While the efficacy of vaccines to prevent disease has been proven many times over, new research has taken a particularly interesting approach: analyzing Google searches. Researchers have compared online inquiries for information about chickenpox symptoms and country vaccination policies.
By finding correlations between the searcheses of thousands of people and the timing of seasonal outbreaks, the new study shows that Google searches for the common childhood disease drop sharply following mandatory vaccinations.
The technique of analyzing data to understand real-world disease outbreaks is called digital epidemiology, and is becoming more common, identifying instances of influenza and rotovirus, for instance — and this study is the first that's proven the effectiveness of a vaccine.
Researchers at the University of Michigan analyzed Google Trends data culled from 2004 to 2015, examining results spanning three dozen countries and five continents. And since chickenpox has such idiosyncratic symptoms, rather than broadly applicable ones like coughs or rashes, the scientists behind the study were able to link the disease and the online activity with a high level of confidence.
"These results demonstrate that if you institute nationwide vaccination for chickenpox there is a very clear reduction in searches," said doctoral student and study lead author Kevin Bakker in a press release announcing the findings, "which is a way to infer a strong reduction in total disease incidence."
The researchers also found that by analyzing the Google searches for "chickenpox" in countries that require reporting but not vaccinations — places like Thailand, Mexico and Estonia — a forecasting model could predict outbreak timing and magnitude.
The scientists say that the data from Germany was particularly revealing, as that country did not roll out a large vaccination plan at one time, but instead gradually increased implementation over years — and the searches for information about chickenpox symptoms decreased over time as the vaccine program grew extended its reach.
"It is really exciting to see human information-seeking behavior — Google searches — being reduced by vaccination implementation," said Bakker. "It's a very clear signal, and it shows that the vaccine is having a strong effect."