AUTHOR=Neeland Melanie R. , Bannister Samantha , Clifford Vanessa , Nguyen Jill , Dohle Kate , Overmars Isabella , Toh Zheng Quan , Anderson Jeremy , Donato Celeste M. , Sarkar Sohinee , Do Lien Anh Ha , McCafferty Conor , Licciardi Paul V. , Ignjatovic Vera , Monagle Paul , Bines Julie E. , Mulholland Kim , Curtis Nigel , McNab Sarah , Steer Andrew C. , Burgner David P. , Saffery Richard , Tosif Shidan , Crawford Nigel W. TITLE=Children and Adults in a Household Cohort Study Have Robust Longitudinal Immune Responses Following SARS-CoV-2 Infection or Exposure JOURNAL=Frontiers in Immunology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.741639 DOI=10.3389/fimmu.2021.741639 ISSN=1664-3224 ABSTRACT=

Children have reduced severity of COVID-19 compared to adults and typically have mild or asymptomatic disease. The immunological mechanisms underlying these age-related differences in clinical outcomes remain unexplained. Here, we quantify 23 immune cell populations in 141 samples from children and adults with mild COVID-19 and their PCR-negative close household contacts at acute and convalescent time points. Children with COVID-19 displayed marked reductions in myeloid cells during infection, most prominent in children under the age of five. Recovery from infection in both children and adults was characterised by the generation of CD8 TCM and CD4 TCM up to 9 weeks post infection. SARS-CoV-2-exposed close contacts also had immunological changes over time despite no evidence of confirmed SARS-CoV-2 infection on PCR testing. This included an increase in low-density neutrophils during convalescence in both exposed children and adults, as well as increases in CD8 TCM and CD4 TCM in exposed adults. In comparison to children with other common respiratory viral infections, those with COVID-19 had a greater change in innate and T cell-mediated immune responses over time. These findings provide new mechanistic insights into the immune response during and after recovery from COVID-19 in both children and adults.