COVID-19

Google Trends keyward search volume data are digital biomarkers at population level
Google Trends keyword search volume has emerged as a reliable and accessible tool in prior studies for investigating public interests and behaviors. Unlike traditional methods, it features broad and timely passive data collection with high temporal resolution. Collecting these “footprints” left by search engine users around the globe, the data serve an effective tool for analyzing population-level trends. To understand impact of certain events (e.g. a pandemic outbreak or related policy), we took a counter-factual measure, using ARIMA (autoregressive integrated moving average) modeling to forecast expected search volume for a keyword if a particular event had not occurred (Hyndman & Khandakar, 2008). This forecasted, “expected” data is then compared to the observed search volume during the time period when the event did occur. The difference between the observed and expected volumes suggests the impact of the event on search behavior for that keyword (Y. H. Lin, T. W. Chiang, et al., 2020), which is deemed as a digital biomarker for such events at population level.

Stay-at-home behavior is the major mediating factor of COVID-19 pandemic’s impact on mental health

The extent of stay-at-home behavior, as calculated from cell phone location data in public databases, is a significant mediator of the impact of pandemic severity on mental health. Previous research by our team has identified the search volume for the keyword “insomnia” as the most sensitive indicator of the mental health impact of the COVID-19 pandemic across different countries (Y. H. Lin, T. W. Chiang, et al., 2020). In this study, we used the search volume of “insomnia” and “suicide” as mental health indicators, and discovered that the degree of staying at home played the most important mediating role in the impact of pandemic severity on mental health.

We also demonstrated the dynamic nature of the mediation effect of stay-at-home behavior. For example, in the first six months of the pandemic, the degree of staying at home had a significant mediating effect on the increase in insomnia (PM = 42.6 %, p=0.016), but not on suicidality (PM = 8.1 %, p=0.180); in the second half of the year, it had a significant mediating effect on the decrease in suicide (PM = 39.6%, p=0.014) but not on insomnia (PM = 13.1 %, p=0.270) As the pandemic progresses, these findings provide an essential empirical basis for potential flexible adjustments to stay-at-home policies, especially when vaccines and antiviral drugs become widely available. These adjustments could be informed by the potential impact of staying at home on population mental health.

COVID-19 vaccine willingness transformation followed local epidemic outbreaks in Taiwan

The search volume for the keyword “vaccine” on the internet can reflect and continuously track the public’s willingness to get vaccinated. Traditional survey methods cannot provide comprehensive and continuous data with high time resolution. This study uses Google Trends data from March 19, 2021, to May 25, 2021, to examine changes in search volume for the keyword “vaccine” in Taiwan during the period from the start of the vaccination campaign at the end of March last year to the subsequent outbreak of local COVID-19 cases in May, to study the public’s willingness to get vaccinated. We found that the Google search volume for “vaccine” was highly correlated with the number of confirmed local infections (r=0.71, P<.001). We clearly observed that a crucial factor influencing Taiwanese people’s willingness to be vaccinated is the local epidemic situation.

The public’s willingness to get vaccinated changed continuously with the progression of the epidemic. Over the analyzed period, the search volume for “vaccine” and related keywords corresponded to the different stages in the Transtheoretical Model of behavior change — Precontemplation, Contemplation, and Decision/Action (Norcross et al., 2011). Precontemplation: This stage refers to the period before the small-scale COVID-19 outbreak in Taiwan (March 19 – April 19, 2021).
Despite the availability of vaccines, both the search volume for “vaccine” and vaccination rates were low, indicating that most people were not yet considering vaccination. Contemplation: During the small-scale outbreak (April 20 – May 11, 2021), search volume and vaccination rates increased, suggesting that people were becoming aware of the threat of COVID-19 and beginning to weigh the risks and benefits of vaccination. This is reflected by the most popular related search query being “side effects ” of vaccination. Decision/Action: The large-scale outbreak (May 12 – May 25, 2021) was marked by a significant increase in both search volume for “vaccine” and national vaccination rates. Related search queries focused on “vaccine appointments” and information about the AstraZeneca vaccine, the only vaccine available in Taiwan at that time, suggesting people were actively seeking vaccination. These findings suggest that real-time monitoring of internet search trends can provide valuable insights into public health concerns like vaccine hesitancy and help inform targeted interventions.

National Policies and Containment of COVID-19 Pandemic

By monitoring collective digital footprints from open databases, we also made contributions to assessing the effectiveness of COVID-19 containment policies. We used search volume data from Google Trends for “wash hands,” “face mask,” and “insomnia” as indicators of national population health literacy and mental health trends in one study that evaluated COVID-19 policies over 50 countries or territories in the first 2 year of the pandemic. Including the Google Trends indicator for health literacy and insomnia in the sensitivity analysis slightly altered the overall containment performance rankings of the 50 countries examined in the study, suggesting that public interest and search behavior related to these terms provides valuable insights into a nation’s pandemic preparedness and response (Tsou et al., 2022). 

In another study, Google mobility reports were leveraged to see how people’s movements and gatherings changed in response to different COVID-19 alert levels and policy interventions in Taiwan. It was shown that crowds in retail sites, recreation sites, parks, transit stations, and workplaces in Taiwan declined significantly after the Taipei City and New Taipei City Level-3 alerts. Then when the Level-3 COVID-19 alert was implemented throughout Taiwan on May 15, 2021, the average number of daily trips dropped sharply, particularly in urban areas. Taipei City saw a 52% reduction in daily trips, with an average decrease of 28% for all cities. This decline in movement, both before and after strict lockdown measures, indicated that people in Taiwan chose to limit their activities and gatherings as a precaution. 

Lastly, despite the emergence of the Omicron variant in early 2022, low hospitalization and death rates persisted in Taiwan, and people continued with their normal lives as seen in Google mobility reports. This suggested that the public health measures and public response in Taiwan have been successful in mitigating the impact of the Omicron variant (Tsou et al., 2024). Google Trends data served as a valuable proxy for understanding population behavior and sentiments that are not easily captured through traditional survey methods. These digital footprints helped gaining a more comprehensive understanding of the public’s response to the pandemic and the effectiveness of different policies and interventions.

Publications

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