Zika Vaccine Misconceptions: A Social Media Analysis

"...once people believe something, it is difficult to dissuade them. Public health officials must get out in front of the conspiracy theorists to educate and influence the population now."

This study analyses conversations about Zika vaccine conspiracy theories on social media in real-time in an attempt to provide a method that could help officials debunk claims quickly enough to limit the damage they cause to vaccination rates. As the Zika virus spread through South America, conspiracy theories spread through social media (and eventually made their way into mainstream media). Much uncertainty still surrounds the origin and effects of the Zika virus. This has resulted in doubts about whether microcephaly is truly caused by the virus and whether future vaccinations will be safe. These suspicions, bolstered by social media posts, can have a lasting effect on people's health-related decisions, the researchers said

The researchers identified 138,513 Twitter messages from January 1 to April 29 2016 that contained both vaccine keywords and a reference to Zika. Figure 1 in the paper (see also above) shows a rapid rise in the number of Zika vaccine tweets in those weeks, coinciding with increased media attention around the outbreak. They then identified which of these tweets mentioned pseudo-scientific claims; Figure 1 shows that a rapid rise in tweets associated with pseudo-scientific claims coincides with overall interest increases, which suggests that people quickly subscribe to these theories, many months to years before a vaccine is even ready.

As the researchers explain, the leading pseudo-scientific claims build on existing narratives, making them more persuasive because they appear to reinforce and confirm already-held beliefs. In one theory, it is not the Zika virus, but pyriproxyfen, a mosquito larvacide allegedly made by Monsanto (the "third most-hated company in America") that led to microcephaly among infants; this story was readily believable to people who already view Monsanto negatively. (Monsanto does not make the larvicide in question, nor has evidence linked larvicide to the microcephaly cases). In a second prominent theory, microcephaly is attributed to side effects of existing vaccines, such as meales, mumps, and rubella (MMR) or Tdap and the desire of pharmaceutical companies to profit from blaming the Zika virus. This theory conforms to existing narratives that claim vaccines have dangerous side effects and pharmaceutical companies use them to bolster profits. These pseudo-scientific claims are frequently being advanced by existing vaccine-skeptic communities.

The researchers observe that pseudoscience claims are most impactful when the most possible people are exposed to them in a vulnerable state. In the case of Zika conspiracy theories, the most vulnerable people were those who were concerned and looking online for information about Zika virus and microcephaly.

It is recommended that public health experts act to quickly address people's concerns and debunk unscientific claims to ensure that a future vaccine campaign is effective. One way to do this, the researchers hold, is to use their team's method of tracking conversations on social media. This tactic, they say, cuts the time it takes to discover what people are talking about and paves the way for a prompt public health response. Looking forward: "Research must assess subgroups of the population to determine their varying cognitive decision-making styles about vaccination, in order to appropriately target messages that will resonate with each group, rather than a one-size-fits-all approach."

Although this work did not directly explore the role of pseudoscientific claims on vaccine uptake (because there is no Zika vaccine at the time of this writing), the researchers suggest that future work focus on testing the effects of these claims on vaccination rates, as well as reportable psychometric measures such as intention to vaccinate, in controlled experimental settings as well as in quasi-experiments on social media.