Thursday, October 21, 2021

AstraZeneca Covid vaccine: weighing up the risks and rewards

Vaccines have side-effects, as do all medicines. Most often, jabs cause sore arms, a headache or a bit of nausea – none of which would be very significant when weighed against the toll of a serious virus such as Covid-19.

But sometimes the risk-benefit calculation may look less simple, as in the case of Oxford/AstraZeneca’s Covid jab and cerebral venous sinus thrombosis (CVST), the blood clots in the brain that have led to fatalities in the UK and Europe.

Doctors, scientists and regulatory bodies all urge that people should continue to have the AstraZeneca vaccine, which has been shown to be safe and effective in millions of people. In the UK, more than 18 million have had it. Among those, there have now been 22 cases of CVST and eight others where – as in CVST – blood clots develop in association with low platelets in the blood. It’s a very rare condition, which has also been seen occasionally with the blood-thinning drug heparin. Seven people have died.

There is no doubt that people at high risk for Covid should take any vaccine they can get. But it now seems that the reports of blood clots are mostly from a specific group who might not all be at high risk from Covid – younger women.

The first cases to come to light triggered a panic, leading to some European countries suspending the AstraZeneca jab for everyone, which may have proved to be something of an own goal. France and Germany were soon lamenting their poor vaccine coverage, which left millions at risk of disease and death from Covid.

Meanwhile the UK took the opposite attitude. The Medicines and Healthcare products Regulatory Authority (MHRA) initially appeared to dismiss the concerns. On 16 March, its vaccines safety lead, Dr Phil Bryan, said: “We are closely reviewing reports, but the evidence available does not suggest the vaccine is the cause. Blood clots can occur naturally and are not uncommon … the number of blood clots reported after having the vaccine is not greater than the number that would have occurred naturally in the vaccinated population.”

Two days and a review later, that statement was replaced on the MHRA website with an acknowledgment that cases of rare blood clots (five at that time) had occurred in the UK. “Given the extremely rare rate of occurrence of these CVST events among the 11 million people vaccinated, and as a link to the vaccine is unproven, the benefits of the vaccine in preventing Covid-19, with its associated risk of hospitalisation and death, continue to outweigh the risks of potential side-effects,” said its chief executive, Dr June Raine. On Tuesday, a trial of the AstraZeneca vaccine on children was paused while MHRA investigations continue.

The World Health Organization and the European Medicines Agency agree that there is an overwhelming argument for using the AstraZeneca jab. But nobody is dismissing the reports now. They and the MHRA are now figuring out whether there are ways to identify and protect those more likely to suffer blood clots.

Urgent investigations will be taking place into any common factors among the cases: whether they had an underlying health condition, for example, or were on medication of some sort. And doctors have already been alerted to the symptoms of CVST – the main ones are headache, blurred vision and fainting – in the hope of picking them up early and treating them before people become severely ill. That way, it is hoped, the risk-benefit calculation can again become much easier.

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