COVID-19 is the first major pandemic in the social media era — offering experts a rare opening to study the relationship between online misinformation and human behavior on a large scale.

Why it matters: As misinformation about COVID-19 vaccines runs rampant, researchers are trying to measure how much memes and messages with false information can alter someone's decision to get vaccinated.

What's happening: Daily COVID-19 vaccinations in the U.S. have slowed over the past month, and those Americans remaining are less enthusiastic about being vaccinated, suggesting the country is hitting a vaccine wall.

• "There is mounting evidence that exposure to certain types of media is associated with hesitancy," says Kayla de la Haye, who studies social networks and their impact on health and disease prevention at the University of Southern California.
• Tech platforms are scrambling to deal with vaccine disinformation, but experts argue they may be too late and misinformation is persisting. Earlier this year, Facebook said it would remove groups and pages that may discourage people from getting vaccines, after initially saying it wouldn't treat vaccine misinformation with as much rigor as regular COVID-19 misinformation.

Details: In a recent Axios-Ipsos poll, "people who either believed misinformation or were unsure whether it was true or false were less likely to get the vaccine than those who knew that it was false," Axios' David Nather reported.

• Researchers at Indiana University's Observatory on Social Media found states where a higher percentage of discussions on Twitter included low-credibility sources also tended to have a higher percentage of people who are hesitant to take a vaccine.
• In another study, published earlier this year, knowledge and misinformation emerged as key predictors of whether someone intended to get vaccinated.
• Exposure to vaccine misinformation "induced a decline in intent" to get vaccinated among people in the U.S. and U.K., according to a study published in February.

Yes, but: It's really hard to connect exposure to misinformation to behaviors, says de la Haye. That's because of "the difficulty of monitoring what an individual gets exposed to online and what they subsequently go and do."

• "There's a recognition this is a big problem, but it's a problem that's part of a complicated set of factors that influence whether someone gets vaccinated," she says.
• A person's political affiliation, assessment of their own risk of disease, access to vaccines, technology and transportation, and socioeconomic status are also factors, many of which are interconnected.
• Matthew DeVerna, a graduate student and collaborator on the CoVaxxy project at Indiana University, says the team is working to tease misinformation out from other factors that may influence vaccination behavior, including poverty, age, the number of COVID-19 deaths in an area and more.

The big picture: One word dominates the reasons people give for being hesitant or resistant to getting a COVID-19 vaccine: trust, says David Lazer, a professor of political science and computer and information science at Northeastern University who, with his collaborators, has conducted dozens of surveys over the past year to study people's attitudes and behaviors during the pandemic.

• A lack of trust in government, companies or institutions may be why some people accept misinformation and even actively seek it, and why they are skeptical of getting vaccinated, he says.

What to watch ... the roughly 30 million Americans who aren't saying they won't get a vaccine or are waiting but say they'll do it when they can.

• Some people who refuse the COVID-19 vaccines are heavily entrenched in a well-funded, well-organized anti-vaccine movement, but others who are considered hesitant are trying to make an informed decision while encountering a wave of disinformation, says Samuel Scarpino, a business professor of network science at Northeastern University College of Science.
• "I’m skeptical that reaching them is by convincing Facebook to remove misinformation and more about taking vaccines out to people and reducing the friction of 'I can’t be bothered,'" Scarpino says, pointing to efforts to vaccinate people on the New York City subway, at baseball games and in churches.

The bottom line: "Even if there isn’t a whole lot we can do about fighting misinformation or backing out its individual contribution to hesitancy, it doesn’t mean there isn’t a whole lot else we can do," Scarpino says.