The Johnson & Johnson vaccine pause dealt a blow to the U.S. vaccination effort, but given that the vaccine only made up 5 percent of the shots given domestically, experts think it will likely have a much greater impact abroad.

Here are five ways the pause could reverberate worldwide:

Jeopardize the global vaccine effort

Safety warnings about Johnson & Johnson's vaccine and a potential link to a rare but serious type of blood clot could hamper efforts to speed vaccinations in developing countries.

Combined with the vaccine manufactured by AstraZeneca, Johnson & Johnson's single-dose shot is meant to be a major part of the global supply of coronavirus vaccines.

The company is slated to provide up to a billion doses to countries around the world. It's easy to store, without any complicated deep-freeze requirements like the mRNA vaccines made by Pfizer and Moderna, and Johnson & Johnson has pledged to sell the shots at cost, without making a profit.

But so far it has manufactured only a fraction of that amount, and questions about safety are likely to linger amid the supply shortages.

It's also not just the U.S. that decided to pause using the vaccine. Johnson & Johnson said it was pausing its European rollout, and health authorities in South Africa also announced that they were putting it on hold. Australia said it was not going to purchase any doses from J&J even as the nation struggles with its vaccination.

Increase vaccine hesitancy

Most experts said the impact on global supply would be fairly limited if countries resume using the J&J vaccine in the next week or two.

The bigger concern is that a pause of any duration could deal a blow to vaccine confidence.

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"The challenge is that anytime there is news of adverse events, that may have an impact on willingness to vaccinate, whether it be specifically with that vaccine, or vaccinate against COVID, more broadly," said Elizabeth Shakhnovich, a consultant with Oliver Wyman's Health & Life Science Practice.

A particular concern is that the decision to pause the use of J&J's shot followed the pauses of another adenovirus-based vaccine, developed by AstraZeneca and Oxford University, in the European Union and many of its member states.

"We watched this story over the last couple of weeks with AstraZeneca," Shakhnovich said. "There was some level of hesitancy around vaccination in general in Europe, and then the stories of adverse side effects emerged," and vindicated the vaccine skeptics.

American officials have taken great pains to say the Johnson & Johnson vaccine is safe, and they recommended the pause only out of an abundance of caution. But reasoning and nuance doesn't always filter through. People's faith in the shot will be undercut, even though it works.

"It ends up being a game of telephone. Unfortunately, six out of seven and a half million patients affected by clotting ... you know, that number doesn't necessarily get passed along correctly," said Vikram Bakhru, chief operating officer at ConsejoSano, a company specializing in health equity. Read more at The Hill