Prior studies have shown strong correlation between internet search and public health surveillance data. Less is known about how search data responds to public health interventions, such as vaccination, and the consistency of these responses in different countries. We aim to study the correlation between rotavirus internet searches and rotavirus disease activity in the United States (US), United Kingdom (UK) and Mexico, before and after national rotavirus vaccine introductions.
We compared the time series of internet searches for rotavirus from Google Trends with rotavirus laboratory surveillance data for US and UK, and with acute gastroenteritis hospitalization data from US and Mexico. Using time and location parameters, Google quantifies an Internet Query Share (IQS) to measure the relative search volume for a specific term. We analyzed the correlation between IQS and laboratory and hospitalization data before and after national vaccine introduction (June 2006 in the US, July 2013 in the UK, and May 2007 in Mexico). We fit regression models to account for the contribution of non-rotavirus disease factors (US and UK norovirus laboratory reports and rotavirus vaccine searches) to rotavirus IQS.
There was strong positive correlation between rotavirus IQS and rotavirus laboratory data for the US (R2=0.79) and UK (R2=0.60), and between rotavirus IQS and acute gastroenteritis hospitalization data for the US (R2=0.87) and Mexico (R2=0.69), p<.0001 for all correlations. In all four time series (Figures 1 and 2), correlations were stronger in the pre-vaccine period compared to the post-vaccine period. Mean rotavirus IQS decreased after vaccine introduction by 40% (95% CI: 25-55%) in the US and by 70% (95% CI: 55-86%) in Mexico. In the UK, there was no change in rotavirus IQS, but there was a loss of seasonal variation in rotavirus IQS after vaccine introduction. Adding norovirus laboratory data and rotavirus vaccine IQS improved the fit of the US and UK post-vaccine models to approximate pre-vaccine models.
Rotavirus internet search data trends mirrored national rotavirus laboratory and gastroenteritis hospitalization surveillance data in the US, UK, and Mexico, and demonstrated a decline in public interest following rotavirus vaccine implementation.
J. Tate, None
J. Harris Jr., None
M. Esparza-Aguilar, None
E. Sanchez-Uribe, None
V. Richardson, None
U. D. Parashar, None