Immunogenicity of Oxford-AstraZeneca COVID-19 Vaccine in Vietnamese Health-Care Workers

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  • 1 Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam;
  • | 2 Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam;
  • | 3 Institute of Pasteur, Nha Trang City, Vietnam;
  • | 4 Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom

We studied the immunogenicity of the Oxford-AstraZeneca vaccine in health-care workers of a major infectious diseases hospital in Vietnam. We measured neutralizing antibodies before and 14 days after each dose, and at day 28 and month 3 after dose 1. A total of 554 workers (136 men and 418 women; age range, 22–71 years; median age, 36 years) participated with the study. Of the 144 participants selected for follow-up after dose 1, 104 and 94 gave blood for antibody measurement at weeks 6 and 8, and at month 3 after dose 1, respectively. The window time between the two doses was 6 weeks. At baseline, none had detectable neutralizing antibodies. After dose 1, the proportion of participants with detectable neutralizing antibodies increased from 27.3% (151 of 554) at day 14 to 78.0% (432 of 554) at day 28. Age correlated negatively with the development and the levels of neutralizing antibodies. However, at day 28, these differences were less profound, and women had a greater seroconversion rate and greater levels of neutralizing antibodies than men. After dose 2, these age and gender associations were not observable. In addition, the proportion of study participants with detectable neutralizing antibodies increased from 70.2% (73 of 104) before dose 2 (week 6, after dose 1) to 98.1% (102 of 104) 14 days later. At month 3, neutralizing antibodies decreased and 94.7% (89 of 94) of the study participants remained seropositive. The Oxford-AstraZeneca COVID-19 vaccine is immunogenic in Vietnamese health-care workers. These data are critical to informing the deployment of the COVID-19 vaccine in Vietnam and in Southeast Asia, where vaccination coverage remains inadequate.

Author Notes

Address correspondence to Nguyen Van Vinh Chau or Le Van Tan, 764 Vo Van Kiet, District 5, Ho Chi Minh City, Vietnam. E-mails: chaunvv@oucru.org and tanlv@oucru.org

Financial support: This study was funded by the Wellcome Trust of Great Britain (106680/B/14/Z and 204904/Z/16/Z) and the National Institutes of Health/National Institute of Allergy and Infectious Diseases (HHSN272201400007C, subcontract no. S000596-JHU).

Authors’ addresses: Nguyen Van Vinh Chau, Nguyen Thanh Truong, Le Mau Toan, Nguyen Thanh Dung, Le Manh Hung, Mai Thanh Nhan, Dinh Nguyen Huy Man, Nghiem My Ngoc, Huynh Phuong Thao, and Tran Nguyen Hoang Tu, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam, E-mails: chaunvv@oucru.org, bsthanhtruong@gmail.com, drmautoan@gmail.com, bsdungbvbnd@gmail.com, bslemanhhung@gmail.com, mainhanyds@gmail.com, bshuyman@gmail.com, ngocnm@oucru.org, hpt251984@yahoo.com.vn, and bs.hoangtu.bvbnd@gmail.com. Lam Anh Nguyet, Nguyen Thi Han Ny, Le Kim Thanh, Nguyen To Anh, Nguyen Thi Thu Hong, Le Nguyen Truc Nhu, Lam Minh Yen, Tran Tan Thanh, and Le Van Tan, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam, E-mails: nguyetla@oucru.org, nynth@oucru.org, thanhlk@oucru.org, anhnt@oucru.org, hongntt@oucru.org, nhulnt@oucru.org, yenlm@oucru.org, thanhtt@oucru.org, and tanlv@oucru.org. Huynh Kim Mai and Do Thai Hung, Institute of Pasteur, Nha Trang City, Vietnam, E-mails: mai064@yahoo.com and hungdt02@yahoo.com. Marc Choisy, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam, and Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK, E-mail: mchoisy@oucru.org. Guy Thwaites, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam, and Institute of Pasteur, Nha Trang City, Vietnam, E-mail: gthwaites@oucru.org.

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