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Original Research
Kinetics of anti-SARS-CoV-2 IgG in saliva and serum post infection, and subsequent vaccination in South Africa
Submitted: 08 October 2025 | Published: 26 June 2026
About the author(s)
Maemu P. Gededzha, Department of Virology, School of Medicine, Sefako Makgatho Health Sciences University, Pretoria, South AfricaMixo Sibiya, Department of Immunology, National Health Laboratory Service, Johannesburg, South Africa
Celine Pellaton, Service of Immunology and Allergy Unit, University of Lausanne, Lausanne University Hospital, Lausanne, Switzerland
Kubashni Woeber, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Duduzile Nsibande, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Nobuhle Mchunu, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa; and, Biostatistics Research Unit, South African Medical Research Council, Durban, South Africa
Brodie Daniels, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Terusha Chetty, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Reshmi Dassaye, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Khanya Mohlabi, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa
Shameem Jaumdally, Centre for Lung Infection and Immunity, Division of Pulmonology, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; and, South African MRC Centre for the Study of Antimicrobial Resistance, University of Cape Town, Cape Town, South Africa
Keertan Dheda, Centre for Lung Infection and Immunity, Division of Pulmonology, Department of Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; and, South African MRC Centre for the Study of Antimicrobial Resistance, University of Cape Town, Cape Town, South Africa; and, Faculty of Infectious and Tropical Diseases, Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, South Africa
Ruth Lekalakala, Department of Pathology, Faculty of Health Sciences, University of Limpopo, Polokwane, South Africa; and, Medical Microbiology, Polokwane Laboratory, National Health Laboratory Service, Polokwane, South Africa
Shabir A. Madhi, South African Medical Research Council: Wits Vaccines and Infectious Diseases Analytics Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; and, Wits Infectious Diseases and Oncology Research Institute, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
Elizabeth Mayne, Division of Immunology, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; and, National Health Laboratory Service, Groote Schuur Hospital, Cape Town, South Africa
Glenda Gray, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa; and, Wits Infectious Diseases and Oncology Research Institute, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
Yves Levy, The Vaccine Research Institute, Faculty of Médicine, Université Paris-Est Créteil, Créteil, France
Craig Fenwick, Department of Immunology, Henri-Mondor Albert-Chenevier Hospital, Créteil, France
Song Ding, EuroVacc Foundation, Lausanne, Switzerland
Penny L. Moore, SAMRC Antibody Immunity Research Unit, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; and, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa; and, Centre for the AIDS Programme of Research in South Africa, Durban, South Africa
Ameena Goga, HIV and Other Infectious Diseases Research Unit, South African Medical Research Council, Cape Town, South Africa; and, Department of Paediatrics and Child Health, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
Abstract
Background: Understanding mucosal immune response to Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination, and its correlation to systemic responses could improve vaccine development. There is limited data on mucosal and systemic antibody responses to SARS-CoV-2 infection and vaccination in African populations.
Objective: This study assessed serum and saliva antibody ratios in a cohort of SARS-CoV-2 infected and vaccinated participants followed up for 12 months.
Methods: This longitudinal study comprised of 67 SARS-CoV-2, PCR-confirmed participants who were recruited as part of a COVID-19 Point of Care Study, between January 2021 and September 2022. For this analysis, 254 serum and 214 saliva samples (205 of which were matched), were collected at baseline, 6, 9, and 12 months. Antibodies against Spike (S) and nucleocapsid (N) SARS-CoV-2 were assessed by in-house Luminex assay.
Results: Serum and saliva anti-S IgG from were detected for up to 12 months in majority of participants (93.5% and 90%), regardless of vaccination status. There was a concordance between paired serum and saliva antibody in 80.5% anti-S IgG and 41.7% anti-N IgG of samples. There was a weak but significant correlation between the matched serum and saliva samples (ρ = 0.42, p < 0.001 for anti-S and ρ = 0.33, p < 0.001 for anti-N). Longitudinal analysis in participants who were vaccinated with either the Ad26.COV2 or BNT162b2 COVID-19 vaccine after their baseline visit, serum anti-S IgG significantly increased (p = 0.023 and p = 0.038), compared with unvaccinated participants. Breakthrough infections or reinfections were identified in (35/62) 56.5% of vaccinated and unvaccinated participants.
Conclusion: This study reports the correlation of the anti-S and anti-N IgG responses in serum and saliva following SARS-CoV-2 infection and subsequent vaccination in low-middle income setting. Furthermore, high breakthroughs and reinfection were reported.
What this study adds: The study findings are consistent with those from high-income settings, supporting correlation between systemic and mucosal immunity and booster vaccination as a long-term strategy to control SARS-CoV-2.
Keywords
Sustainable Development Goal
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