A new study assesses the influence of anti-vaccination tweets on residents of the United States counties where they were sent.

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Online misinformation about vaccines may have a negative influence on people’s attitudes and behavior.

Health professionals consider vaccines to be one of the great achievements of modern medicine. Even so, skepticism over their value and safety has always existed, dating back to the smallpox vaccines of the 1800s.

Today, many people still oppose vaccines, while anti-vaccine misinformation proliferates online.

However, a new study finds the effect of online anti-vaccine misinformation minimizes in people who talk about vaccines with friends and family.

The study looks at anti-vaccination sentiment during the 2018–2019 flu season. It explores the impact of online misinformation about vaccines and the flu, and its lasting effects.

The research, which appears in the journal Vaccine, combines an analysis of tweets with surveys of U.S. adults. The study authors are Man-pui Sally Chan and Dolores Albarracín of the University of Illinois at Urbana-Champaign, and Kathleen Hall Jamieson of The Annenberg Public Policy Center of the University of Pennsylvania in Philadelphia.

“What we find,” says Albarracín, “is that some online discussions appear to have a negative influence on people’s attitudes and vaccine behavior — which makes the people exposed to them less likely to get a flu shot.”

This is particularly concerning due to the potential arrival of a COVID-19 vaccine. As Albarracín says, “What’s going to happen when we have a COVID-19 vaccine? If public health officials don’t offer clear, consistent messaging on vaccination, whatever circulates on Twitter — however crazy it is — may have an impact. We cannot trivialize it.”

Fortunately, the study finds conversation can reverse the damage done by misinformation. It is a problem, Albarracín says, if people “do not have real-world discussions about vaccination with family and friends. But if they discuss it with others, that effect goes away.”

Because “[t]weets, including retweets, are informative about popular topics and conversations within a community,” as the study asserts, the researchers used unsupervised machine learning to analyze 115,330 tweets relating to vaccine and flu-related messages.

Tweets were geolocated, since understanding where they came from has proven valuable in the past. The authors explain:

“Prior studies have shown that county-level tweets can provide signals for predicting HIV/STI infections, and are associated with attitudes, knowledge, and behaviors of infectious diseases, such as Zika across U.S. counties.”

The researchers examined the tweets alongside survey data collected in five waves, with each wave including up to 3,005 participants. They questioned each individual about their opinion of vaccines, their history of receiving them, and whether they discussed vaccination with anyone else.

Ten topics were identified from the tweet analysis, with two strongly associated with local anti-vaccine attitudes and behaviors among survey respondents who had not discussed vaccines with others.

The study authors named the tweet topics “Vaccine Fraud and Children” and “Vaccine Science Matters.”

  • “Vaccine Fraud and Children” tweets included the words “child,” “kid,” and “worldwide.” These tweets repeated discredited anti-vaccine claims from 2014 and included comments regarding kidney pathology.
  • “Vaccine Science Matters” consisted of tweets with the words “vaxwithme,” “ivcx,” and “cancer.” Tweets posted in November to February were positively linked to local vaccination attitudes in February and March.

A third topic, “Big Pharma,” was also associated with negative vaccine attitudes and behaviors.

The researchers caution that although they found “strong to very strong associations” between tweets and attitudes and behaviors relating to vaccines, associations do not prove causality, and further experiments are needed.

Despite this, the research suggests a simple but effective way to resist online misinformation about vaccines.

Lead author Chan adds, “Combating the current ‘infodemic’ online is critical, but so is getting communities to talk about vaccines in daily life.”

“We should be inviting families and communities to have open discussions on these issues,” says Albarracín. “You don’t necessarily have to tell people what to do, but that at least puts the issue on the table.”