Longitudinal study of humoral immunity against SARS-CoV-2 of health professionals in Brazil: the impact of booster dose and reinfection on antibody dynamics

Front Immunol. 2023 Jul 14:14:1220600. doi: 10.3389/fimmu.2023.1220600. eCollection 2023.

Abstract

Introduction: The pandemic caused by SARS-CoV-2 has had a major impact on health systems. Vaccines have been shown to be effective in improving the clinical outcome of COVID-19, but they are not able to fully prevent infection and reinfection, especially that caused by new variants.

Methods: Here, we tracked for 450 days the humoral immune response and reinfection in 52 healthcare workers from Brazil. Infection and reinfection were confirmed by RT-qPCR, while IgM and IgG antibody levels were monitored by rapid test.

Results: Of the 52 participants, 19 (36%) got reinfected during the follow-up period, all presenting mild symptoms. For all participants, IgM levels dropped sharply, with over 47% of them becoming seronegative by the 60th day. For IgG, 90% of the participants became seropositive within the first 30 days of follow-up. IgG antibodies also dropped after this period reaching the lowest level on day 270 (68.5 ± 72.3, p<0.0001). Booster dose and reinfection increased the levels of both antibodies, with the interaction between them resulting in an increase in IgG levels of 130.3 arbitrary units.

Conclusions: Overall, our data indicate that acquired humoral immunity declines over time and suggests that IgM and IgG antibody levels are not associated with the prevention of reinfection.

Keywords: COVID-19; SARS-COV-2; antibody; healthcare workers; humoral immunity; reinfection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brazil / epidemiology
  • COVID-19*
  • Health Personnel
  • Humans
  • Immunity, Humoral*
  • Immunoglobulin G
  • Immunoglobulin M
  • Longitudinal Studies
  • Reinfection
  • SARS-CoV-2

Substances

  • Immunoglobulin G
  • Immunoglobulin M

Grants and funding

This research was funded by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) (Grant number: APQ-00635-20) and the Fundação Oswaldo Cruz – Inova Program (Grant number: VPPCB-005-FIO-20-2-24) and CNPq (Fellowship Grant number: CTF- 306188/2022-8).