Public Health

Debunking Zika virus pseudoscience: we need to respond fast, say researchers

Conspiracy theories are putting vulnerable people at risk, and the public health response has to be speedy

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The number of Zika vaccine tweets and tweets with pseudo-scientific claims coincides for 7 day periods for the first 49 days of 2016. (Source: Dredze, Mark et al, <em>Vaccine</em>)

In 2015, a worrying trend emerged in Brazil: babies were being born with abnormally small heads and brains. The condition, called microcephaly, became thousands of times more common than usual, causing widespread panic in the region.

What was causing the abnormalities? All the signs pointed to Zika virus – a virus that is spread by mosquitos in South America, Africa and Asia. Scientists were cautious with the facts – although the evidence revealed a link between Zika virus and microcephaly, they couldn’t yet prove that the virus was causing the condition. But while researchers worked tirelessly to uncover the truth, something else was happening on social media: conspiracy theorists were taking over the story.

By early 2016, several pseudoscientific claims had been made and people had started to doubt Zika virus as the cause of microcephaly and question the motives behind a Zika virus vaccine. Similar stories about other vaccines in the past have led to reductions in vaccination rates – take the MMR scandal for example. False information in a study that was subsequently retracted resulted in conspiracy theories and hundreds of unnecessary deaths from measles. So for a Zika virus vaccination effort to be effective, public health authorities would need to respond to the claims quickly.

A new study published in Vaccine analyzes conversations about Zika vaccine conspiracy theories on social media provides a method that could help officials debunk claims quickly enough to limit the damage they cause to vaccination rates.

Tracking dangerous claims

As the virus spread through South America, conspiracy theories spread through social media. One such story was that microcephaly is caused by the MMR and DTap vaccines and pharmaceutical companies are blaming Zika virus in order to profit from selling Zika vaccines. If people who are concerned and searching for information about Zika come across this story, they may be led to avoid vaccination and distrust health authorities.

Another story came from a group of Argentinian doctors who published a report claiming that a pesticide they said was produced by Monsanto was the cause of microcephaly in Brazil, and that there was no connection to Zika virus. They urged people not to worry about infection and even avoid vaccination, since they believed it was likely to be dangerous.

But factually, almost everything in the report was wrong. There is no link between the pesticide and microcephaly, the pesticide is not used in the area they were writing about, and it’s not manufactured by Monsanto. In fact, every piece of the story comes from previous conspiracy theories, pulled together to create one believable story.

David Broniatowski, PhD“It somehow explains what’s going on, but it just so happens that everything they say is wrong,” said Dr. David Broniatowski, Assistant Professor in the School of Engineering and Applied Science at The George Washington University and corresponding author of the study. “The doctors had perfect timing with their claims; they jumped on the bandwagon in a pretty sophisticated way and played into vulnerable people’s biases.”

To investigate the impact of the claims, the team monitored Twitter in real-time, which meant they could identify conversations as soon as they happened. The method gave them a fast insight into what people were talking about online. They identified close to 140,000 tweets between January 1 and April, 2016, that contained the keywords “vaccine” and “Zika.” They observed a number of conspiracy theories, or pseudoscientific claims, questioning why governments wanted a vaccine.

The pseudoscientific claims about Zika virus peaked just as interest in the virus and vaccination peaked. This means people have been exposed to the conspiracy theories for months – long before any vaccines have been developed. And to make matters worse, these are the very people who are most susceptible to the claims.

Targeting the vulnerable

Pseudoscience claims are most impactful when the most possible people are exposed to them in a vulnerable state. In the case of this Zika conspiracy theory, the most vulnerable people were those who were concerned and looking online for information about Zika virus and microcephaly. Faced with claims of a government cover-up to force vaccinations, they were being scared into believing the worst and avoiding vaccination.

The nature of the claims and the strength with which they are being made can make people question the facts, even if they’re familiar with the science, says Prof. Broniatowski:

It makes you question your own knowledge – “wait a minute, did we miss something?” I’m an engineer and my colleague Dr. Dredze is a computer scientist, we’re not microbiologists but when the science is clear it guides us. Even this can make you double-take and look for more information. And if the scientific community’s response is too slow, these stories can really gain purchase.

It’s not possible to test the effects of pseudoscience claims on vaccination rates, so the researchers can’t be sure what would have happened in their absence. But they can see that the stories were repeated – including in the mainstream media – and shared, and they did have an impact on public opinion that’s unlikely to be positive.

So where do these stories come from? The motivations of the people behind them remain unclear; the researchers say it’s possible they genuinely believe what they’re saying, in which case they could think they’re doing a public service. Dr. Mark Dredze, Assistant Professor in the Department of Computer Science of Johns Hopkins University, explained:

The information people are spreading is consistent with a narrative they already believe. If you hold negative beliefs about vaccines and you don’t trust drug companies, for example, when you read about a new disease and the development of a new vaccine, you’re immediately suspicious. That’s partly what makes these stories so dangerous – they play into things people already believe to be true.

Debunking pseudoscience

There’s no question, Zika virus and microcephaly are scary things. It’s natural to be scared and look for an explanation. But if we find one, we have to be aware that it might not be correct, particularly if it’s on social media. After the initial wave of media coverage, many newspapers and websites, such as the New York Times, have come out against the claims. But they had already gained traction on social media, where information is not vetted and people can jump to conclusions quickly.

Mark Dredze, PhDSpeed is of the essence, then, when it comes to debunking the claims. “It’s in the best interests of public health communicators to prepare a response in real-time so if someone has one of these stories, health officials aren’t stuck,” Prof. Broniatowski said.

The team’s broader research perspective is about trying to understand how to help the most vulnerable communities resist disease. Perception can vary dramatically – for example, give five people the same information about the science of vaccines and they’ll conclude different things, depending on their own background and biases and how they process information.

Working out how to communicate reliable information to the most at-risk people in a way that they can understand and engage with it is key to ensuring public health. And analyzing social media provides a fast track to this information, Prof. Dredze said:

We know people in these communities perceive things differently, and we can use social media to find out how their perceptions vary. This method is much faster than other research methods like questionnaires – that’s important because if it takes years, we’ll be too late to have an impact on disease spread.

We really do have the capacity to determine how people are reacting to these diseases, so we can tailor our communications to what people are saying, not what we’re concerned they might be saying. We know the standard approach – giving people the numbers and facts – doesn’t work. So what does work? We’re making progress towards answering that question.

Read the study

Elsevier has made this article freely available until August 23, 2016:

Dredze, Mark et al: “Zika vaccine misconceptions: A social media analysis,” Vaccine (May 2016)


The lead author

Dr. Mark Dredze is an Assistant Research Professor in Computer Science at Johns Hopkins University and a research scientist at the Human Language Technology Center of Excellence. He is also affiliated with the Center for Language and Speech Processing and the Center for Population Health Information Technology. He is an expert in natural language processing and machine learning, with a focus on social media analysis. Dr. Dredze has pioneered the emerging field of public health applications of social media. He uses a wide array of data, including Internet search queries, social media and web forums to derive insights into public health. Dr. Dredze's work in public health covers a wide array of applications, including disease surveillance, vaccines, illicit drug use, behavioral responses to illness, patient safety, tobacco use and mental health. He obtained his PhD from the University of Pennsylvania in 2009.

The corresponding author

Dr. David Broniatowski, Director of the Decision Making and Systems Architecture Laboratory at The George Washington University, conducts research in decision making under risk, group decision making, system architecture and behavioral epidemiology. This research program draws upon a wide range of techniques including formal mathematical modeling, experimental design, automated text analysis and natural language processing, social and technical network analysis and big data. Current projects include a text network analysis of transcripts from the US Food and Drug Administration’s Circulatory Systems Advisory Panel meetings, a mathematical formalization of Fuzzy Trace Theory – a leading theory of decision-making under risk, derivation of metrics for flexibility and controllability for complex engineered socio-technical systems, and using Twitter data to conduct surveillance of influenza infection and the resulting social response.


The journal

The official journal of The Edward Jenner Society and The Japanese Society for Vaccinology, Vaccine is the pre-eminent journal for those interested in vaccines and vaccination. The journal covers a wide range of vaccine-related topics, including human and veterinary vaccines for infectious and non-infectious diseases, production and manufacturing, and regulatory, societal and legislation aspects. This journal is published by Elsevier.


Elsevier Connect Contributor

Lucy Goodchild-van
  HiltenAfter a few accidents, Lucy Goodchild van Hilten discovered that she’s a much better writer than a scientist. Following an MSc in the History of Science, Medicine and Technology at Imperial College London, she became Assistant Editor of Microbiology Today. A stint in the press office at Imperial saw her stories on the front pages, and she moved to Amsterdam to work at Elsevier as Senior Marketing Communications Manager for Life Sciences. She’s now a freelance writer at Tell Lucy. Tweet her @LucyGoodchild.

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