Evaluation of Humoral Immunity Induced by Commonly Administered COVID-19 Vaccines in Middle-aged Iranians

Abstract

Background: Using a comparative analysis and assessment approach on a number of vaccine under investigation in a specific group is pertinent to local health policy and to our scientific understanding of vaccine responses. Objectives: In this double-blind, cross-sectional study, the efficacy of two platforms inactivated COVID-19 vaccines (CO-Iran Barekat and Sinopharm) and adenoviral-vector COVID-19 vaccines (AstraZeneca and Sputnik V) most commonly used in the Iranian population was evaluated. The target population was 40 - 60 years old. Humoral immune response evaluated by the production of virus-neutralizing antibodies and immunoglobulin G binding to the receptor-binding domain (RBD). Methods: Four hundred twenty volunteers aged 40 - 60 years were vaccinated with the COVID-19 vaccines including CO-Iran Barekat, Sinopharm, AstraZeneca and Sputnik. After receiving the second dose, the humoral immune response was assessed using a conventional neutralizing antibody assay and IgG ELISA. Results: Recipients of the Barekat and Sinopharm vaccines had negative IgG responses of ~15.3% and ~32.97% respectively, while a negative IgG response in the Sputnik V vaccine group showed 10.58%. No negative IgG response was noted with the AstraZeneca group. In the neutralizing antibody assay against SARS-CoV-2, AstraZeneca, Sputnik V, COV-Iran Barekat and Sinopharm showed effective protection in 87.73%, 59.61%, 54.23% and 35.16% respectively. The S1-IgG and SARS-CoV-2 neutralization responses found with Sinopharm and COV-Iran Barekat were similar to those seen vaccinated individuals. In contrast, the conventional live-virus neutralization titer (cVNT50) in SARS-CoV-2-AstraZeneca vaccines was much higher than any of the other three groups. Also data analysis of adverse vaccine event revealed that injection site pain is the most common adverse event in the four groups. Conclusions: The highest levels of neutralizing antibodies were found with AstraZeneca that further support its higher effective potential for protection to SARS-CoV-2. Antibody levels were measured with ELISA IgG Kits and a conventional neutralizing antibody assay technique.