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Misinformation about COVID-19 vaccines can appear almost anywhere: From an uncle's social media post to a well-trusted news commentator. But where does it come from and why do some myths spread further than others?

With the help of the internet research firm Graphika, NPR analyzed the rise of one persistent set of lies about COVID-19 vaccines: That they can affect female

Despite a mountain of scientific evidence showing the vaccines are safe and effective, the false information persists. 

To spread fear about COVID vaccines

Just 12 people are behind most vaccine hoaxes on social media

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Graphika's data analysis tools allow them to track key points at which a piece of information is shared or amplified. It can illustrate how many of these kinds of lies often go viral. 

The events outlined here represent a major amplification event for this false information, but they're by no means the only source of lies about female fertility and the vaccine. Claims about fertility and the coronavirus vaccines go back to at least December, and fertility claims about other vaccines date back even further, in some cases decades.

But the events of earlier this year illustrate how misinformation can spread in a nonlinear manner, with many different players adding threads to a web of false content. 

After receiving the COVID-19 vaccine this spring, "a lot of women noted heavy menstrual periods," says Alice Lu-Culligan, an MD-PhD candidate at Yale University who studies the immune system and reproductive health. 

Lu-Culligan says that immune cells play an important role in menstruation, and so it is in fact possible that the vaccine could temporarily alter that process. "It's very plausible that you could have abnormalities to the typical menstrual cycle," she says.

Researchers are starting to study the issue

Other scientists agree its possible. One team of medical anthropologists is conducting 

 of women's experiences with the vaccines, which has had over 120,000 response so far, according to 

, a researcher at University of Illinois Urbana-Champaign. They learned many thousands of women have unusually heavy flows after vaccination, and some older people also experienced breakthrough bleeding. 

Unfortunately, definitively establishing a link has proved difficult, in large part because trials for the new vaccines never asked women about their periods. Because there is so much natural variation in women's periods month to month, a controlled clinical trial would be needed to try and establish whether it was happening. "When you don't collect these data during the clinical trial, you really lose an opportunity to study it in a controlled fashion," Lu-Culligan says.

The lost opportunity for scientists became an opening for anti-vaccine activists, says Melanie Smith, former director of analysis for Graphika. "In the more successful misinformation cases that we see, there is always that gap of knowledge," she says.

Step 2: Find an influencer to spread doubts and questions 

With no firm data, stories about the disruption to menstrual cycles began popping up in forums and groups. Many were just wondering if it had happened to others, and whether they should be worried. But there was one Facebook group in particular that turned out to be important. 

"It's called, literally 'COVID-19 Vaccine Side Effects,' " Smith says. There were a lot of posts by ordinary people there, looking for answers, but anti-vaccine activists were also part of the group.

One of the people reading this page was an anti-vaccine campaigner named Naomi Wolf. Formerly best-known for her writing about feminism, Wolf has, over the years, drifted into anti-vaccine advocacy. "She is a very highly followed influencer in what we call the pseudo-medical community," Smith says.

Wolf is not a medical doctor, and yet on April 19, she tweeted out a link to the Facebook group along with this message: "Hundreds of women on this page say that they are having bleeding/clotting after vaccination, or that they bleed oddly AROUND vaccinated women. Unconfirmed, needs more investigation, but lots of reports."

Smith points out that Wolf is using an old trick: by saying something "needs more investigation," she's raising doubts, without presenting facts that can be refuted. 

Wolf's tweet also seamlessly inserted a myth: that somehow vaccinated women could pass side effects on to the unvaccinated. 

Lu-Culligan says that's absolutely not the case. She adds that this myth seems to echo another popular falsehood: that somehow women who live together can influence each other's cycles. 

Wolf kept tweeting, and piling on more misinformation in question form: Can vaccines cause infertility? Miscarriages? 

This slam went well beyond disruption to menstrual cycles, raising the stakes dramatically.

Lu-Culligan says that the evidence overwhelmingly shows that the vaccines do not cause these problems. "At this point there have been many many millions of women who have gotten the vaccine and there have been no scientific reports of any infertility," she says. 

The Centers for Disease Control and Prevention also says that the available data shows 

that vaccines are safe for those who are pregnant or nursing

Days after Wolf started tweeting about vaccines and fertility, other influencers began picking it up, and a few clickbait websites wrote fake news stories.

But it was the real news that gave the lies their biggest boost. About a week after the initial tweets, a Miami private school, the Centner Academy, announced it would no longer allow vaccinated teachers into the classroom. It said there were too many questions about whether the vaccine could spread to unvaccinated mothers and children. 

The school's CEO, Leila Centner, is an established anti-vaccine advocate, so her decision wasn't surprising. But the ban made national news anyway.

"To some people it's crazy and to others they question it because they want to know more, so for everyone there's a reason why you click on it," says 

 is a senior scholar at the Johns Hopkins Center for Health Security. She says this perfectly illustrates how a lie that's grown big enough can use the mainstream media to get a further boost. 

"By covering it, which is important for people to know what kind of stuff is going on out there, the other side of that is that the lie spreads faster and more people see it and more people pick up on it," Sell says.

And that's what happened.  The Miami school story led to global coverage. "This is the point at which we start to see Spanish and Portuguese content, specifically," says Graphika's Smith.

The lies piggybacked along with news of the school. Outlets in other languages began reporting that the vaccine can spread person to person, or cause fertility problems.

Finally, because misinformation about vaccines is not grounded in data, it can mutate to fit any political message or worldview. 

Vaccine myths about fertility and reproduction are particularly potent because they affect a large swath of the population, particularly when they incorporate myths about vaccinated

women spreading the side effects. "It's kind of a one-size-fits-all theory in some ways, and the potential impact is everyone, rather than one specific community," Smith says.

In the weeks following the initial wave of coverage, others were using these ideas to grab audiences. Conservative commentator Candace Owens brought the link between vaccines and menstruation up on Instagram. In a six-minute video questioning vaccine safety, Owens never directly repeated the lies about fertility, but didn't refute them either. 

Far-right commentator Alex Jones folded the vaccine lies into his conspiracy theories about Google and Facebook, which he claims are trying to depopulate the earth. "It's not just that you're going to be sterile, you're not going to be able to have children," Jones said during a recent broadcast. "You're not going to be able to eat beef anymore."

By late June, the lies about fertility had spread everywhere from France to Brazil. But then, researcher Melanie Smith says, they started fading away.

"It seems to have kind of fallen by the wayside in terms of the COVID-19 news cycle that happens in these spaces on the internet," she says.

And that's the last lesson about the lies: They don't stick around. They grab the attention, raise questions and doubt, but there's no substance there. So once they've shocked those they're meant to engage, they disappear. 

Or more properly, they're replaced by a new, incredible story. 

Can You Believe It?

Health

COVID-19

Geoff Brumfiel

Author

Where do myths about coronavirus vaccines come from and why do they spread? NPR takes a look at how rumors about vaccines and fertility reached the public earlier this year.

The life cycle of a COVID-19 vaccine lie

Go Deeper.

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