What can social media tell us about vaccination rates?

Gary Finnegan

Gary Finnegan

October 27th, 2011

Gary Finnegan

TwitterTwitter, looks set to become fertile study ground for academics and health officials interested in tracking attitudes to immunisation.

Social media networks can help identify geographic clusters of unvaccinated individuals and serve as a window on the ebbs and flows of public opinion, according to a new study by researchers at Penn State University in the United States.

Around 150 million tweets are published by Twitter every day, providing a massive volume of information on everything from health and politics to pop music and celebrity gossip.

Read: Twitter: the new flu-tracking tool?

In an effort to understand public sentiment during the 2009 H1N1 flu pandemic, Marcel Salathé, an assistant professor of biology, sifted through almost 500,000 tweets sent during the peak of the outbreak.

He then looked at how users’ views corresponded with vaccination rates and how microbloggers using Twitter appeared to influence those in their online social circle.

The results, which will be published in the journal PLoS Computational Biology, revealed a number of clear patterns which linked online sentiment with offline behaviour.

People in New England, in the north east of the US, were found to have the most positive views of H1N1 vaccination and this region also had the highest rates of immunisation against the pandemic flu strain.

“These results could be used strategically to develop public-health initiatives,” Salathé explained. “For example, targeted campaigns could be designed according to which region needs more prevention education. Such data also could be used to predict how many doses of a vaccine will be required in a particular area.”

The immunity herd

The researchers were also able to construct complex social networks by looking at connections between Twitter users such as who follows whom. This put the spotlight on clusters of users who tended to surround themselves online with like-minded people – turning Twitter into a personal echo-chamber.

The implications of this, Salathé said, is that if anti-vaccination communities also cluster in real, geographic areas “this is likely to lead to under-vaccinated communities that are at great risk of local outbreaks.”

“By definition, herd immunity only works if unvaccinated, unprotected individuals are distributed sparsely throughout the population, buffered from the disease by vaccinated individuals. Unfortunately, the data from Twitter seem to indicate that the buffer of protection cannot be counted on if these clusters exist in real, geographical space.”

Tracking the trends

Following online public sentiment through time showed how negative opinions spiked during times when batches of vaccine were recalled, while positive views dominated when the vaccine was first shipped across the US easing public worries about being infected by the virus.

The researchers believe that following public opinion Twitter and other social media channels should become a part of media monitoring by public health promotion bodies. But it need not stop at vaccines. Opinions on infectious diseases could also be studied via Twitter, according to academics.

“Now that heart disease – a malady caused, at least in part, by lifestyle – is moving to the top of the list of killers, it might be wise to focus on how social media influences behaviours such as poor diet and infrequent exercise,” Salathé said.

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