As Vaccine Awareness Week draws to a close, I thought it might be instructive to step back and look at the tactics, impact, and successes of the anti-vaccine movement. Yesterday, Orac questioned the best approach to counter the anti-vaccine movement. With today’s post, I’ll summarize two pertinent papers on the effectiveness of their tactics, and suggest some possible approaches.

There’s overwhelming evidence that vaccines have provided us with tremendous health benefits. Smallpox has been eliminated (except, apparently, for homeopathic nosodes), polio is almost gone, and occurrences of diseases like measles or rubella are now rare. In use for over a century, they are a public health triumph: diseases that terrified us a generation ago are now never seen.  Epidemiologic evidence demonstrates that vaccines have a remarkable safety record, and are exceptionally cost-effective interventions. Yet in spite of this, concerns about vaccine safety seemingly continue to mount.  And as we see time and time again, when vaccination levels drop, diseases reappear. So what’s driving anti-vaccine sentiment, and why is it successful?

The H1N1 pandemic of 2009/10 is now about a year past its peak, and is instructive as a case study on communication on  vaccine safety and efficacy. Remember the H1N1 vaccine? Judging by the anti-vaccine rhetoric of just last year, by now we should all have been rounded up by the army, given forced injections, and if the vaccine didn’t kill us right away, or make us walk backwards, we’d be immunosupressed (from the aluminum adjuvant), or have Gulf War Syndrome (from the squalene). And not only did it not work, it doubled our odds of getting H1N1.  All we needed was vitamin D and a proprietary supplement formula to avoid the flu, they said.

There’s a new paper that attempted to evaluate population-level sentiment about the vaccine, as well as the key sources of antivaccination information that circulated at the time. Neil Seeman, Alton Ing, and Carlos Rizo recently published Assessing and Responding in Real Time to Online Anti-vaccine Sentiment during a Flu Pandemic in the journal Healthcare Quarterly. The authors had two objectives: evaluate Canadian attitudes about the safety of the H1N1 vaccine during the fall of 2009; and to aggregate and quantify the vaccine-related information that was being circulated online.

Percieved Safety of the H1N1 Vaccine

The authors wanted to understand how perceptions of safety were changing during the flu season by surveying Canadians on a daily basis. They used a commercial program that redirects visitors to nonsense URLs that would be reached by random accidents in entering web addresses. URL names used had no commercial or English name. This process is similar to random-digit dialing for internet users, as any user could conceivably enter an incorrect web address and land on a tracked site. There was no intent to track users seeking vaccine information – the process would simply identify a random sampling of internet users. Users that landed on a tracked site were asked “Is the H1N1 flu vaccine safe?” and answers were restricted to “yes”, “no”, “I don’t know”, or “skip”. Basic demographic information was also collected. Only Canadian IP addresses were exposed to the survey.

Over 27,000 respondents (1,141 visitors per day) completed the survey out of 175,000 that landed on a URL, a decent response rate of 15.6%.  Response was evenly distributed from across Canada, but was predominately female (61%) and, compared to known internet user demographics, skewed towards younger Canadians, with older adults significantly underrepresented.

Here’s how vaccine safety was perceived by the survey population over time:


There’s no statistical analysis conducted, but it seems reasonable to assume that concerns about the vaccine’s safety were substantial, and possibly even increased slightly over time. During the survey period, 23.4% of Canadians considered the vaccine safe, compared to 41.4% who indicated it was unsafe, and 35.2% who expressed no opinion.

What Drives Perceptions of Safety?

In the second part of the paper (unrelated to the survey) the authors describe their attempts to understand information being circulated online about H1N1 vaccine safety. They identified and tracked over 17,000 Google search results based on (English language) Google searches, and then ranked them based on how frequently the information was shared via social networks like Digg, Facebook, YouTube and Twitter. On a daily basis, trending articles were reported and ranked in real time in their Flu Chat Lab. The authors aggregated the most shared links overall in an appendix to the paper.

Here are the results. Round up the usual suspects:

  1. YouTube video: Convenience store clerk touting Vitamin C and fish oil
  2. YouTube video: “Girl gets ‘Flu’ shot & now can only walk backwards”
  3. Mercola article: “Critical Alert: The Swine Flu Pandemic – Fact or Ficton?”
  4. Atlantic article: “Does the Vaccine Matter?”
  5. Prison Planet article: “CDC warns neurologists to watch for nerve disease following swine flu shots”
  6. “Is the H1N1 swine flu vaccine safe? What if I’m pregnant?”
  7. Mercola article: “Swine Flu – One of the Most Massive Cover-ups in American History”
  8. article: Assistant Surgeon General Dr. Anne Schuchat dispels myths about the H1N1 flu virus on The Doctors
  9. Mercola article: “Warning: Swine Flu Shot Linked to Killer Nerve Disease”
  10. Mercola article: “Alert: Special Swine Flu Update”
  11. article: “Swine Flu: Eight Myths That Could Endanger Your Life”
  12. article: CDC’s Questions and Answers: “Vaccine against 2009 H1N1 Influenza Virus”
  13. Mercola article: “Squalene: The Swine Flu Vaccine’s Dirty Little Secret Exposed”
  14. Mercola article: “Flu Vaccine Exposed”
  15. Mercola article: “CBS Reveals That Swine Flu Cases Seriously Overestimated”
  16. Natural News article: “Ten Swine Flu Lies Told by the Mainstream Media”
  17. Mercola article: “Expert Pediatrician Exposes Vaccine Myths”
  18. WebMD article: “Swine Flu FAQ”
  19. Natural News article: “”Vaccine Revolt! Swine Flu Vaccine Support Crumbles”
  20. “Fact sheet” from the Arizona government’s news release on H1N1

Not very inspiring, is it?

Now there’s inadequate information in the paper to evaluate how accurately the survey method used tracked actual sites shared. But based on the methodology used, articles questioning the safety of the H1N1 vaccine were circulated widely, and anti-vaccine articles and sources dominated.

Are the anti-vaccine tactics effective?

If we accept that decisions to vaccinate are based on an evaluation of the risks of both commission and omission, then we should ask if exposure to anti-vaccine information has a meaningful impact on perceptions of the safety of vaccines. There is some literature that has studied this question. An interesting paper published earlier this year by Betsch and colleagues set out to prospectively measure the impact of anti-vaccination websites. They recruited 517 internet users (from sites for parents or those interested in medical information) and compared risk judgment and vaccination intentions before and after viewing different websites. (The evaluation was in German and used German websites. ) Users were directed to view a vaccine-critical website, or a neutral website, and then evaluated again.  The authors found that viewing anti-vaccine material for only five to ten minutes increased the perception of risk of vaccination, and decreased the perception of risk of omitting vaccines, compared to viewing neutral websites. It also lowered vaccination intentions.

Overwhelmingly, policy analyses of the anti-vaccine movement have centered on the need to address fears by providing reliable, accurate understandable information. But if H1N1 taught us anything, it’s that traditional public health advocacy and messaging is probably insufficient to deal with anti-vaccine tactics used today. We believe that providing the facts alone will be effective, but this tactic is probably ineffective when responding to unfounded fears. Providing factual information, and correcting misinformation needs to be at the core of our advocacy, but it alone does not address the strategies used by anti-vaccine advocates.  It’s the reality we need to accept if we’re going to effectively counter these messages.


One of the biggest drivers of health behaviors is risk perceptions. Anti-vaccine information effectively shapes this, and science advocates need more effective responses. The opportunity to get a real-time understanding of popular anti-vaccine sentiment could help us improve our responsiveness. But unless we focus on prospectively influencing the key factors that drive decisions about vaccination, we’ll continue to struggle.




Posted by Scott Gavura