The Internet as anti-vaccine tool

It’s official now. The U.S. is on track to accumulate more cases of measles than it has seen in a decade:

The United States seems to be on track to have more measles cases than any year in more than a decade, with virtually all cases linked to other countries, including Europe where there’s a big outbreak.

Already there have been 89 cases reported so far. The U.S. normally sees only about 50 cases of measles in a year thanks to vaccinations.

Health officials are reluctant to make predictions, but acknowledge the pace of reports is unusually hot.

“It’s hard to say, but we’re certainly getting a lot,” said Dr. Greg Wallace, who leads the measles, mumps, rubella and polio team at the U.S. Centers for Disease Control and Prevention.

Europe, especially France, has been hit hard by measles, with more than 6,500 cases reported in 33 nations. International health officials are blaming it on the failure to vaccinate all children.

Just about all U.S. outbreaks were sparked by people bringing it here from other countries. This week, international health officials posted an alert urging travelers everywhere to get the recommended two doses of vaccine before flying overseas.


For the most part, U.S. measles vaccination rates remain reassuringly high. However, even though overall vaccination rates remain high, there appear to be increasing numbers of pockets of vaccine resistance where the percentage of vaccine uptake has fallen below that necessary for herd immunity, particularly in affluent coastal cities. When that happens, if measles finds its way into a community with low vaccine uptake rates, the chance of an outbreak, even a major outbreak, rises. Given that international travel is common and relatively easy, this means that low vaccine uptake rates overseas can represent a hazard to us here in the U.S., as travelers can bring the virus into populations whose herd immunity might not be adequate to prevent its spread. It also has to be remembered that the MMR vaccine, while very effective, is not 100% effective. As the article cited above notes, it’s quite possible to be fully vaccinated and become ill; the difference is that the odds of contracting measles are much lower if you’re vaccinated. That’s why the common anti-vaccine refrain that says that you shouldn’t worry about unvaccinated children being a threat to your children if you’ve vaccinated them is nonsense. True, they’re not as big a threat, but they’re still a threat.

The anti-vaccine movement, at least the Wakefieldian wing that says that the MMR vaccine causes autism, is definitely stronger in the U.K. than it is here and arguably also stronger in Europe than it it is here. It is therefore not surprising that we are seeing cases of measles in the U.S. as a result of European travelers bringing it here, although that is by no means the only source; travelers from Third World countries, where vaccine uptake rates can be quite low, are another major source. If we are not careful, MMR uptake rates could fall here as well, perhaps making American travelers vectors of infection delivering measles virus to other countries. Given how incredibly infectious and easily transmissible the measles virus is, it doesn’t take a lot. Be that as it may, it was interesting to me that less than a day before seeing the report above, I had run into this analysis on Eurosurveillance of the role of health information on the Internet in influencing decisions to vaccinate or not to vaccinate. After providing background about how vaccines have become a victim of their own success, such that people now focus far more on their potential side effects than the dangers of the diseases prevented by them, how distrust of vaccines fueled by the anti-vaccine movement has led to decreases in vaccine uptake rates, particularly in the U.K., and how the WHO failed to reach its goal of eradicating measles by 2010 and had to push that target back to 2015, the report sets the stage:

This paper takes a first step in exploring the role of the Internet in influencing anti-vaccination decisions from a psychological perspective and examines how vaccination risk perception and decision process are affected by information on the Internet. The main points were also presented at the 2010 Eurovaccine conference [6]. From a psychological point of view it is assumed that during the pre-decisional phase of the decision process, the problem at hand (to vaccinate or not) is identified and the person making the decision acquires the necessary information, e.g. via an Internet search (see Figure 1) [7]. In the selectional phase, potential outcomes of the alternatives are evaluated (appraisal, e.g. the risk of suffering from side effects after vaccination). Finally the decision is made. In the post-decisional phase the decision needs to be implemented and the person making the decision receives feedback (e.g. about the actual occurrence of side effects). All information is stored in the memory and will influence future decision processes. This paper focuses mainly on information search, its influence on risk perceptions, vaccination intention and finally behaviour.

So this study is looking solely at the pre-decision phase of vaccination; i.e., the information-gathering phase. As part of that analysis, the author first summarized data regarding the Internet as a source of health information in general and anti-vaccine information in particular, with some disturbing observations, making a rather disturbing observation. As a test case, a search was made for “hand cleaning” during the H1N1 pandemic of 2009-1010, which lead to WHO recommendations about handwashing and other infection prevention recommendations 75-80% of the time. In other words, for this term, the chance of someone searching about information on hand washing finding reliable health information was quite high, although I must admit that I was surprised that the percentage was only 80% at best. In contrast, searching for terms related to vaccines tend to have a higher chance of pulling up anti-vaccine websites, with the further observation that, the more general the term used, the more likely that anti-vaccine websites will appear higher on Google search results. This is relevant because of recent work cited that suggests that the parents’ knowledge about vaccination influence the complexity of the search terms they use. Parents who are better-informed will use more specific and complex search terms and be less likely to find anti-vaccine websites. In contrast, less knowledgeable parents are more likely to conduct searches and use less complex terms in doing so, leading to more anti-vaccine websites, which they are less able to evaluate critically because of their lack of knowledge. It’s a vicious circle.

The bottom line is that, as much as we make fun of them (and rightfully so, at least from a scientific perspective), anti-vaccine websites are effective through recycling several common arguments:

In terms of page content, all eight vaccine-critical Internet sites analysed by [3] were concerned with vaccine safety and claim a causal relationship between vaccinations and illnesses of unknown origin, e.g. multiple sclerosis, autism, asthma and sudden infant death syndrome. Arguments are continually repeated, for example: vaccines erode immunity (seven of eight), create only temporary or ineffective immunity (seven of eight), contain many ingredients and preservatives that will make you sick (eight of eight), overwhelm children’s immune systems, especially when administered in combination (three of eight). At the same time, treatments superior to vaccination are promoted, e.g. homeopathy (seven of eight). In addition, anti-vaccination websites are very well connected, as they all provide links to similar sites [3].

It’s true, too. One of the reasons anti-vaccine websites tend to percolate up so high on Google search results is because they are so highly inter-linked. They often have savvy web designers who know how to optimize their pages and blogs to appear as high as possible on Google search results for vaccine-related terms. In contrast, we who defend science-based medicine against the pseudoscience of the anti-vaccine movement are often far behind the curve.

But why are anti-vaccine websites so effective? The Eurosurveillance analysis confirms something I’ve been writing about from the very beginning of this blog, namely the power of testimonials. Testimonials aren’t just for cancer; they work for lots of anti-science and quackery, and their power is widely harnessed to serve the anti-vaccine movement by appealing to the emotions of parents, which when it comes to their children are particularly powerful:

A key feature on seven of the eight examined websites was the inclusion of emotive appeals, such as pictures and stories of children who were supposedly harmed by vaccinations. An example for such descriptions of personal experiences, posted on a German website, reads as follows: ‘My four year-old daughter received the five-in-one combination vaccine at nine months, she then had a fever for two weeks, was apathetic and had screaming fits, since then she has suffered from atopic dermatitis and many allergies. My son is now four months old and I don’t know if I should get him vaccinated or not (…)’. Parents appear to have a preference for personal information when searching on health related topics, i.e. information from parent to parent: even parents-to-be already search for such information, mainly through internet forums (bulletin boards) where they can post questions that are then answered by other parents [15].

The author summarizes that approximately 1 in 5 hits in Google searches on vaccines will lead to anti-vaccine websites and blogs (which, quite frankly, strikes me as a bit low, but the study was done before the rise of Twitter and Facebook), the vast majority of which prefer frightening testimonials of “vaccine injury” over scientific evidence. Indeed, one of my favorite examples of this the NVIC International Memorial for Vaccine Victims, which is nothing more than a bunch of unsubstantiated testimonials in which the adverse reaction reported may or may not be related to vaccines. Jenny McCarthy’s anti-vaccine group Generation Rescue takes it one step further, with a webpage featuring “vaccine-injured” children who were “recovered” using biomedical quackery. Because, as I’ve discussed many times before, correlation does not necessarily equal causation and autism is a condition of developmental delay with waxing and waning symptoms, these stories seem very compelling on the surface. These testimonials can be highly effective in producing an exaggerated perception of risk due to vaccines and an incorrectly low estimate of vaccine effectiveness in preventing disease. It is, as I have at times characterized it, misinformed consent, because the parent is refusing vaccination based on misinformation.

The effectiveness of misinformed consent is illustrated in this graph from the report:

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As you can see, anti-vaccine websites increase parents’ estimation of the risk of vaccinated and decrease their estimation of the risk of not vaccinating, the latter of which is frequently downplayed heavily in anti-vaccine websites.

So how to combat this emotive misinformation? Based on this report, it’s hard to say. The author discusses the use of emotive pro-vaccine appeals that play on the fear of disease, for instance by showing pictures of children who suffered encephalopathy after measles? However, most scientists are very uncomfortable about this approach, and the author correctly asks, “Should fear be fought with fear?” She also cites a study finding that stronger statements of risk negation can paradoxically lead to a higher perception of risk than weaker statements of risk negation, as well indicating that the source matters a lot. Indeed, strong statements of risk negation by a source parents find untrustworthy actually appear to increase the perception of risk. Of course, different parents will find different sources more or less trustworthy. For instance, anti-vaccine parents do not trust Paul Offit; his pronouncements are actually probably more likely to harden their positions. However, parents who are on the fence probably do not view him as negatively and might even view him positively, making him more effective with this population.

The resurgence of measles stresses the particular urgency to answering the question of how to communicate science and relative risk accurately to the public in a way they can understand. Failure could well result in the return of, if not the bad old days before vaccines could prevent so many deadly diseases, days that are quite bad enough.