The ongoing value of first few X studies for COVID-19 in the Western Pacific Region


Adrian J Marcato, James E Fielding, Kristy Crooks, Peter D Massey, Linh-Vi Le, Isabel Bergeri, Jodie McVernon

Western Pacific Surveillance and Response Journal, published online 24 March 2022. DOI:

Studies of the first few “X” (FFX) – formerly known as “First Few 100” – cases involve rapid collection of data and specimens from the cases of a novel pathogen or emerging variants and their close contacts. Collection of standardized high-quality clinical, epidemiological, virological and serological data in FFX studies can provide insight into transmission dynamics, severity, risk factors for severe disease and the clinical spectrum of disease. These data can be used in risk assessment and modelling studies, to forecast potential impact and guide preparedness planning and public health interventions.

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