By Liliana Shymanska, Corporate Communications Officer at the British Science Association


There has been a lot of conversation recently about the Oxford-AstraZeneca vaccine and blood clots, but what does this mean for ‘vaccine hesitancy’?

In the past fortnight, over a dozen European counties halted the use of the Oxford-AstraZeneca vaccine following reports of an association with blood clots. Following a review, the rollout started again – almost as quickly as it was halted. This delay was short-lived, but it’s likely that the consequences won’t be.

The stop-start vaccine rollout, partnered with misinformation across Europe, may have dented (an already low) confidence in the Oxford-AstraZeneca vaccine - or COVID-19 vaccines altogether.

Meanwhile, in the United States, there’s been another fresh setback for the AstraZeneca vaccine, as a US health agency questioned the data from the large-scale vaccine trial in the United States.

All this debate shares a common root – our understanding of data and risk. What is safe to do during the pandemic? What isn’t safe? What do these numbers mean? Is this information reliable? It’s human nature to spot patterns in data but it’s important to remember, correlation doesn’t necessarily mean causation.

Vaccinations aside, blood clots happen every day. If you vaccinate lots of people, it’s inevitable that some of the population who would have a blood clot are going to overlap. As of today (24 March 2021), according to the European Medicines Agency, the AstraZeneca vaccine is not associated with an increased overall risk of blood clotting. The numbers actually suggest the incidence of a blood clot among the vaccinated population to be lower than the general population.

So, if the number of blood clots are lower than would be expected, why did so many countries halt the use of the vaccine?

Well, that’s a complicated question to answer, but in most instances, the decision was made as a precaution to avoid potential harm. The logic being, if there is even a tiny risk that the vaccine was causing an increased chance of developing a blood clot, then halting the rollout of the vaccine eliminates that risk. However, the resulting increase in vaccine hesitancy caused by this decision has almost certainly led to a greater risk for the public – further exposure to COVID-19.

Anxiety around possible side effects for any new vaccine or treatment is understandable. Especially given the apparent speed with which COVID-19 and the subsequent vaccines came into our lives. Keeping track of reported side effects is crucial – yes. But not all adverse effects will be caused by the vaccine itself.

A recent study conducted by YouGov revealed that 61% of those surveyed in France deemed the Oxford-AstraZeneca vaccine unsafe (somewhat or very unsafe). This number rose by 43% in just two weeks as a result of the news coverage of blood clots. Similarly, 55% of Germans surveyed think the Oxford-AstraZeneca vaccine is unsafe, up by 15% since the news story broke. A similar narrative can be seen in Spain (52% deem unsafe) and Italy (43% deem unsafe) too.

Graph courtesy of YouGov.

So, why does vaccine hesitancy matter?

Hesitancy could put Europe’s exit strategy from the pandemic at risk. And as much of Europe heads into a third wave, it’s clear to see how devastating this setback could be.

Here in the UK, vaccine hesitancy is low. The blood clot concerns had little impact, with 77% of the population still considering the vaccine safe according to YouGov. This week, The Office for National Statistics reported that 94% of adults have now either received, are awaiting or are likely to take the vaccine if offered.

Despite this, the data also identifies certain sub-groups of the population that tend to be more vaccine hesitant. Among these subgroups are some minority ethnic communities and those living in more deprived areas.

This is important to note as it’s not just about how many people are vaccinated – but who is vaccinated, that also matters.

If those who are unvaccinated are evenly distributed throughout the population, outbreaks can be kept at bay as contact between anyone who is infected with COVID-19 and those who are vulnerable to contract it is limited. But if those who aren’t vaccinated are in closer proximity to each other, local outbreaks could keep cropping up where lots of people remain unprotected.

Although unlike much of Europe, vaccine hesitancy remains low in the UK, the possibility of local outbreaks is concerning. This is especially true when paired with the knowledge that some of the most hesitant communities are those who have suffered disproportionately during the pandemic.

If false alarms continue to arise, a subsequent increase in vaccine hesitancy could mean COVID-19 risks exacerbating existing inequalities.

Navigating constant risk assessments over the past year has been frustrating but it’s crucial to continue in preventing the spread of misinformation and taking the time to verify what you see. If you’re interested in finding out more about COVID-19 vaccines, visit these credible sources:

Check out our blog post titled ‘From pandemic to infodemic’ which includes more verified sources on COVID-19 and how to tackle misinformation.