Europe’s drug regulator, the European Medicines Agency, on Tuesday said it had found a possible link between the J&J vaccine and rare blood clotting issues in adults who had received the jab in the US, Reuters reported. However, it also reiterated that the benefits of the J&J vaccine outweighed the risks.

US pandemic adviser Anthony Fauci said on Sunday he believed the US would resume use of the J&J jab, possibly with some restrictions or warnings.

02:01

China considers mixing Covid-19 vaccine types to boost effectiveness

China considers mixing Covid-19 vaccine types to boost effectiveness

Experts said health authorities had faced an impossibly complex and high-stakes calculation, amid ongoing efforts to launch mass vaccinations.

The big question: could limiting the use of vaccines that pose minuscule safety risks do more harm than good by extending the duration of the pandemic?

Why mRNA Covid-19 vaccines are our best long-term strategy

The responses by authorities have provoked disagreement among public health experts and fuelled discussion about how governments and populations alike perceive risk.

“Overall, the way we are responding to these vaccines and these very rare side effects, I think in the long run, will do more harm than good, will make the pandemic go on longer,” said Ashish Jha, dean of the Brown University School of Public Health in Providence, Rhode Island.

“It’s been pretty clear that regulators have thought a lot about the risk, but not about the risk of stopping, and not about the risk of pausing, and I think that’s a huge problem.” 

By all accounts, the risks posed by the vaccines are statistically minuscule.

The risk of a fatal reaction to the J&J shot is less than one in 7 million, based on reports of blood clots in six women in the US that left one woman dead and another in critical condition.

By comparison, the chances of being hit by lightning in a given year is approximately one in 500,000, according to the US Centers for Disease Control and Prevention.

OVERREACTION?

Blood clots are themselves a potential side effect of contracting Covid-19, with one non-peer reviewed study by the University of Oxford estimating the risk of cerebral blood clots from the disease to be 10 times greater than the risk posed by vaccines.

Concern about an overreaction to the risks is twofold: not only are restrictions likely to slow down the roll-out of vaccines, especially in countries with limited access to alternative jabs, they could potentially fuel broader public distrust of vaccination.

In Australia, a recommendation by health authorities that people under 50 get an alternative to AstraZeneca has prompted the government to abandon its target of administering at least one dose of vaccine to the entire population by October. Australian Prime Minister Scott Morrison on Monday announced plans to vaccinate most people under 50 using the Pfizer and Novavax shots, supplies of which aren’t expected to be delivered for months, during the last 12 weeks of the year.

In Hong Kong, authorities justified cancelling its order for 7.5 million doses of the AstraZeneca jab by pointing to existing supplies of the German-made BioNTech and Sinovac vaccines and the British-Swedish shot’s lower effectiveness against virus variants. Although supplies of the shots distributed by China’s Fosun Pharma and made by Beijing-based Sinovac are sufficient to cover the city’s population when combined, uptake of Sinovac has of late lagged far behind the BioNTech shot – raising uncertainty about the prospects for reaching herd immunity once supplies of the BioNtech vaccine are exhausted. 

06:18

SCMP Explains: What’s in a Covid-19 vaccine?

SCMP Explains: What’s in a Covid-19 vaccine?

Both the AstraZeneca and J&J jabs make up a large proportion of the vaccine supply held by Covax Facility, a global initiative established to ensure fair access to vaccines, making them crucial to efforts to inoculate the developing world. The vaccines are cheaper and easier to distribute and store than rivals such as the Pfizer jab, although they lack mRNA vaccines’ long-term advantage of being easily adaptable to deal with emerging virus variants.

Explained: Why more contagious Covid-19 variants are emerging

Owen Schaefer, an assistant professor at the Centre for Biomedical Ethics at the National University of Singapore’s Yong Loo Lin School of Medicine, said the calculation on limiting use of the vaccines varied based on the prevalence of disease.

“It depends on the context,” Schaefer said. “For places where Covid-19 is well-contained, like Hong Kong and Australia, this may make sense. Temporarily pausing distribution of a vaccine for a short period will have little adverse effect in places where few are suffering and dying of Covid-19.”

Schaefer said there was also an “asymmetry between causing harm and allowing harm to occur”.

“Arguably, we have much stronger duties to avoid causing harm than to prevent it,” he said, adding that such considerations could nevertheless not justify a pause in situations where the benefits of vaccination far outweigh the risks.

The effect on public trust in vaccines, a potentially much bigger concern, is harder to gauge.

Proponents of restrictions and advisories attached to the vaccines in recent weeks have stressed the importance of taking even minute safety risks seriously, not only to minimise adverse reactions but, more importantly, to prevent a broader undermining of public trust in vaccinations.

“Serious risks from vaccines, no matter how rare, are less tolerated than those caused by infection,” said Julie Leask, a vaccination specialist at the University of Sydney’s school of nursing. “Vaccination is taking an action that brings risk.” 

Leask said that while it was “extremely challenging” to get the messaging right, Australia’s advice on the AstraZeneca vaccine was an example of good risk communication.

The advisory, which recommended the Pfizer jab as the “preferred” vaccine for those under 50, included “detailed considerations” and “clear language”, while acknowledging trade-offs, Leask said.

“There is a science to good risk communication, such as how you best help people weigh up probabilities,” she said. “We should be using that.”

VACCINE HESITANCY

Still, there are signs of declining public trust in the vaccines, although it is impossible to say whether the slide has been driven more by the reports of side effects or the response of authorities to those reports.

The proportion of Americans who view the J&J vaccine as safe dropped 15 percentage points to 37 per cent following the pause by regulators, according to a survey carried out this month by YouGov America. The findings follow YouGov polling last month that showed major declines in trust in the AstraZeneca vaccine in Europe following the suspension of the jab, with more people in Germany, Spain and Italy now seeing it as unsafe than safe.

Schaefer, the Yong Loo Lin School of Medicine professor, cautioned against drawing conclusions based on a limited number of polls.

“Ultimately, trying to align public health policy with snap opinion polls is a fool’s errand,” he said. “We should aim for trustworthiness, not mere trust.”

But Iida Ruishalme, a biologist and science writer based in Finland, questioned whether authorities had fallen into the trap of being more averse to “man-made, unfamiliar risks” than “natural” risks such as disease.

“It seems to me that a focus on reducing overall risk, while being proactive about surveillance of the possible side-effects of vaccinations, would clearly be the best scenario here,” said Ruishalme, author of the Thoughtscapism science blog.

“Pausing vaccinations is a strong negative message against our best solutions, and should not be done lightly.”

Coronavirus: what if vaccines aren’t enough for herd immunity?

Suspending the vaccine “gives us a definite feeling of unease which is very difficult to repair by following messages trying to convince us otherwise”, Ruishalme said.

Jha, the Brown University School of Public Health dean, was concerned that authorities might be inadvertently fuelling anti-vaccine sentiment by overreacting to “what are ultimately extraordinarily rare events that happen all the time with therapies and vaccines and other things”.

He pointed to Britain, where authorities are offering people under 30 an alternative to the AstraZeneca shot, as an example of a country that had struck a sensible balance, and described Hong Kong’s cancellation of the jab as a response that “doesn’t make sense”.

According to YouGov polling released this month, 75 per cent of the British public considers the AstraZeneca jab to be very or somewhat safe, in stark contrast to widespread hesitancy in continental Europe.

Jha said that focusing so much on problems with the vaccines was the “wrong framework” during a once-in-a-century pandemic that has officially killed more than 3 million people worldwide.

“Given that so much of the world doesn’t even have any kind of vaccines at all, to look down on these incredible vaccines and keep them in the freezer as opposed to getting them into people’s arms, I find very, very unfortunate,” he said.