Immunoglobulin G follow-up and immune response longevity analysis in SARS-CoV-2 convalescent patients and vaccinated individuals: A longitudinal analysis

Article type: Research Article

Authors: Maki, Fadia Mothafar^{a; *} | AL-Thwani, Anima Namma^a | Jiad, Kareem Shahal^b | Musafer, Karar Nadhum Jawad^c

Affiliations: [a] Genetic Engineering and Biotechnology Institute, University of Baghdad, Baghdad, Iraq | [b] Iraqi Ministry of Health, Baghdad, Iraq | [c] Department of Pharmacy, Al-Zahrawi University College, Karbala, Iraq

Correspondence: [*] Corresponding author: Fadia Mothafar Maki, Genetic Engineering and Biotechnology Institute, University of Baghdad, Baghdad, Iraq. Tel.: +964 7709628674; E-mail: fadia.maki@gmail.com.

Abstract: BACKGROUND: Although the detection of immunoglobulin G (IgG) molecules has long been considered to be crucial for successful humoral immune defence against infections and harmful metabolites, it has become increasingly important in relation to SARS-CoV-2 research. OBJECTIVE: To compare longitudinal changes in IgG titres in post-infection and post-vaccination Iraqi participants, and to estimate the protective benefits of the two principal vaccines used in Iraq. METHODS: This quantitative study used samples from SARS-CoV-2 recovered patients (n= 75), those vaccinated with two doses of Pfizer or Sinopharm vaccine (n= 75), and healthy unvaccinated individuals (n= 50) who formed a control group. Participant ages (range 20–80 years) and sex (52.7% men, 47.3% females). An enzyme-linked immunosorbent assay was used to measure IgG. RESULTS: IgG antibody levels peaked in the first month and tapered off in the following three months in both convalescent and vaccinated groups. The latter showed a significant decrease in IgG titres than in the convalescent group. Samples from the group given the mRNA vaccination that targeted spike (S) proteins might have a cross-reactivity between nucleocapsid (N) and spike (S) proteins. CONCLUSIONS: Participants who had recovered from or who were vaccinated against SARS-CoV-2 exhibited a protective, persistent and durable humoral immune response for at least a month. This was more potent in the SARS-CoV-2 convalescent group compared to the vaccinated cohort. The IgG titres decayed faster after vaccination with Sinopharm than following the Pfizer-BioNTech vaccine.

Keywords: IgG, waning immunity, Pfizer, Sinopharm, N protein

DOI: 10.3233/HAB-230004

Journal: Human Antibodies, vol. 31, no. 1-2, pp. 19-25, 2023