biostudies-literatureUnknownBents SJNIAID NIH HHSWellcome TrustThe rebound of endemic respiratory viruses following the COVID-19 pandemic was marked by atypical transmission dynamics, with children experiencing increased disease burden and out-of-season epidemics as restrictions relaxed. Here we used serology from a newly developed quantitative multiplex assay to assess the post-pandemic immunity debt, a drop in immunity due to a lack of endemic virus circulation during COVID-19. We assessed age-specific antibody dynamics in Seattle, Washington, US, across a broad range of respiratory viruses, including influenza, respiratory syncytial virus, seasonal coronaviruses, and SARS-CoV-2. We found that respiratory virus immunodynamics differed between individuals <5 years of age and older individuals, with young children experiencing both larger boosts and qmedRxiv : the preprint server for health sciences2025.03.26.25324738https://www.ebi.ac.uk/biostudies/studies/S-EPMC12478342biostudies-literatureMultiplex serology reveals age-specific immunodynamics of endemic respiratory pathogens in the wake of the COVID-19 pandemic.PMC1247834275N93021C00015225001/Z/22/ZHansen CBlazevic RHan PBents SJSteven-Ayers TWaghmare AAndrews CKimball LEnglund JABoeckh MStarita LAdler APerofsky AWolter NPrentice RMoyes JMartin ETKrantz EMViboud Cvon Gottberg ACohen CHay JAMaake LfalseMultiplex serology reveals age-specific immunodynamics of endemic respiratory pathogens in the wake of the COVID-19 pandemic.The rebound of endemic respiratory viruses following the COVID-19 pandemic was marked by atypical transmission dynamics, with children experiencing increased disease burden and out-of-season epidemics as restrictions relaxed. Here we used serology from a newly developed quantitative multiplex assay to assess the post-pandemic immunity debt, a drop in immunity due to a lack of endemic virus circulation during COVID-19. We assessed age-specific antibody dynamics in Seattle, Washington, US, across a broad range of respiratory viruses, including influenza, respiratory syncytial virus, seasonal coronaviruses, and SARS-CoV-2. We found that respiratory virus immunodynamics differed between individuals <5 years of age and older individuals, with young children experiencing both larger boosts and q2025-01-01T00:00:00Z2025 Mar2026-07-01T03:09:23.537Z2026-07-01T03:07:36.586ZS-EPMC124783424103092910.1101/2025.03.26.25324738