Thanh T.T.Tu N.T.K.Nguyet L.A.Thuy C.T.Thuan N.L.T.Ny N.T.H.Nhu L.N.T.Thanh L.K.Hong N.T.T.Anh N.T.Truong N.T.Chau N.V.V.Yen L.M.Van E P.Thuong N.P.Van Truc N.Trung P.H.Yap W.C.Pandey R.Yee S.Weng R.Mongkolsapaya J.Dejnirattisai W.Hamers R.L.Chantratita N.Screaton G.Dunachie S.J.Jones E.Y.Stuart D.I.Dung N.T.Thwaites G.Wang L.F.Tan C.W.Tan L.V.Mahidol University2024-08-312024-08-312024-10-01International Journal of Infectious Diseases Vol.147 (2024)12019712https://repository.li.mahidol.ac.th/handle/123456789/100666Objectives: We studied the immunogenicity after primary and booster vaccinations of the Abdala COVID-19 vaccine, a receptor-binding domain protein subunit vaccine, in Vietnamese people by determining the level of neutralization and cross-neutralization activities against the ancestral SARS-CoV-2 and its variants and SARS-CoV-1. Methods: We performed a prospective observational study, enrolling adults aged 19-59 years in Dong Thap province, southern Vietnam, and collected blood samples from baseline until 4 weeks after the booster dose. We measured anti-nucleocapsid, anti-spike, and neutralizing antibodies against SARS-CoV-2 and assessed the cross-neutralization against 14 SARS-CoV-2 variants and SARS-CoV-1. Complementary antibody data came from Vietnamese health care workers fully vaccinated with ChAdOx1-S. Results: After primary vaccination, anti-spike antibody and neutralizing antibodies were detectable in 98.4% and 87% of 251 study participants, respectively, with neutralizing antibody titers similar to that induced by ChAdOx1-S vaccine. Antibody responses after a homologous (Abdala COVID-19) or heterologous (messenger RNA BNT162b2) booster could neutralize 14 SARS-CoV-2 variants (including Omicron) and SARS-CoV-1. Conclusions: Abdala COVID-19 vaccine is immunogenic in Vietnamese people. Enhanced antibody response after a booster dose could cross-neutralize 14 SARS-CoV-2 variants and SARS-CoV-1. Our results have added to the growing body of knowledge about the contribution of protein subunit vaccine platforms to pandemic control.MedicineArticleSCOPUS10.1016/j.ijid.2024.1071732-s2.0-852017844281878351139094762