Neutralisation titres against SARS-CoV-2 are sustained 6 months after onset of symptoms in individuals with mild COVID-19

Background: Given the importance of neutralising antibodies in protection against SARS-CoV-2 infection, it is critical to assess neutralisation persistence long-term following recovery. This study investigated neutralisa-tion titres against SARS-CoV-2 up to 6 months post-symptom onset in individuals with mild COVID-19. Methods: Plasma neutralisation titres in convalescent COVID-19 individuals were determined at baseline and 6 months post-symptom onset using a cell culture infectious SARS-CoV-2 assay. Total SARS-CoV-2 spike-spe-cific IgG and IgA binding was measured using a lectin capture ELISA and compared between timepoints and correlated to neutralising titres. Findings: All 48 convalescent COVID-19 individuals were found to have detectable SARS-CoV-2 50% inhibitory dilution neutralisation titres (ID50) at baseline and 6 months post-symptom onset with mean ID50 of 1/943 and 1/411, respectively. SARS-CoV-2 neutralisation titres peaked within 1-2 months post-symptom onset. However, 50% of individuals showed comparable ID50 at baseline and 6 months post-symptom onset. Both SARS-CoV-2 spike-specific IgG and IgA levels correlated well with neutralising titres. IgG binding was found to be sustained up to 6 months post-symptom onset, whereas IgA levels declined. Interpretation: This study demonstrates durability of SARS-CoV-2 spike-specific IgG and neutralisation responses following recovery from mild COVID-19. Thus, all subjects included in this study might potentially have protective levels of neutralising antibodies 6 months post-symptom onset. This study also demonstrates a relationship between spike-specific IgA and neutralisation decline, with implications for long-term protec-tion against SARS-CoV-2 infection. Funding: Novo Nordisk Foundation, Independent Research Fund Denmark and Danish Agency for Science and Higher Education. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Automated summary

This study found that neutralizing antibodies and spike-specific IgG can persist for up to 6 months following recovery from mild COVID-19, with neutralization titers correlated to levels of IgG and IgA.