Durability of COVID-19 Vaccine-Induced Antibody Responses: BNT162b2 Versus CoronaVac at One Year

Abstract

Background: Understanding the long-term persistence of antibody responses induced by different coronavirus disease-19 (COVID-19) vaccine platforms is crucial for shaping future vaccination strategies. Objectives: This study evaluated neutralizing antibody responses in individuals with a documented negative history of COVID-19 during the six months. Methods: This prospective observational cohort study assessed the persistence of humoral immune responses in 100 adult participants (mean age = 34.9 ± 12.8 years; 62% female) who received either the messenger RNA (mRNA)-based BNT162b2 (n = 51) or the inactivated CoronaVac (n = 49) vaccine. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) levels were measured at three time points: December 2022, June 2023, and December 2023. The temporal changes in antibody levels and seropositivity were evaluated, and group comparisons were made using appropriate statistical analyses. Results: Although SARS-CoV-2 IgG levels significantly declined over time in both vaccine groups, all participants remained seropositive throughout the follow-up period. Individuals vaccinated with BNT162b2 exhibited significantly higher IgG levels at all time points compared to those who received CoronaVac (P < 0.001). The cumulative decrease in IgG levels was 43.0% in the BNT162b2 group and 64.5% in the CoronaVac group. No significant association was found between antibody kinetics and participants’ age or sex. Conclusions: The BNT162b2 vaccine elicited a stronger and more durable humoral immune response than the CoronaVac vaccine. The sustained seropositivity, despite declining antibody levels, may reflect the effect of hybrid immunity, potentially enhanced by exposure to circulating Omicron and other possible subvariants of SARS-CoV-2. These findings emphasize the importance of evaluating both magnitude and persistence of vaccine-induced immunity when shaping booster strategies and selecting vaccination platforms.