- Thailand on Friday became the first Asian country to halt the use of the jab over safety concerns, shortly after Denmark announced a two-week pause to its nationwide rollout after reports of blood clots and one death.
- Europe's drug regulator, the European Medicines Agency, stressed on Thursday that there was no indication the shot was causing blood clots, adding it believes the vaccine's benefits "continue to outweigh its risks."
- AstraZeneca has said the vaccine has been studied extensively during Phase 3 trials and peer-reviewed data confirms the shot is "generally well tolerated."
LONDON — The coronavirus vaccine developed by AstraZeneca and the University of Oxford has now been suspended in a number of countries across Europe and Asia, following reports of blood clots in some vaccinated people.
Many other nations, however, have defended their use of the shot and said they will continue their respective inoculation campaigns.
Thailand on Friday became the first Asian country to halt the use of the jab over safety concerns, shortly after Denmark announced a two-week pause to its nationwide rollout after reports of blood clots and one death.
In a setback to Europe's ailing vaccination campaign, seven other countries have also suspended the use of the Oxford-AstraZeneca shot: Norway, Iceland, Bulgaria, Luxembourg, Estonia, Lithuania, and Latvia.
Austria and Italy, meanwhile, have said that they will stop using certain batches of the vaccine as a precautionary measure.
Europe's drug regulator, the European Medicines Agency, stressed on Thursday that there was no indication the shot was causing blood clots, adding it believes the vaccine's benefits "continue to outweigh its risks."
The EMA acknowledged some member states had paused the use of the Oxford-AstraZeneca shot but said inoculations may continue to be administered while an investigation of blood clot cases is ongoing.
As of Wednesday, around 5 million people in Europe had received the Oxford-AstraZeneca vaccine. Of this figure, 30 cases of so-called "thromboembolic events" have been reported. These cases refer to blood clots forming in the blood vessels and blocking blood flow.
AstraZeneca has said the vaccine has been studied extensively during Phase 3 trials and peer-reviewed data confirms the shot is "generally well tolerated."
Why are countries pausing vaccination campaigns?
Thailand's health ministry on Friday announced it would temporarily postpone the use of the Oxford-AstraZeneca vaccine, reportedly describing the shot as a "good vaccine" but one it wishes to suspend for safety investigations.
Kiattiphum Wongjit, permanent secretary for the Public Health Ministry, said the Southeast Asian country was able to pause its vaccination campaign because it had largely brought a second wave of Covid cases under control through quarantines and border controls, according to Reuters.
The country of nearly 70 million people has so far recorded around 26,600 cases and 85 deaths, according to data compiled by Johns Hopkins University.
Thailand's decision to suspend its planned rollout of the Oxford-AstraZeneca vaccine, which had been due to begin on Friday, came after the decision by the Danish Health Authority.
"It is important to emphasize that we have not opted out of the AstraZeneca vaccine, but that we are putting it on hold," Soren Brostrom, director of the National Board of Health in Denmark, said on Thursday.
"There is good evidence that the vaccine is both safe and effective. But both we and the Danish Medicines Agency have to react to reports of possible serious side effects, both from Denmark and other European countries."
Many high-income countries have chosen to continue the rollout of the Oxford-AstraZeneca vaccine in the wake of safety concerns.
The U.K., France, Australia, Canada and Mexico are among some of the nations that have sought to reassure citizens about the benefits of getting the vaccine and have said they will continue their respective inoculation campaigns.
"An analysis of our safety data of more than 10 million records has shown no evidence of an increased risk of pulmonary embolism or deep vein thrombosis in any defined age group, gender, batch or in any particular country with COVID-19 Vaccine AstraZeneca," a spokesperson for AstraZeneca said.
"In fact, the observed number of these types of events are significantly lower in those vaccinated than what would be expected among the general population."
What do the experts say?
The EMA's safety committee is reviewing the issue, but has said there is currently no evidence the vaccination had caused blood clots — noting they are not listed as side effects of this vaccine.
Europe's drug regulator also noted that the data available so far showed that the number of blood clots in vaccinated people is no higher than that seen among the general population.
"Reports of blood clots received so far are not greater than the number that would have occurred naturally in the vaccinated population," said Dr. Phil Bryan, vaccines safety lead at Britain's Medicines and Healthcare Products Regulatory.
"The safety of the public will always come first. We are keeping this issue under close review but available evidence does not confirm that the vaccine is the cause. People should still go and get their COVID-19 vaccine when asked to do so," Bryan said.
Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, said: "The problem with spontaneous reports of suspected adverse reactions to a vaccine are the enormous difficulty of distinguishing a causal effect from a coincidence."
"This is especially true when we know that Covid-19 disease is very strongly associated with blood clotting and there have been hundreds if not many thousands of deaths caused by blood clotting as a result of Covid-19 disease. The first thing to do is to be absolutely certain that the clots did not have some other cause, including Covid-19," Evans added.
How does the vaccine work?
The Oxford-AstraZeneca vaccine is a shot designed to prevent the coronavirus in people aged 18 and older. It is made up of an adenovirus that has been modified to contain the gene for making a protein from SARS-CoV-2, the virus that causes Covid-19.
The most common side effects of the shot, which does not contain the virus and cannot cause Covid, are typically mild or moderate and improve within a few days of vaccination.
Late-stage clinical trials found the AstraZeneca-Oxford shot to have an average efficacy of 70% in protecting against the virus.
A more recent study by Oxford researchers found that the Covid vaccine was 76% effective at preventing symptomatic infection for three months after a single dose, and that the efficacy rate actually rose with a longer interval between the first and second doses.
— CNBC's Holly Ellyatt contributed to this report.