28 July 2021

Needless panic over the AstraZeneca vaccine has cost lives


The moral panic about AstraZeneca vaccines and blood clots has done immense damage. It has undoubtedly increased vaccine hesitancy which reduced uptake, not only in the United Kingdom, but also across Europe and as far-flung as Australia. The result is more cases, hospitalisations and deaths. The restriction of AstraZeneca for younger cohorts has also reduced personal autonomy.

A new study, out in preprint from The Lancet, provides a strong indication that all the fuss was unnecessary. The researchers investigated blood clots after vaccination with AstraZeneca and Pfizer among a million people in Catalonia over six months. Importantly, they compared this to the general rates of blood clotting in the population at large and compared it to the chance of blood clots from Covid-19 infection. This is one of few population-based studies assessing the incidence of blood clotting.

They found vaccinations do very slightly increase the risk of blood clots, albeit far less than infection from Covid-19. They considered three types of blood clots: venous thromboembolism (VTE), arterial thromboembolism (ATE) and thrombosis with thrombocytopenia syndrome (TTS). Strikingly, for all the focus on AstraZeneca, the researchers conclude that the safety profiles of the two vaccines are “broadly similar”.

Taken in turn, the risk of VTE is slightly higher for Pfizer (a 1.3-fold increase compared to the general population) compared to AstraZeneca (a 1.15-fold increase) after a first dose. By contrast, the risk of VTE increases 8-fold after diagnosis of Covid-19: 499 instances of VTE compared to 62 expected occurrences in the population. So in other words, if you’re really concerned about blood clotting you should get the vaccine rather than take your risk with Covid-19.

The risk of TTS is higher for AstraZeneca (a 3.52-fold increase) than for Pfizer (1.35-fold increase). ATE incidents were similar across both vaccinations to what would be expected across the population over that time period.

The good news is that the risk could be entirely eliminated in vaccine updates. University of Oxford and AstraZeneca researchers are attempting to identify the reason for the low rate of blood clots and update the vaccines to entirely remove the risk.

The Covid-19 vaccines represent a seminal moment in humanity’s fight against pestilence. After decades of research into ‘plug and go’ vaccines we saw how they can be adapted to a new viral threat, rapidly tested to demonstrate effectiveness and safety, and brought to market.

Regulators understood that the rewards from these life-saving vaccines far outweigh the risks. They have enabled the UK to remove legal restrictions despite tens of thousands of daily cases. The jabs have turned the virus into something we can manage using existing healthcare resources rather than something that must be suppressed or eliminated.

These technologies are now being adapted to other threats such as malaria – which has killed millions in recent decades. The challenge is to accelerate this process even faster by researching threats, preparing vaccines and ensuring ample advance manufacturing and logistical capacity.

Irrational concerns about very rare side effects cannot be allowed to get in the way of saving lives.

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Matthew Lesh is Research Director at the Adam Smith Institute.

Columns are the author's own opinion and do not necessarily reflect the views of CapX.