Dynamics of Different Classes and Subclasses of Antibody Responses to Severe Acute Respiratory Syndrome Coronavirus 2 Variants after Coronavirus Disease 2019 and CoronaVac Vaccination in Thailand

Abstract

The antibody responses to new SARS-CoV-2 variants that occur in different populations remain unclear. In this study, we recruited 60 participants, including COVID-19 patients and CoronaVac-vaccinated individuals, in Thailand and determined the dynamic levels of the IgG, IgA, IgM, and IgG subclasses of antibodies against the spike protein (S) of four SARS-CoV-2 strains.

Comparison of Kinetics of Antibody Avidity and IgG Subclasses’ Response in Patients with COVID-19 and Healthy Individuals Vaccinated with the BNT162B2 (Comirnaty, Pfizer/BioNTech) mRNA Vaccine

“…Seven months after the two doses of the vaccine, there was a decrease in IgG1 and a very clear increase in IgG4 antibodies. Irrgang et al [6] and Poolchanuan et al [5] also observed a significant increase in IgG4 levels after vaccination with the second dose of the mRNA vaccine, but not after vaccination with adenoviral vectors or an inactivated vaccine. IgG4 levels were further boosted by the third dose of the mRNA vaccine.…”

“…Investigation of the avidity of IgG antibodies as well as specific antibodies in individual IgG subclasses offers a better insight into the kinetics of the humoral response over the course of the COVID-19 infection, allowing us to assess the effectiveness of preventive vaccinations [4][5][6].…”

Non-neutralizing functions in anti-SARS-CoV-2 IgG antibodies

“…With respect to adenovector vaccines, only a fraction of individuals receiving the AstraZeneca vaccine (AZD1222, ChadOx1) reached anti-S antibody levels above 10 μg/ml [ 60 ]⁠, while the Johnson & Johnson vaccine (Ad26Cov2-S) had only a concentration of 1 μg/ml, similar to mild and moderate infection [ 61 ]⁠. Inactivated vaccines typically elicit antibody responses that are comparable or sometimes weaker in comparison to those observed in individuals who have recovered from COVID-19 [ 75 , 76 ]⁠. Inactivated and adenovector-based vaccines, which have the lowest efficacy among all vaccines, are likely to rely mostly on other mechanisms, like T-cell-mediated immunity, for protection.…”