The J&J vaccine is back. Next comes trust.

Last week US regulators recommended resuming use of the Johnson & Johnson vaccine, after deciding that a side effect involving blood clots was too rare to justify continuing the brief suspension they had imposed: there were just 15 reported instances out of 8 million doses. But even though the pause lasted just 11 days, it raised new concerns about whether Americans will trust vaccinations. Recent polling shows that confidence in the Johnson & Johnson shot in particular is very low, with 73% of unvaccinated people saying they wouldn't accept a dose if offered.

That could pose new challenges for health-care providers, public health departments, and other government officials working to get everyone vaccinated.

Ben Weston, director of medical services at the Milwaukee County Office of Emergency Management in Wisconsin, says that some confidence has been lost, and restoring it is going to take time and effort.

We're all still trying to figure out the best way to message that it actually is a very safe vaccine," Weston says. Nationally-and internationally, for that matter-we have a lot of work to do to continue to instill confidence in all the vaccines."

However, not everyone thinks the hiatus necessarily set those efforts back. Holly Fernandez Lynch, an assistant professor of medical ethics at the University of Pennsylvania, says that pausing the vaccine even for such a rare side effect could actually leave people feeling more secure-if government officials can communicate the message effectively.

The regulators exist to keep you safe. They paused when they saw a safety concern. You can trust when they allow things to resume," says Fernandez Lynch, who studies the Food and Drug Administration and its policies. The regulatory system is working exactly as it's intended."

Seema Shah, a bioethicist at Lurie Children's Hospital in Chicago, says that though the pause wasn't ideal, forging ahead on distributing the Johnson & Johnson shot without stopping to investigate the clots would have been worse.

I keep thinking about the counterfactual," says. If the FDA hadn't paused, what kind of signal would that have sent?"

Having options can increase trust

Many health-care providers and government officials have seen the Johnson & Johnson vaccine, which uses conventional virus-based technology to deliver the needed genetic instructions, as a useful alternative to the mRNA vaccines from Pfizer and Moderna. Because it requires just one dose, it is well suited for people who may not stay in one place long enough to schedule a second dose, such as college students and people experiencing homelessness.

Many other people simply prefer the one-shot option-whether for convenience or because they don't like needles to begin with. Gig and shift workers may have narrow windows in which they can get to a vaccine appointment, making Johnson & Johnson a better option.

The Johnson & Johnson vaccine is also easier to distribute and administer because it doesn't need the especially cold storage temperatures that mRNA vaccines require. That makes it convenient for vaccinating homebound patients, people in rural communities, and patients at pop-up clinics that may not have special freezers.

If the FDA hadn't paused, what kind of signal would that have sent?"

Seema Shah, bioethicist at Lurie Children's Hospital in Chicago

But despite these benefits, the vaccine engendered mistrust after manufacturing issues and studies that showed it was less effective at preventing infection: while the Pfizer and Moderna vaccines were 95% and 94% effective against symptomatic infections, the Johnson & Johnson shot was 72% effective against moderate to severe cases. Though the comparison isn't perfect, seeing headlines about inferiority can add up, and those who are working to build trust need to take them into account.

It's going to require some important messaging to help people understand we're not foisting the bad vaccine on you-there isn't a bad vaccine that we would allow to stay in use," Fernandez Lynch says. She also notes that doctors will now need to communicate with patients to win their confidence. They're the ones who can explain the relatively low risk of side effects, or offer alternatives for those who are concerned.

Building that trust is a long game, she says: It's not just about today; it's not just about the J&J vaccine; it's not just about covid vaccines. It's about trust in science, the government, and public health."

This story is part of the Pandemic Technology Project, supported by the Rockefeller Foundation.