Antibody persistence and neutralising activity in primary school students and staff: prospective active surveillance, June to December 2020, England

Ireland, G.; Jeffery-Smith, A. J.; Zambon, M. J.; Hoschler, K.; Harris, R. J.; Poh, J.; Baawuah, F.; Beckmann, J. J.; Okike, I. O.; Ahmad, S.; Garstang, J.; Brent, A. J.; Brent, B.; Aiano, F.; Amin-Chowdhury, Z.; Letley, L.; Jones, S. E.; Kall, M.; Patel, M.; Gopal, R.; Borrow, R.; Linley, E.; Amirthalingam, G.; Brown, K. E.; Ramsay, M. E.; Ladhani, S. N.

Introduction SARS-CoV-2 serological studies have so far focused mainly on adults. Public Health England initiated prospective, longitudinal SARS-CoV-2 sero-surveillance in schools across England after the first national lockdown, which allowed comparison of child and adult responses to SARS-CoV-2 infection over time. Methods Staff and students had venepuncture for SARS-CoV-2 antibodies in school during June, July and December 2020. Blood samples were tested for nucleocapsid (Abbott) and receptor binding domain (RBD) antibodies (in-house assay), and student samples were additionally assessed for live virus neutralising activity. Results In June 2020, 1,344 staff and 835 students were tested. Overall, 11.5% (95% CI: 9.4-13.9) and 11.3% (95% CI: 9.2-13.6; p=0.88) of students had nucleoprotein and RBD antibodies, compared to 15.6% (95% CI: 13.7-17.6) and 15.3% (95% CI: 13.4-17.3; p=0.83) of staff. Live virus neutralising activity was detected in 79.8% (n=71/89) of nucleocapsid and 85.5% (71/83) of RBD antibody positive children. RBD antibodies correlated more strongly with neutralising antibodies (rs=0.7527; p<0.0001) than nucleocapsid antibodies (rs=0.3698; p<0.0001). A median of 24.4 weeks later, 58.2% (107/184) participants had nucleocapsid antibody seroreversion, compared to 20.9% (33/158) for RBD (p<0.001). Similar seroreversion rates were observed between staff and students for nucleocapsid (p=0.26) and RBD-antibodies (p=0.43). Nucleocapsid and RBD antibody quantitative results were significantly lower in staff compared to students (p=0.028 and <0.0001 respectively) at baseline, but not at 24 weeks (p=0.16 and p=0.37, respectively). Conclusion RBD antibodies correlated more strongly with live virus neutralising activity. Most seropositive students and staff retained RBD antibodies for >6 months after SARS-CoV-2 infection.