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Immunogenicity of a third dose viral-vectored COVID-19 vaccine after receiving two-dose inactivated vaccines in healthy adults

2021; Elsevier BV; Volume: 40; Issue: 3 Linguagem: Inglês

10.1016/j.vaccine.2021.11.083

1873-2518

Ritthideach Yorsaeng, Nungruthai Suntronwong, Harit Phowatthanasathian, Suvichada Assawakosri, Sitthichai Kanokudom, Thanunrat Thongmee, Preeyaporn Vichaiwattana, Chompoonut Auphimai, Lakkhana Wongsrisang, Donchida Srimuan, Thaksaporn Thatsanatorn, Sirapa Klinfueng, Natthinee Sudhinaraset, Nasamon Wanlapakorn, Yong Poovorawan,

Vaccine Coverage and Hesitancy

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.