Antibody kinetics to SARS-CoV-2 at 13.5 months, by disease severity

Violan, C.; Toran, P.; Quirant, B.; Lamonja-Vicente, N.; Carrasco-Ribelles, L. A.; Chacon, C.; Manresa-Dominguez, J. M.; Ramos-Roure, F.; Roso-Llorach, A.; Pujol, A.; Ouchi, D.; Monteagudo, M.; Montero, P.; Garcia-Sierra, R.; Armestar, F.; Dacosta-Aguayo, R.; Dolade, M.; Prat, N.; Bonet, J. M.; Clotet, B.; Blanco, I.; Prado, J. G.; Martinez-Caceres, E. M.; Investigators, ProHEpiC-19

Background: Understanding humoral responses and seroprevalence in SARS-CoV-2 infection is essential for guiding vaccination strategies in both infected and uninfected individuals. Methods: We determine the kinetics of IgM against the nucleocapsid (N) and IgG against the spike (S) and N proteins of SARS-CoV-2 in a cohort of 860 health professionals (healthy and infected) in northern Barcelona. We model the kinetics of IgG and IgM at nine time points over 13.5 months from infection, using non-linear mixed models by sex and clinical disease severity. Results: Of the 781 participants who were followed up, 478 (61.2%) became infected with SARS-CoV-2. Significant differences were found for the three antibodies by disease severity and sex. At day 270 after diagnosis, median IgM(N) levels were already below the positivity threshold in patients with asymptomatic and mild-moderate disease, while IgG(N, S) levels remained positive to days 360 and 270, respectively. Kinetic modelling showed a general rise in both IgM(N) and IgG(N) levels up to day 30, followed by a decay whose rate depended on disease severity. IgG(S) levels increased at day 15 and remained relatively constant over time. Conclusions: We describe kinetic models of IgM(N) and IgG(N, S) SARS-CoV-2 antibodies at 13.5 months from infection and disease spectrum. Our analyses delineate differences in the kinetics of IgM and IgG over a year and differences in the levels of IgM and IgG as early as 15 days from symptoms onset in severe cases. These results can inform public health policies around vaccination criteria.