Viruses are ubiquitous pathogens that cause innumerable infections each year in humans. Many infections are sub-clinical or only result in mild symptoms, while some result in serious clinical illness. There is a well recognised seasonality to many viruses and there is a complex interaction between behaviour, exposure, season, and circulating strains that means that viral epidemiology is complex. VirScan is a new technique that allows for simultaneous measurement of exposure to all known human viruses in a single human sample. This technique means that we can identify the 'infection history' of a given individual based on one serum sample. In this proposal, we aim to use this VirScan technology to profile the response of ALSPAC participants to viruses over the period of the COVID-19 pandemic. This will allow us unique insight to the changes in viral epidemiology over this time period, and answer key questions about the durability of infection response and how viral epidemiology changed over this time period. A comparator analysis will be performed in TwinsUK to compare and contrast.