Assessing COVID-19 IgG levels among vaccinated and non-vaccinated individuals in Mthatha - South africa: A case-control approach.

Faced with the emergence of new COVID-19 variants, vaccine hesitancy remains a major challenge in the global fight against the pandemic, particularly in rural areas. Understanding the immune response to vaccination is crucial for dispelling doubts and building public trust. By providing tangible evidence of vaccine effectiveness, this approach could not only alleviate skepticism but also contribute to preventing future epidemics. To evaluate and compare salivary SARS-CoV-2 IgG antibody levels between vaccinated and unvaccinated individuals in Mthatha, South Africa. A case-control study involved 183 participants aged 18 years and above, comprising 91 vaccinated and 92 unvaccinated individuals in Mthatha, South Africa. Saliva samples were collected and analyzed using Bio-Plex Pro Human IgG SARS-CoV-2 Assay to detect SARS-CoV-2 IgG antibodies. Data were processed using STATA/SE version 18.0. The results of this study demonstrate that participants vaccinated against COVID-19 exhibit significantly (p = 0.01) higher salivary IgG antibody levels (988 ± 104 pg/mL) compared to unvaccinated individuals (552 ± 83 pg/mL). No significant difference was observed between those vaccinated recently (975 ± 175 pg/mL) and those vaccinated more than two years ago (990 ± 215 pg/mL). Additionally, participants who received two doses showed notably higher antibody levels (1790 ± 445 pg/mL) compared to those who received a single dose (668 ± 75 pg/mL), with a significant difference (p = 0.004). In summary, vaccination is associated with higher salivary anti-SARS-CoV-2 IgG levels, influenced by vaccine type and number of doses. The detection of IgG in unvaccinated individuals and the lack of a defined protective correlate underscore the need for further studies on both humoral and cellular immunity to clarify the durability and magnitude of the immune response. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-025-00942-w.