The World Health Organization's public health intelligence activities during the COVID-19 pandemic response, December 2019 to December 2021

The coronavirus disease (COVID-19) presented a unique opportunity for the World Health Organization (WHO) to utilise public health intelligence (PHI) for pandemic response. WHO systematically captured mainly unstructured information (e.g. media articles, listservs, community-based reporting) for public health intelligence purposes. WHO used the Epidemic Intelligence from Open Sources (EIOS) system as one of the information sources for PHI. The processes and scope for PHI were adapted as the pandemic evolved and tailored to regional response needs. During the early months of the pandemic, media monitoring com-plemented official case and death reporting through the International Health Regulations mechanism and triggered alerts. As the pandemic evolved, PHI activi-ties prioritised identifying epidemiological trends to supplement the information available through indica-tor-based surveillance reported to WHO. The PHI scope evolved over time to include vaccine introduction, emergence of severe acute respiratory syndrome coro-navirus 2 (SARS-CoV-2) variants, unusual clinical man-ifestations and upsurges in cases, hospitalisation and death incidences at subnational levels. Triaging the unprecedented high volume of information challenged surveillance activities but was managed by collabora-tive information sharing. The evolution of PHI activi-ties using multiple sources in WHO's response to the COVID-19 pandemic illustrates the future directions in which PHI methodologies could be developed and used.