Abstract
In June 2021, Thailand was hit by the delta variant of SARS-CoV-2 resulting in the biggest wave of COVID-19. Due to the widespread delta variant, more than 600 healthcare workers had COVID-19 despite completion of two-dose CoronaVac. The Ministry of Public Health recommended that healthcare workers received a third dose of AZD1222 to increase level of protection against SARS-CoV-2. However, immune response after the AZD1222 booster in individuals who completed the two-dose CoronaVac vaccine are limited. In this study, sera from those who received a booster of AZD1222 in June-July 2021 were tested for SARS-CoV-2 spike receptor-binding-domain (RBD) IgG, anti-RBD total immunoglobulins and anti-spike protein 1 (S1) IgA. The neutralizing activities in a subset of serum samples were tested against the wild type and variants of concern (B.1.1.7, B.1.617.2, and B.1.351) using an enzyme-linked immunosorbent assay-based surrogate virus neutralization test. Participants who received the booster of AZD1222 possessed higher levels of spike RBD-specific IgG, total immunoglobulins, and anti-S1 IgA than the two-dose vaccinees (p < 0.001). They also elicited higher neutralizing activity against the wild type and all variants of concern than the recipients of the two-dose vaccines. This study demonstrated a high immunogenicity of the AZD1222 booster in individuals who completed the two-dose inactivated vaccines.
Keywords: Booster dose; COVID-19; Immunogenicity; Inactivated vaccine; Virus vector.
【저자키워드】 COVID-19, immunogenicity, Inactivated vaccine, booster dose, Virus vector, 【초록키워드】 public health, SARS-CoV-2, IgG, Vaccine, immune response, immunogenicity, Healthcare workers, Inactivated Vaccines, Vaccines, B.1.351, immunoglobulins, variant, CoronaVac, variants of concern, B.1.617.2, delta variant, variants, healthcare worker, Protein, Neutralizing activity, AZD1222, Immunoglobulin, Inactivated vaccine, B.1.1.7, RBD, IgA, sera, virus neutralization test, neutralization test, booster dose, wild type, booster, surrogate virus neutralization test, Anti-spike, SARS-CoV-2 spike, dose, anti-RBD, serum samples, recipients, enzyme, individual, completion, participant, neutralizing activities, recipient, serum sample, RBD-specific IgG, Public, widespread, enzyme-linked immunosorbent, Virus vector, vaccinee, variant of SARS-CoV-2, resulting, tested, demonstrated, elicited, subset, 【제목키워드】 COVID-19 vaccine, dose, healthy, receiving,