The covid-19 vaccine jointly developed by AstraZeneca and Oxford University is once again running into trouble. On Monday, Germany, France, and Italy became the latest countries to suspend their rollout of the vaccine over concerns that it may increase the risk of blood clots. However, many experts and regulators say these suspensions are unwarranted and that the current data available does not point to an added danger of blood clotting from the vaccine.
The latest issue began early last week. Health officials in Austria suspended the rollout of the vaccine as a “precaution” on March 7, following the reports of two women in their 30s and 40s who developed clot-related health problems soon after receiving their doses, which had come from the same batch. One of these women subsequently died from her injuries. Austria’s regulatory agency (The Federal Office for Safety in Health Care) cautioned that there was no evidence of a causative link between the vaccine shots and these reports.
Soon after, Denmark, Norway, and Iceland followed suit with their own pauses of the vaccine. Denmark in particular suspended its rollout of the vaccine after a report of blood clot and death involving a 60-year-old woman who had received a dose from the same batch as the two women in Austria.
The decision to momentarily pull the AstraZeneca/Oxford vaccine by these countries comes with some important context. Last fall, the first results from the Phase III trials of the two-dose adenovirus-based vaccine were made public. The results indicated that people given one-and-a-half doses of the vaccine had higher levels of protection against covid-19 (around 90% efficacy) than those given two full doses (around 62% efficacy). However, the makers of the vaccine admitted a week later that they didn’t plan to test out the vaccine that way, and it was an error that led to some people receiving the half doses. The researchers were allowed by a panel of experts monitoring the research to keep it going in spite of the mistake.
At the time, many outside experts criticized AstraZeneca/Oxford for not disclosing the error right away and presenting possibly flawed data. The mishap was preceded by an earlier stumble in late summer—the temporary suspension of several trials after a report of brain injury possibly related to the vaccine. Though most countries restarted their trials soon after, the U.S. didn’t start them back up for seven weeks, reportedly because officials feared that AstraZeneca wasn’t being transparent enough about the reports.
Even though the UK and other countries approved the vaccine for emergency use starting in late December, there have continued to be lingering questions and bouts of bad luck during its deployment. The researchers behind the vaccine now argue that delayed doses, given three months apart, are actually more likely to improve its effectiveness, rather than smaller doses. In early February, South Africa canceled its rollout of the vaccine just before it began, after early data showed that it was minimally effective against B.135, a variant of the virus that emerged in the country last year (data from other vaccines has shown some diminished protection against B.135, but not to the extent of being useless).
Other setbacks haven’t been the fault of the vaccine makers at all; a German newspaper was criticized by many scientists in February after it published ultimately unfounded speculation that the vaccine was ineffective in older people.
Importantly, the AstraZeneca/Oxford vaccine does appear to be broadly safe and effective in preventing illness from covid-19—though exactly how effective is still unclear. Like the other vaccines available to the public, it also seems to cut the risk of transmission. And despite these latest reports, there also doesn’t seem to be a true increased risk of blood clotting.
Over the weekend, the UK’s Medicines and Healthcare products Regulatory Agency stated that there was no evidence of a blood clot risk linked to the vaccine and that people should still take the vaccine if provided to them. The World Health Organization chimed in as well last Friday, stating the same. And while the EU’s medical regulator—the European Medicines Agency—is still investigating these reports, it went out of its way on Monday to state that “the benefits of the AstraZeneca vaccine in preventing COVID-19, with its associated risk of hospitalization and death, outweigh the risks of side effects” at this time.
All drugs and vaccines come with side effects. But some health problems that show up after taking a treatment are only coincidence and not actually due to the treatment itself. One way to figure out whether any particular problem is related to the treatment is to look at how often it would be expected to show up in the general public during any given time period. And so far, according to data collected from millions of people in Europe, there doesn’t seem to be any higher risk of clotting in people who have taken the vaccine, compared to those who haven’t (if anything, the risk may be lower in vaccinated people, but that’s also likely just coincidental).
It’s worth wondering whether the earlier missteps by AstraZeneca/Oxford influenced the recent decisions to suspend vaccine rollout in several countries. But even if these pauses are understandable and turn out to be only temporary, they may come with a real cost.
Much of Europe, in contrast to the U.S., is the middle of a resurgence of covid-19, led by the spread of more transmissible and deadlier variants. One likely reason for the spikes is a lagging vaccination campaign in these countries—one that won’t be helped by the suspension of the AstraZeneca/Oxford vaccine. Many poorer countries are also expected to rely heavily on this shot for their rollout, given its relatively cheaper cost and easier storage compared to other vaccines. Meanwhile, the U.S. is sitting on tens of millions of unused doses as the local trial winds to an end—doses that the country may or may not loan out to others.
The whole situation is a complete mess, and no one comes out better for it—especially not the people who will die from covid-19 because they couldn’t get the AstraZeneca vaccine during these suspensions.