Antibody levels remain high to one-year's follow-up after moderate and severe COVID-19, but not after mild cases

Infect Dis (Lond). 2022 May;54(5):345-355. doi: 10.1080/23744235.2021.2018492. Epub 2021 Dec 24.

Abstract

Background: Understanding the longevity of antibodies against SARS-CoV-2 infection is of utmost importance in predicting the further course of the pandemic and to plan vaccination strategies. Here we report a cohort of COVID-19 patients with different disease severities whose antibody dynamics we evaluated during one-year of follow-up.

Methods: We conducted a longitudinal study of 123 COVID-19 patients and 45 SARS CoV-2 negative outpatients with upper respiratory tract infection. We analyzed the demographic and clinical features of the patients with COVID-19 in relation to different disease severities according to the WHO classification. The antibody response was evaluated by a Luciferase Immunoprecipitation System (LIPS) assay at 3, 6, and 12 months after the acute infection.

Results: Amongst the enrolled COVID-19 patients, 15 (12%) had mild, 42 (34%) had moderate, 39 (32%) had severe and 27 (22%) had critical disease courses; 79% of the patients were hospitalized. During follow-up, all patients had anti-SARS RBD-IgG levels above the cut-off value on all visits, but the antibody levels varied significantly between the different disease severity groups. Between the six- and 12-month follow-up visits, 41% of patients were vaccinated, which enhanced their antibody levels significantly.

Conclusion: Our data demonstrate sustained antibody levels at one-year after moderate and severe COVID-19 infection. Vaccination of patients with the mild disease is important to raise the antibody levels to a protective level.

Keywords: COVID-19; RBD-IgG antibodies; SARS CoV-2; one-year follow-up; the WHO classification; vaccination.

MeSH terms

  • Antibodies, Viral
  • COVID-19*
  • Follow-Up Studies
  • Humans
  • Immunoglobulin G
  • Longitudinal Studies
  • SARS-CoV-2

Substances

  • Antibodies, Viral
  • Immunoglobulin G

Grants and funding

The study was supported by the basic research fund of the Department of Internal Medicine, Institute of Clinical Medicine of University of Tartu and by RITA2/126 (HOSPICOVI) a project financed by the Estonian Research Council.