By Stephanie Pappas, Senior Writer
Published: 02/11/2014 07:05 PM EST on LiveScience
In a purely rational world, vaccination rates would vacillate constantly depending on how much people fear getting sick.
That's what attempts to model vaccination rates mathematically have found. But now, scientists have added in the missing puzzle piece that explains why vaccination rates stay high in the real world — or, in some cases, low. The reason, it turns out, is peer pressure.
Public health officials frequently worry about low levels of childhood vaccination, often driven by debunked concerns that vaccines are linked with autism. But in many nations without mandatory vaccination rules, rates of childhood vaccination remain surprisingly high, said Tamer Oraby, a mathematician at the University of Guelph in Ontario, Canada. [5 Dangerous Vaccination Myths]
"The question we wanted to answer is, 'Why are we seeing such high vaccination levels in nonmandatory vaccination programs?'" Oraby told Live Science.
Mathematical models had predicted that as vaccination eliminates the day-to-day occurrence of measles, mumps, rubella, whooping cough (pertussis) and other childhood diseases, parents would opt out of vaccinating their kids due to a perception that the risk of catching a disease is low. Yet in countries such as Italy, the United Kingdom, Portugal and Finland, vaccination rates remain high enough to keep these diseases down, despite no mandatory vaccination laws, Oraby and his colleagues wrote today (Feb. 11) in the journal Proceedings of the Royal Society B.
Drawing on research from public health and sociology, the researchers suspected that social pressures might explain relatively high and steady vaccination rates. They created a mathematical model in which virtual "individuals" could choose to vaccinate their children or not. These individuals constantly surveyed the rest of the actors in the model, and when they saw one making a choice with a greater survival payoff — for instance, vaccinating versus not — they swapped to the more advantageous strategy.
Then, the researchers added another factor: The more people chose a strategy, the greater the benefit of that strategy. This addition to the model mimicked peer pressure, in which people benefit from fitting in with their social group.
The resulting model fit real-world observations of vaccination choices, Oraby and his colleagues found. Social norms can keep vaccination rates high even in the absence of obvious disease risk.
But peer pressure is a double-edged sword, Oraby said. After a vaccine "scare," in which people become convinced that vaccines carry a major risk (such as autism), social norms keep vaccination rates depressed long after the scare ends, the model showed. This fits with observations seen in the United Kingdom in the 1970s, when an unsubstantiated scare over the side effects of the whooping-cough vaccine, Oraby said. The scare led to a drop in vaccination that created two whooping-cough outbreaks, each of which affected 400,000 children, according to U.K. health information site Patient.co.uk.
Fears of autism, driven by a fraudulent 1998 study linking the MMR (measles, mumps and rubella) vaccine to the disorder, have pushed MMR vaccination rates below the ideal 90 percent in 15 U.S. states, according to the Centers for Disease Control and Prevention.
"In short, it's because people underestimate the risk of the disease and overestimate the risk of the vaccination," Oraby said.
In the future, Oraby and his colleagues plan to look at what happens when the social pressure not to vaccinate outweighs the pressure to vaccinate, and vice versa. The findings suggest, however, that top-down messages from doctors and public health officials urging people to vaccinate their children may not be enough to keep childhood diseases at bay.
"The message here might be that we need to encourage people to vaccinate in our social networks," Oraby said. "Showing the actual risks of both vaccination and nonvaccination can raise the vaccine acceptance rate."
Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.
Copyright 2014 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. ]]>
Our 2024 Coverage Needs You
It's Another Trump-Biden Showdown — And We Need Your Help
The Future Of Democracy Is At Stake
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
The 2024 election is heating up, and women's rights, health care, voting rights, and the very future of democracy are all at stake. Donald Trump will face Joe Biden in the most consequential vote of our time. And HuffPost will be there, covering every twist and turn. America's future hangs in the balance. Would you consider contributing to support our journalism and keep it free for all during this critical season?
HuffPost believes news should be accessible to everyone, regardless of their ability to pay for it. We rely on readers like you to help fund our work. Any contribution you can make — even as little as $2 — goes directly toward supporting the impactful journalism that we will continue to produce this year. Thank you for being part of our story.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
It's official: Donald Trump will face Joe Biden this fall in the presidential election. As we face the most consequential presidential election of our time, HuffPost is committed to bringing you up-to-date, accurate news about the 2024 race. While other outlets have retreated behind paywalls, you can trust our news will stay free.
But we can't do it without your help. Reader funding is one of the key ways we support our newsroom. Would you consider making a donation to help fund our news during this critical time? Your contributions are vital to supporting a free press.
Contribute as little as $2 to keep our journalism free and accessible to all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you'll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.