By Greg Ip 

On Tuesday, regulators recommended pausing the rollout of Johnson & Johnson's Covid-19 vaccine out of "an abundance of caution" after six out of nearly 7 million recipients developed dangerous blood clots.

For one of the regulators, the U.S. Food and Drug Administration, the decision was entirely in character: it has always put a premium on safety. That doesn't necessarily make it the safe choice. Covid-19 infects more than 60,000 Americans and kills more than 900 every day. A pause of even a few days could add to that toll.

"It's very clear that the dangers of Covid are much larger than the dangers of the J&J vaccine or the AstraZeneca vaccine for that matter," said Alex Tabarrok, an economist at George Mason University who has advocated for bolder approval and distribution of vaccines. "I worry that the public will confuse a pause to mean that the FDA thinks people shouldn't take the J&J vaccine."

It's too soon to know the ultimate net effect of the pause on health. Still, Britain kept administering AstraZeneca's vaccine when similar blood clotting was reported and the evidence so far seems to back it up.

The Winton Centre for Risk and Evidence Communication, based at the University of Cambridge, estimates the virus is a much bigger risk than blood clots to recipients of almost all ages and exposures. In every 100,000 people in their 40s with low exposure to the virus, the vaccine will cause blood clots in 0.5 while preventing Covid-19 serious enough to require intensive care in six others, it says. Among people in their 60s with high exposure, the vaccine would cause blood clots for 0.2 while preventing an ICU visit for 128. Only for people in their 20s with low exposure did it find risks are roughly equal. British regulators have advised that people under 30 be offered a different vaccine.

This doesn't necessarily mean the FDA is wrong. It may simply use the pause to develop more detailed guidance for at-risk recipients, and meanwhile vaccines by Pfizer Inc. and Moderna Inc. are readily available.

Still, it's the latest example of how Americans have struggled to be rational about risk throughout the pandemic. The unknowns about the virus were bound to make decisions error-prone. Emotion, misinformation and polarized politics make rational cost-benefit analysis even harder.

For example, ample evidence shows masks significantly reduce transmission at little economic cost, yet some Republican governors have refused to enact or maintain mask mandates. Evidence similarly shows schools with mitigation measures don't worsen the spread of the virus and remote learning is hugely costly to children and families. Yet until recently many predominantly Democratic leaders have kept children out of class.

The FDA and the U.S. Centers for Disease Control and Prevention, though generally more faithful to science and statistics than politicians, often default to the "precautionary principle" -- erring on the side of safety when science is at all uncertain. This is sometimes traced to the 1960s, when the FDA was praised for not approving thalidomide, a drug for morning sickness that turned out to cause birth defects.

That has resulted in what Mr. Tabarrok calls an "overabundance of caution." In the past, people died from preventable diseases because the FDA was slow to approve treatments, he said. "Throughout this crisis, we have acted too slowly and been too cautious."

Mr. Tabarrok, like many experts, has urged the U.S. to postpone the second of the Moderna and Pfizer vaccines' two shots so that more people get at least one. They argue that while each individual would have slightly less protection, the country as a whole would reach "herd immunity" faster, saving countless lives. But U.S. regulators have stuck with the two-shot regimen, because approval was based on the durable immunity the two-dose regimen demonstrated in trials.

Britain decided in December to delay the second of its vaccines' recommended two shots. As a result it has vaccinated more of its population than any major country except Israel, and its infection rate has gone from among the highest in the developed world to among the lowest (a lockdown helped).

Since early in the pandemic, some epidemiologists have pushed for rapid, cheap Covid-19 antigen tests that, while less accurate than better-known PCR tests, could be administered at home en masse, catching enough infections to halt transmission and allow schools and businesses to reopen. But the FDA has been slow to approve them, undermining their potential. The FDA has also yet to approve AstraZeneca's vaccine despite approval in many other countries. This month, the CDC declared it was safe for vaccinated people to travel, while advising them against doing so. Critics say such guidance diminishes the incentive to get vaccinated.

Yet set against its history, the FDA actually has moved relatively quickly. Robert Wachter, chair of the department of medicine at the University of California, San Francisco, notes it granted all three Covid-19 vaccines "emergency use authorization," which it seldom did for vaccines in the past.

He said the authorization ensured millions of people could receive the J&J vaccine a year or two sooner, while monitoring continued for side effects that are too rare to show up in trials -- such as the blood clots. "We are seeing...the system working magnificently well."

Alexandra Freeman, executive director of the Winton Center, said willingness to get vaccinated depends less on numbers than on trust: "You can't personally see the benefits, so you have to trust somebody else. Imagine you were offered the Chinese, or North Korean or Russian vaccine: would you put your arm out and say yes? You might think twice." Blood clot reports don't appear to have reduced Britons' vaccine take-up, possibly because they trust the regulators, she said.

Trust may thus justify the pause in J&J's vaccine rollout, even if raw cost-benefit calculus does not. By showing they would act on any evidence a vaccine is unsafe, regulators hope the public will believe them when they say a vaccine is safe.

Write to Greg Ip at


(END) Dow Jones Newswires

April 14, 2021 11:09 ET (15:09 GMT)

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