Unforeseen safety issues routinely arise after new drugs or vaccines move from testing on tens of thousands of volunteers to actual public use on tens of thousands of volunteers. So it came as no great surprise that an extremely small percentage of people developed a strange blood clotting problem after receiving either the Johnson & Johnson (J&J) COVID-19 vaccine or the AstraZeneca vaccine, widely used outside of the US
Rare but dangerous side effects of vaccines can pose a delicate dilemma for health officials. In this case, the life-threatening blood clots, accompanied by an oddly low number of coagulant platelets, appear to affect about two people per million people who have been vaccinated with J & J’s shot and about one per 100,000 people who receive AstraZenecas. Both are tiny risks compared to COVID-19 itself, which is estimated to kill around two in 1,000 infected people (although death rates vary widely based on age, location, and other factors). On the one hand, it is important to be transparent to the public – and to make healthcare providers aware of the problem and advise them on how best to identify and treat it. On the other hand, there is a possibility of sowing unwarranted doubts about these vaccines, and perhaps others too, which is already creating worrying hesitation about vaccines.
“The moment you told people there was a risk, even if it’s one in a million, I think they’ll hear that this can happen to me,” says pediatrician and vaccine researcher Paul Offit, Director of the Vaccination Education Center at Philadelphia Children’s Hospital.
The discovery of the coagulation problems – in early March for AstraZeneca and in early April for J&J – led to emergency meetings of health officials in the US and Europe and disruptions in the distribution of both vaccines in countries around the world. However, by April 23, health officials in both regions concluded that the benefits of these vaccines far outweighed the risks and that the proliferation should resume, although new labels warn of the very rare blood clots.
Whether the breaks were justified is controversial as a deadly global pandemic urgently needs to be stopped. When asked about pure mathematics, experts say the answer is clearly no. “Of a theoretical million people who receive this vaccine,” says Offit, only a few will suffer from the peculiar clots. “But out of a theoretical million people who get COVID, thousands will die.”
One of the toughest questions for health officials is a psychological one: To what extent can the public have a practical understanding of a very rare – but very frightening – potential side effect? “Most people are illiterate at risk,” says psychologist Gerd Gigerenzer, director of the Harding Center for Risk Literacy at the University of Potsdam. “A large number of studies show that ordinary people are confused by relative risks, opportunities, or proportions.” Research shows that we can overestimate the likelihood of a rare event, especially if it is new and deadly and has been amplified by the news media, says psychologist Baruch Fischhoff, professor of engineering and public order at Carnegie Mellon University and an authority on communications Health risks.
Both Fischhoff and Gigerenzer believe health officials can help prevent such confusion by providing the public with very clear, well-worded information – something Fischhoff said could do much better for US and European health officials. “Most people have no problem understanding the risk if you, as an expert, do your job right,” he says. “Give math a chance!”
The coagulation problem was filtered out for the first time in late February in connection with the AstraZeneca vaccine, which has not yet been approved in the US. As of March 22, the European Medicines Agency (EMA) was aware of 86 cases in Europe, 18 of which were fatal and the UK – an extremely small number compared to the 25 million people who had received the vaccine at the time. The cases focused on women under the age of 60.
This month, U.S. health officials received reports of similar cases related to the J&J injection, a single-dose vaccine given to about eight million people in the country. At least 15 coagulation cases have been reported, all in women under the age of 60, and at least three were fatal.
In Europe, AstraZeneca’s findings sparked a patchwork response. More than 20 countries have stopped distributing this vaccine for a week or more. Most were resumed with a series of new recommendations that the vaccine should only be used in adults over the age of 55, 60 or 65 – or in the case of the UK, adults under 30 should opt for other vaccines. However, the EMA has not endorsed age restrictions, nor has it stated that younger women should avoid choosing AstraZeneca – positions that have been reflected by US authorities regarding the J&J vaccine.
In the US, the J&J break lasted 10 days. Executives from the Centers for Disease Control and Prevention and the Food and Drug Administration said they needed time to investigate blood clot cases and acted “out of caution.”
That phrase didn’t go well with a number of health communication experts. “It sounds like there’s no downside [to the pause]although there can actually be a significant downside, ”says Glen Nowak, director of the Center for Health and Risk Communication at the University of Georgia and former chief of vaccine communication at the CDC. One of the biggest concerns was the impact of losing the easy-to-carry J&J vaccine in a dose intended for use in rural communities, the homeless and other hard-to-reach groups. “We used the J&J vaccine on vulnerable and transient populations where people may not be able to get a second dose,” Nowak says.
In order for the public to understand such decisions, Fischhoff said health officials need to use certain numbers to explain whether taking a break is likely to injure fewer people than without – an estimate they can reasonably make, although they can reasonably get it on the spot Vary location. They should also explain how confident they are about their information. In his opinion, the first explanations for the vaccination breaks were “a colossal communication error”. At the time of publication, the CDC has not responded Scientific AmericanPlease comment.
Both the CDC and EMA have released some information on relative harm. At a virtual media event on April 23, CDC Director Rochelle P. Walensky stated that every million doses of J&J vaccine given to women aged 18 to 49 would prevent 650 hospitalizations and 12 deaths from COVID, while this would cause about seven cases of blood clots. The EMA has gone further: it has released a detailed (if somewhat daunting) series of infographics comparing such statistics for the AstraZeneca vaccine and breaking it down by age and prevalence of the coronavirus. For example, in high-frequency locations, a million doses of the vaccine given to adults in their thirties would prevent 81 hospitalizations for COVID and could include 1.8 cases of clotting. For people in their 80s, an estimated 1,239 hospitalizations and 0.4 coagulation cases were prevented.
Can most people follow this type of math? Gigerenzer’s work has shown that presenting information in simple tabular form – what he and his staff refer to as “fact boxes” – can help people more easily weigh risks against the benefits of vaccines and other health measures. Well-designed infographics that visually represent the relative risk, such as those created by the Winton Center for Risk and Evidence Communication at Cambridge University and which were the models for the EMA charts, also help. In the long run, Gigerenzer believes that much more can be done to educate the public from childhood on about thinking about risk and probability. And he notes that there is one more lesson that would help people understand what a one-in-a-million side effect means: We have to learn that almost nothing is risk-free.
At the press conference on April 23, the CDC’s Walensky recognized the urgent need for good communication to assess the benefits and risks of vaccines. “We need to make extraordinary connections with patients, meet people where they are, to educate them,” she said.
The final impact of the breaks and the uneven messaging of the side effects remains to be seen. But there is cause for concern, says Heidi J. Larson, director of the Vaccine Confidence Project, a research organization that tracks global views on vaccines. In the weeks after European nations stopped using the AstraZeneca vaccine, she said, “We have seen a steep decline in vaccine confidence in Africa” - where that shot was expected to be the mainstay. A Washington Post–ABC News poll, conducted during the J&J hiatus, suggests similar damage was being done in the US: Only 22 percent of unvaccinated Americans said they would be willing to give the J&J shot do. Larson and others fear that confused and concerned people often fall back on unreliable sources of vaccination security. “If they don’t get clear answers,” says Larson, “the door to misinformation and disinformation remains wide open.” People fill this space with their own action. “
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