OBJECTIVES: The COVID-19 pandemic disrupted the incidence of pediatric infections, including varicella. Due to limited surveillance data, the impact of the pandemic on varicella incidence patterns across Europe remains unknown. This study aims to describe Google search query trends for varicella-related keywords in Europe as a proxy to varicella incidence before and during the COVID-19 pandemic in countries with/without universal varicella vaccination (UVV).

METHODS: Country-specific varicella-related monthly search query data (relative search popularity and absolute search volume) was extracted from Google Trends/Google Ads between 2015-2021 and used to describe search trends over time. Search query data was used to describe search intensity before (until February 2020) and during the COVID-19 pandemic (March 2020-December 2021). European countries were further stratified by the UVV status.

RESULTS: In countries with no UVV, search intensity for varicella-specific keywords showed high seasonal variation and peaked between October-January and March-June months in line with commonly observed peaks of varicella infection in Europe. Although approaching the peak in March 2020, the search intensity dropped dramatically (-33% to -70%) at the start of the pandemic (April 2020) and remained low until mid-2021. Information seeking behavior started to increase in second half of 2021 and continued to grow beyond the pre-pandemic level until December 2021 indicating a potential rebound. In countries with established UVV, peaks in search intensity and the pandemic impact were less pronounced than in countries with no UVV.

CONCLUSIONS: Using digital language-specific search query data as a proxy for varicella incidence, we demonstrated that the COVID-19 pandemic substantially disrupted the incidence of varicella, especially in countries with no UVV. This may result in a substantial share of individuals not acquiring natural immunity leading to potential outbreaks. Digital search query data could be considered as an effective tool to assess dynamics in varicella incidence, especially in countries without good surveillance systems.