7,100 and drowning in the bath in the next year – 1 in 685,000.

And the risk of actually dying from a blood clot after getting an Oxford AZ vaccine is even lower – about 19 out of 20 million people – or about 1 in a million.

More than 20 million Oxford AstraZeneca jabs have been given in the UK

At the rate of one in 250,000, you are twice as likely to be hit by a bolt of lightening in the US. The risk of being hit by lightning in the US is about 1 in 500,000 according to the CDC. If that is something that concerns you, you are safer in the UK, where the risk of being hit by lightening is about 1 in 1.2 million.

But, as small as the risk may be, out of an abundance of caution, both the UK and EU health agencies have issued new guidelines on the Oxford AZ vaccine.


Over in the UK, the regulators have investigated the blood clots and has said that people under the age of 30 years should receive the Pfizer or Moderna vaccines.

Professor Jonathan Van-Tam deputy chief medical officer started his news conference just after the Amsterdam conference.

VAN-TAM… the UK vaccine programme has been a most enormous success

“The UK vaccine programme has been a most enormous success” Van-Tam said, as he kicked off the news conference.

Over 20 million AZ vaccines have been given in the UK. Very rare events only come out after mass use, and not in the much smaller trials – which is why these events are being seen now.

The MHRA says the benefits of the AZ vaccine, “continues to outweigh the risks”. The risk of blood clot remains “extremely small”.

In the UK there have been 79 cases, 51 of them women and 28 men. Out of those people, 19 people died up to March 31 – three of those were under the age of 30.

So in Britain, under new guidelines, people under the age of 30 should now receive a Pfizer or Moderna vaccine instead of the Oxford AZ. The Moderna vaccine became the third vaccine to be available in the UK today.

Putting the numbers in context, the risk of clots is much higher in the Covid-19 disease itself than with the vaccine. About 7.8 percent of people who have the disease get a blood clot, as do about 23 percent of those who are in intensive care.

So if you are worried about your chances of getting a blood clot, you are still better off getting an Oxford AZ vaccine.

But there is new advice for some people, including pregnant women, to consider higher risk.


Over in Amsterdam the EMA stated that vaccination is “extremely important” in fighting Covid-19.

“The benefits of the AstraZeneca vaccine outweighs the risk. It is a highly effective vaccine and it is saving lives” an EU health official stated at the conference.

The EMA said that blood clots should be seen as a “possible side effects of the vaccine” – although a rare event.

An immune response to the vaccine could be the reason for the rare blood clots, the EMA said.

But the words “very rare and unusual” were used several times during the conference to describe the incidents of blood clots, which the EMA said could not be narrowed down by age or sex – so there were no specific risk factors that can be identified.

The EMA couldn’t offer any recommendations to reduce the occurrence of the incidents, but spoke on looking out for signs of blood clots.


The new findings and recommendations may cause some people to have greater doubts about the Oxford AZ vaccine – particularly those who were already in doubt. The emphasis on how low the risk is – as little as four in one million (or 1 in 250,000) – may not be of much comfort to many, especially younger people. That compares to the risk of being hit by lightning which is about one in 500,000 in the UK.

Which one?

But the new restrictions on younger people will alarm many people, the world over, even though the risk of blood clot is tiny.

Some developing countries such as Jamaica in the Caribbean only have the Oxford AZ vaccine on offer, meaning another vaccine can not always be offered for young people.

In Jamaica the take-up of vaccines appears to be low, as many people who are of the right age have not shown up for their vaccines.

Today’s announcement by two sets of health authorities that there is a very small risk of getting a blood clot from the vaccine, and an even smaller risk of dying from that blood clot is likely to be blown up our of all proportion by many people who are already doubtful about the sense of taking any vaccine.

Many people may now try to hold off for another vaccine, or decide that they are better off not taking one at all — thereby multiplying their risk of dying from the Covid-19 disease.

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