Kinetics of Neutralizing Antibodies against Omicron Variant in Vietnamese Healthcare Workers after Primary Immunization with ChAdOx1-S and Booster Immunization with BNT162b2
Van Vinh Chau N., Nguyet LA., Dung NT., Quang VM., Truong NT., Toan LM., Hung LM., Man DNH., Khoa DB., Phong NT., Ngoc NM., Thao HP., Ty DTB., Thanh PB., Ny NTH., Thanh LK., Thuy CT., Anh NT., Hong NTT., Nhu LNT., Yen LM., Thwaites G., Thanh TT., Van Tan L., Chambers M., Choisy M., Day J., Dong HKT., Dong THT., Du HD., Dung VTV., Fisher J., Flower B., Geskus R., Hang VTK., Ho QC., Ho TBH., Ho VH., Hung VB., Huong DT., Huynh LAH., Huynh NH., Huynh TT., Huynh XY., Kestelyn E., Kesteman T., Lawson K., Jones L., Le KT., Van Khoa Le D., Le THN., Lewycka SO., Lam MY., Le THL., Nam VN., Ngo TH., Nguyen BT., Nguyen DM., Nguyen HY., Nguyen LTM., Nguyen MN., Nguyen TH., Nguyen THQ., Nguyen TN., Nguyen TTN., Nguyen THN., Nguyen THT., Nguyen THY., Nguyen THT., Nguyen TKN., Nguyen TKT., Nguyen TND., Nguyen TPD., Nguyen TT., Nguyen TTH., Nguyen TT., Nguyen TTT., Nguyen XT., Nhung DP., Van Ninh TT., Ong PT., Pham NT., Phan NQK., Phung HTK., Phung KL., Phung LKY., Phung THN., Rahman M., Thuong NTH., Tran BH., Tran DTH., Van Anh Tran K., Tran MH., Tran TBN., Tran TH., Tran TH., Trinh ST., van Doorn HR., Van Nuil J., Vidaillac CP.
We studied the development and persistence of neutralizing antibodies against SARS-CoV-2 ancestral strain, and Delta and Omicron (BA.1 and BA.2) variants in Vietnamese healthcare workers (HCWs) up to 15 weeks after booster vaccination. We included 47 HCWs, including group 1 (G1, N 521) and group 2 (G2; N 526) without and with breakthrough Delta variant infection before booster immunization, respectively). The study participants had completed primary immunization with ChAdOx1-S and booster vaccination with BNT162b2. Neutralizing antibodies were measured using a surrogate virus neutralization assay. Of the 21 study participants in G1, neutralizing antibodies against ancestral strain, Delta variant, BA.1, and BA.2 were (almost) abolished at month 8 after the second dose, but all had detectable neutralizing antibodies to the study viruses at week 2 post booster dose. Of the 26 study participants in G2, neutralizing antibody levels to BA.1 and BA.2 were significantly higher than those to the corresponding viruses measured at week 2 post breakthrough infection and before the booster dose. At week 15 post booster vaccination, neutralizing antibodies to BA.1 and BA.2 dropped significantly, with more profound changes observed in those without breakthrough Delta variant infection. Booster vaccination enhanced neutralizing activities against ancestral strain and Delta variant compared with those induced by primary vaccination. These responses were maintained at high levels for at least 15 weeks. Our findings emphasize the importance of the first booster dose in producing cross-neutralizing antibodies against Omicron variant. A second booster to maintain long-term vaccine effectiveness against the currently circulating variants merits further research.