Damned if you don't
Despite increasing numbers of blood clot cases, the Oxford/ AstraZeneca and Johnson & Johnson vaccines remain important
Over the last week, there have been further cases of blood clots associated with Covid-19 vaccines. For the Oxford/ AstraZeneca vaccine, the number of cases has reached 168, with 32 fatalities. The age range for people affected by the clots was 18-93 and more women than men were affected (93 women and 75 men). The numbers are starting to sound frightening, although they are still dwarfed by the numbers of Covid-19 cases and deaths. In Britain in the last week, there were more than 17,000 new Covid-19 cases and 162 deaths, in a country which has been in some level of lockdown for months and still has tight restrictions in place limiting who can meet and which businesses can open.
There have also been further cases of blood clots associated with the Johnson & Johnson vaccine in the USA. In last week’s article, I mentioned 6 confirmed cases. That number is now 15, all women.
There has also been one report, from Australia, of someone developing a blood clot after receiving the Pfizer/ BioNTech vaccine. However, the information released about this case hasn’t stated the type of clot, nor whether the clot was associated with the unusual symptom of low blood platelets, which has been seen in the cases associated with the other vaccines. In addition, the person affected had a previous history of blood clots. In this case, it would be premature to link this vaccine with blood clots. The US Centres for Disease Control indicate that there have been no blood clots linked to the Pfizer/ BioNTech vaccine in the USA, with nearly 100 million doses administered.
That evidence is good news for New Zealand, which is relying on the Pfizer/ BioNTech vaccine. But it’s worrying news for the rest of the world, and for vaccine development in general. Why are two vaccines, and only those two vaccines, causing rare blood clots at the same time as dangerously low levels of blood platelets? And are there risk factors which predispose certain people to getting the clots?
The answers to those questions are still uncertain, but we do know more now than we did a week ago. There’s a great article in The Atlantic which explains a number of different theories for how the vaccines could be contributing to clots. It’s far from clear which could be correct at this stage, though. Risk factors, too, are uncertain. In an article in New Scientist, Professor Andreas Greinacher, who has studied the clots, says that he thinks there must be some common factor with the people who were affected, otherwise the clots would be much more common. But there’s still no evidence of what that common factor could be.
Despite this mounting evidence about blood clots, the vaccines remain an important part of the battle against Covid-19 around the world. The US has now resumed use of the Johnson & Johnson vaccine. Europe has also started using it. Most European countries have also resumed use of the Oxford/ AstraZeneca vaccine, although Denmark has suspended its use indefinitely. Canada, which had previously recommended the Oxford/ AstraZeneca vaccine only for those aged 55 and over, is now recommending it for those aged 30 and over. Australia, which has had six cases of blood clots linked to the Oxford/ AstraZeneca vaccine, continues to use it. So does Britain, and so do many other countries.
Although the evidence is mounting up that these two vaccines cause dangerous blood clots, it’s also becoming increasingly clear that the threat from Covid-19 is far from over. The situation in some parts of India is particularly horrifying, with more than 330,000 cases and over 2000 deaths in the last 24 hours. New variants continue to emerge – the P1 variant that emerged in Brazil is now spreading rapidly through South America. Covid-19 remains a dangerous and frightening disease, and for most governments and many people, the vaccines are still worth the risk.
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