IN EUROPE, vaccination against covid-19 is off to a worryingly slow start. Just 11 doses for every 100 people have been administered in the European Union, against 32 in America and 38 in Britain. Europeans are cross with their governments and with the European Commission, which botched the ordering of vaccines for the EU last year. Worse, another wave of infections seems to be building in several countries.
But in recent days worries about speed have been joined by concerns about safety. On March 15th France, Germany and Italy became the latest in a growing list of European countries, now more than a dozen, to announce that they were temporarily halting the use of a covid-19 vaccine made by AstraZeneca, a British-Swedish pharmaceutical firm.
The wave of suspensions was set in motion by data from a Norwegian medical regulator that reported four cases of blood clotting in adults given the vaccine. Similar—and similarly small—reports have come from Denmark, Italy and Austria.
So, is the AZ vaccine safe to use?
Almost certainly, yes. Officials have been careful to describe the suspensions as temporary measures. Ronan Glynn, Ireland’s deputy chief medical officer, said there was no proof that the vaccine had caused the clots. The World Health Organisation and the European Medicines Agency (EMA) have likewise said they have no reason to believe the jab is unsafe.
The point at issue, as so often in medicine, is the disentangling of causation from correlation, especially when it comes to medicines given to millions of people. Blood clots are common. So, increasingly, are covid-19 vaccines. The EMA reckons there have been 30 “thromboembolic events” among around 5m people who have been given AstraZeneca’s vaccine. That some people with blood clots have also had a covid-19 vaccine is, by itself, no more remarkable than the fact that some of them will probably have taken vitamin supplements, or paracetamol, or breakfast. The question is whether the rates are higher than would otherwise be expected—which they do not seem to be. “The number of [blood clots] in vaccinated people is no higher than the number seen in the general population,” says the EMA.
Data from elsewhere are similarly reassuring. In the clinical trials used to assess the vaccine, 38% of those given the jab reported at least one side-effect, chiefly things like pain at the injection site, a headache or a transient fever. So did 28% of those in the group given a dummy injection. Less than 1% of either group went on to suffer any serious illness. Of those who did, more had been given the placebo jab than the real one.
Trial data are backed up by real-world experience in other countries. By February 28th Britain had administered 9.7m doses of the AstraZeneca vaccine and 11.5m doses of another vaccine, made by Pfizer, an American firm, in a partnership with BioNTech, a German one. The Medicines and Healthcare Regulatory Agency, Britain’s medicines regulator, reckons that both vaccines cause between three and six reports of side-effects for every 1,000 doses delivered, almost all of which are mild. Two hundred and twenty-seven people died shortly after receiving a dose of the Pfizer-BioNTech jab; 275 after the AstraZeneca one. Once again, neither figure seems unusual, and the deaths are unlikely to be linked to the vaccines. Around half a million people die in Britain every year, and the very old and very sick were first in line for jabs.
But there may be more to the question than matters of immunology. One factor is the politics of vaccines. In January AstraZeneca warned the EU that it would not be able to supply as much vaccine as it had hoped, sparking a bitter row that became enmeshed in a broader dispute about Britain’s relationship with the EU following Brexit (AstraZeneca vaccines are made in Britain, among other places). An article in a German newspaper, based on an anonymous source, raised doubts—later proved incorrect—about the vaccine’s effectiveness in people over 65. Those claims were later amplified by Emmanuel Macron, France’s president, who suggested the vaccine was “quasi-ineffective” in older people. (Mr Macron later changed his position, as France sought to accelerate its vaccination campaign).
Another problem is what experts call “vaccine hesitancy” in Europe. The controversies over the AstraZeneca vaccine may have sown doubt about it. That, in turn, may have made public-health officials especially keen to be seen to take safety concerns seriously. Experiences with other vaccines show that doubts, once instilled, can be hard to get rid of. The idea that the combined measles, mumps and rubella (MMR) vaccine causes autism was based on a single paper that reported a handful of anecdotal associations. The existence of such a link has now been comprehensively disproven. MMR conspiracy theories flourish nevertheless. Many rich countries vaccinate children against human papilloma virus (HPV), which causes cervical cancer. After anecdotal reports of side-effects in 2013, Japan suspended its HPV-vaccination programme. No amount of evidence for the safety of the HPV vaccine has managed to reinstate it. One paper estimates that the result has been the deaths of between 5,000 and 5,700 Japanese women born between 1994 and 2007.
Having scrambled to secure the AstraZeneca vaccine in January, large parts of Europe are now left with stockpiles that are not being used. Public-health officials, meanwhile, are caught in a bind. If people already harbour doubts about a vaccine, a temporary pause may be seen as a reassuring commitment to rigour and caution. Or it may simply add to those doubts, causing more people to shun the vaccine, prolonging the pandemic and killing some who would otherwise have lived. One of the “adverse effects” of covid-19, after all, is death. It occurs in just under 1% of cases.