SARS-CoV-2–specific B- and T-cell immunity in a population-based study of young Swedish adults

• Published in: Journal of allergy and clinical immunology Vol. 149; no. 1; pp. 65 - 75.e8
• Main Authors: Björkander, Sophia, Du, Likun, Zuo, Fanglei, Ekström, Sandra, Wang, Yating, Wan, Hui, Sherina, Natalia, Schoutens, Lisanne, Andréll, Juni, Andersson, Niklas, Georgelis, Antonios, Bergström, Anna, Marcotte, Harold, Kull, Inger, Hammarström, Lennart, Melén, Erik, Pan-Hammarström, Qiang, Almqvist, Catarina, Ballardini, Natalia, Brodin, Petter, Castel, Anna, Hallberg, Jenny, Jansson, Christer, Kere, Maura, Lauber, André, Lövquist, Alexandra, Mjösberg, Jenny, Mogensen, Ida, Palmberg, Lena, Pershagen, Göran, Roxhed, Niclas, Schwenk, Jochen
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2022; The Authors. Published by Elsevier Inc. on behalf of the American Academy of Allergy, Asthma & Immunology
• Subjects: Adult; Antibodies, Viral - immunology; asthma; Birth Cohort; Covid-19; COVID-19 - immunology; COVID-19 disease; Female; Follow-Up Studies; Humans; IgA; IgG; IgM; Immunity, Cellular; Immunity, Humoral; Male; mem-ory T cells; memory B cells; Memory B Cells - immunology; memory T cells; population-based cohort; Prospective Studies; risk factors; SARS-CoV-2; SARS-CoV-2 - immunology; Sweden; T-Lymphocytes - immunology; young adults; Sweden; BAMSE; IgA; risk factors; S N M O; IgG; asthma; memory B cells; PBMC; IgM; memory T cells; COVID-19; SARS-CoV-2; RBD; young adults; COVID-19 disease; population-based cohort; S1; WHO
• DOI: 10.1016/j.jaci.2021.10.014
• ISSN: 0091-6749; 1097-6825

Young adults are now considered major spreaders of coronavirus disease 2019 (COVID-19) disease. Although most young individuals experience mild to moderate disease, there are concerns of long-term adverse health effects. The impact of COVID-19 disease and to which extent population-level immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exists in young adults remain unclear. We conducted a population-based study on humoral and cellular immunity to SARS-CoV-2 and explored COVID-19 disease characteristics in young adults. We invited participants from the Swedish BAMSE (Barn [Children], Allergy Milieu, Stockholm, Epidemiology) birth cohort (age 24-27 years) to take part in a COVID-19 follow-up. From 980 participants (October 2020 to June 2021), we here present data on SARS-CoV-2 receptor-binding domain–specific IgM, IgA, and IgG titers measured by ELISA and on symptoms and epidemiologic factors associated with seropositivity. Further, SARS-CoV-2–specific memory B- and T-cell responses were detected for a subpopulation (n = 108) by ELISpot and FluoroSpot. A total of 28.4% of subjects were seropositive, of whom 18.4% were IgM single positive. One in 7 seropositive subjects was asymptomatic. Seropositivity was associated with use of public transport, but not with sex, asthma, rhinitis, IgE sensitization, smoking, or body mass index. In a subset of representative samples, 20.7% and 35.0% had detectable SARS-CoV-2 specific B- and T-cell responses, respectively. B- and T-cell memory responses were clearly associated with seropositivity, but T-cell responses were also detected in 17.2% of seronegative subjects. Assessment of IgM and T-cell responses may improve population-based estimations of SARS-CoV-2 infection. The pronounced surge of both symptomatic and asymptomatic infections among young adults indicates that the large-scale vaccination campaign should be continued.