Oxford/AstraZeneca vaccine and blood clots: Should we be worried?

A number of countries in Europe and across the world have suspended use of the Oxford/AstraZeneca coronavirus vaccine. It comes amid reports of a small number of people developing blood clots after having the jab.

Here we take a look at the key questions surrounding the situation.

What has happened?

There have been a small number of reports of people experiencing blood clots in the days and weeks after receiving the Oxford vaccine.

The European Medicines Agency (EMA) reported one person in Austria was diagnosed with blood clots and died 10 days after vaccination, but it stressed there is “currently no indication that vaccination has caused these conditions”.

The World Health Organisation (WHO), the EMA and the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) said there was no evidence of a link between the vaccine and an increased risk of blood clots.

Which countries have suspended rollout?

On Monday 15 March, Italy, France and Germany said they would be suspending distribution of the jab, joining the Republic of Ireland, Denmark, Norway, Bulgaria, Iceland and Thailand.

French president Emmanuel Macron said the country was making the move as a precaution.

What do the regulators say?

The EMA has again insisted the benefits of the Oxford/AstraZeneca COVID-19 vaccine outweigh the potential side effects.

It said events involving blood clots, some with unusual features such as low numbers of platelets, have occurred in a very small number of people who received the vaccine, but that thousands of people develop blood clots annually in the European Union for different reasons.

The MHRA said that more than 11 million doses of the AstraZeneca vaccine had been administered across the UK with no issues.

The International Society on Thrombosis and Haemostasis (ISTH) recommended that all eligible adults continue to receive their COVID-19 vaccinations.

What happens next?

The EMA’s safety committee (PRAC) will further review the information on Tuesday and has called an extraordinary meeting on Thursday to conclude on the information gathered and any further action that may need to be taken.

If the committee does find an association between the vaccine and blood clots, they will likely attempt to understand the mechanism, so as to avoid similar problems in the future.

Are UK scientists worried?

No. Scientists in the UK say there is no data to directly link the vaccine and the blood clots.

Dr Michael Head, senior research fellow in global health, University of Southampton, said the decisions to halt the rollout “look baffling”.

“The data we have suggests that numbers of adverse events related to blood clots are the same (and possibly, in fact lower) in vaccinated groups compared to unvaccinated populations,” he said.

“Halting a vaccine roll out during a pandemic has consequences. This results in delays in protecting people, and the potential for increased vaccine hesitancy, as a result of people who have seen the headlines and understandably become concerned. There are no signs yet of any data that really justify these decisions.”

Dr Stephen Griffin, associate professor in the school of medicine, University of Leeds, said nationwide gestures such as this are bound to fuel hesitancy, or more extreme anti-vaccine sentiment, further undermining the vaccination effort.

“Whilst it is right that any possible links between serious adverse reactions to a vaccines are investigated, it is important to establish the likelihood of causation, as opposed to association, when doing so,” he said.

Does it make a difference who has been getting the vaccine?

Griffin says that the patients who have been vaccinated so far are more likely to have unrelated blood clotting.

“It is likely that the early stages of the European rollout have primarily comprised elderly and more clinically vulnerable patients, which might be expected to have a much higher incidence of random clotting-related events,” he said.

What has AstraZeneca said?

AstraZeneca also said its own review had found no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country.

In clinical trials for the jab, the number of clotting incidents was small and “lower in the vaccinated group” than in those who were unvaccinated, it added.

Read more about coronavirus vaccines:

• Two doses of COVID vaccine offers similar protection to previous infection, study finds
• Pfizer vaccine may be effective against all coronavirus variants

from... sciencefocus.com