# Immunoglobulin G and neutralizing antibody response after CoronaVac

## TL;DR

This study examines how the CoronaVac vaccine affects antibody levels in healthcare workers, finding that while IgG peaks early, neutralizing antibodies to variants remain low over time.

## Contribution

The study provides new insights into the durability of neutralizing antibody responses to SARS-CoV-2 variants after CoronaVac vaccination.

## Key findings

- IgG seroconversion peaked at 68.2% at D30 and stabilized afterward.
- Neutralizing antibodies to variants B.1.351 and P.1 remained consistently lower than to Wuhan and B.1.1.7.
- Neutralizing antibody detection in IgG-positive individuals dropped from 92.3% at D48 to 42.8% at D90.

## Abstract

The aim of this study was to evaluate the kinetics of immunoglobulin G and neutralizing antibody responses following vaccination with CoronaVac in healthcare professionals.

A cohort of 35 healthcare professionals was recruited, and blood samples were collected to assess immunoglobulin G detection and neutralizing antibodies against severe acute respiratory syndrome coronavirus 2.

Immunoglobulin G seroconversion peaked at D30 (68.2%, 15/22), followed by stabilization at D48 and D90. Logistic regression confirmed a significant association between time post-vaccination and seroconversion (p=0.0043). Neutralizing antibody analysis showed a stable detection rate for Nab V1 (Wuhan and B.1.1.7) between D48 and D90 (p>0.9999), while Nab V2 (B.1.351 and P.1) remained consistently lower. Among immunoglobulin G-positive individuals, 92.3% (12/13) had neutralizing antibodies at D48, decreasing to 42.8% (6/14) at D90.

CoronaVac effectively induces immunoglobulin G seroconversion, peaking at D30. However, neutralizing responses to emerging variants were lower, suggesting the need for booster doses to maintain immunity. These findings highlight the importance of monitoring vaccine-induced immunity over time.