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1Institute of Vaccines and Medical Biologicals (IVAC), Nha Trang, Vietnam
2Tay Nguyen Institute of Hygiene and Epidemiology, Buon Me Thuot, Vietnam
3Khanh Hoa Medical Service, Nha Trang, Vietnam
4Ninh Hoa District Medical Center, Khanh Hoa, Vietnam
5National Institute of Hygiene and Epidemiology, Hanoi, Vietnam
6School of Preventive Medicine and Public Health, Hanoi Medical University, Hanoi, Vietnam
© 2021, Korean Society of Epidemiology
This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
CONFLICT OF INTEREST
The authors have no conflicts of interest to declare for this study.
FUNDING
This research received support from the People’s Committee of Khanh Hoa Province.
AUTHOR CONTRIBUTIONS
Conceptualization: CVC, BLV. Data curation: VPQ. Formal analysis: CVC, TPQ, LHT, DNV. Funding acquisition: BLV. Methodology: CVC, BLV, TPQ. Project administration: VPQ, LHT. Visualization: DNV, PQT. Writing – original draft: CVC, DNV, TPQ, BLV. Writing – review & editing: CVC, VPQ, LHT, DNV, TPQ, BLV.
Time | Persistence of at least a 1/10 amount of antibodies, n (%) | Seroconversion (≥4 times higher than baseline), n (%) | Geometric mean titer1 | Geometric mean titer ratio1 |
---|---|---|---|---|
Baseline2 | 11 (12.8) | - | 5.6 | 1.0 |
21 d after full vaccination (42 d after the first dose) | 86 (100) | 81 (92.4) | 66.8 | 11.8 |
30 mo3 | 73 (84.9) | 49 (57.0) | 22.3 | 4.0 |
36 mo3 | 45 (52.3) | 26 (30.2) | 12.0 | 2.1 |
Characteristics | Total | 30 mo | 36 mo | ||||
---|---|---|---|---|---|---|---|
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|
|
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n (%) | n (%) | OR (95% CI)1 | p-value | n (%) | OR (95% CI)1 | p-value | |
Demographics | |||||||
Sex | |||||||
Male | 23 (26.7) | 17 (73.9) | 0.35 (0.09, 1.40) | 0.09 | 10 (43.5) | 0.62 (0.21, 1.78) | 0.32 |
Female | 63 (73.3) | 56 (88.9) | 1.00 (reference) | 35 (55.6) | 1.00 (reference) | ||
Age (yr) | |||||||
18–40 | 39 (45.3) | 37 (94.9) | 5.65 (1.06, 39.87) | 0.02 | 24 (61.5) | 1.98 (0.77, 5.17) | 0.12 |
41–65 | 47 (54.7) | 36 (76.6) | 1.00 (reference) | 21 (44.7) | 1.00 (reference) | ||
|
|||||||
Personal behaviors | |||||||
Alcohol use | |||||||
Yes | 17 (19.8) | 14 (82.4) | 0.79 (0.17, 4.19) | 0.74 | 10 (58.8) | 1.39 (0.42, 4.64) | 0.55 |
No | 69 (80.2) | 59 (85.5) | 1.00 (reference) | 35 (50.7) | 1.00 (reference) | ||
Smoking | |||||||
Yes | 14 (16.3) | 11 (78.6) | 0.59 (0.12, 3.22) | 0.75 | 6 (42.9) | 0.63 (0.17, 2.29) | 0.44 |
No | 72 (83.7) | 62 (86.1) | 1.00 (reference) | 39 (54.2) | 1.00 (reference) | ||
|
|||||||
Medical history | |||||||
Having flu-like symptoms in the past 18 mo or between 2 visits | |||||||
Yes | 33 (38.4) | 29 (87.9) | 1.19 (0.32, 4.59) | 0.78 | 1 (11.1) | 0.09 (0.01, 0.81) | 0.02 |
No | 53 (61.6) | 44 (83.0) | 1.00 (reference) | 44 (57.1) | 1.00 (reference) | ||
Having other diseases in the past 18 mo or between 2 visits | |||||||
Yes | 7 (8.1) | 7 (100) | - | 0.53 | 0 (0.0) | - | 0.43 |
No | 79 (91.9) | 66 (83.5) | - | 45 (53.6) | - | ||
|
|||||||
Exposure risk factors | |||||||
Having a poultry farm | |||||||
Yes | 53 (61.6) | 44 (83.0) | 0.70 (0.16, 2.72) | 0.76 | 30 (56.6) | 1.57 (0.60, 4.12) | 0.31 |
No | 33 (38.4) | 29 (87.9) | 1.00 (reference) | 15 (45.5) | 1.00 (reference) | ||
Coming into direct contact with poultry | |||||||
Yes | 49 (57.0) | 41 (83.7) | 0.80 (0.20, 3.06) | 0.72 | 28 (57.1) | 1.57 (0.61, 4.06) | 0.30 |
No | 37 (43.0) | 32 (86.5) | 1.00 (reference) | 17 (45.9) | 1.00 (reference) | ||
Directly slaughtering and processing poultry | |||||||
Yes | 5 (5.8) | 5 (100) | - | 0.33 | 1 (20.0) | 0.21 (0.01, 2.15) | 0.30 |
No | 81 (94.2) | 68 (84.0) | - | 44 (54.3) | 1.00 (reference) |
Time | Persistence of at least a 1/10 amount of antibodies, n (%) | Seroconversion (≥4 times higher than baseline), n (%) | Geometric mean titer |
Geometric mean titer ratio |
---|---|---|---|---|
Baseline |
11 (12.8) | - | 5.6 | 1.0 |
21 d after full vaccination (42 d after the first dose) | 86 (100) | 81 (92.4) | 66.8 | 11.8 |
30 mo |
73 (84.9) | 49 (57.0) | 22.3 | 4.0 |
36 mo |
45 (52.3) | 26 (30.2) | 12.0 | 2.1 |
Characteristics | Total | 30 mo | 36 mo | ||||
---|---|---|---|---|---|---|---|
|
|
| |||||
n (%) | n (%) | OR (95% CI) |
p-value | n (%) | OR (95% CI) |
p-value | |
Demographics | |||||||
Sex | |||||||
Male | 23 (26.7) | 17 (73.9) | 0.35 (0.09, 1.40) | 0.09 | 10 (43.5) | 0.62 (0.21, 1.78) | 0.32 |
Female | 63 (73.3) | 56 (88.9) | 1.00 (reference) | 35 (55.6) | 1.00 (reference) | ||
Age (yr) | |||||||
18–40 | 39 (45.3) | 37 (94.9) | 5.65 (1.06, 39.87) | 0.02 | 24 (61.5) | 1.98 (0.77, 5.17) | 0.12 |
41–65 | 47 (54.7) | 36 (76.6) | 1.00 (reference) | 21 (44.7) | 1.00 (reference) | ||
| |||||||
Personal behaviors | |||||||
Alcohol use | |||||||
Yes | 17 (19.8) | 14 (82.4) | 0.79 (0.17, 4.19) | 0.74 | 10 (58.8) | 1.39 (0.42, 4.64) | 0.55 |
No | 69 (80.2) | 59 (85.5) | 1.00 (reference) | 35 (50.7) | 1.00 (reference) | ||
Smoking | |||||||
Yes | 14 (16.3) | 11 (78.6) | 0.59 (0.12, 3.22) | 0.75 | 6 (42.9) | 0.63 (0.17, 2.29) | 0.44 |
No | 72 (83.7) | 62 (86.1) | 1.00 (reference) | 39 (54.2) | 1.00 (reference) | ||
| |||||||
Medical history | |||||||
Having flu-like symptoms in the past 18 mo or between 2 visits | |||||||
Yes | 33 (38.4) | 29 (87.9) | 1.19 (0.32, 4.59) | 0.78 | 1 (11.1) | 0.09 (0.01, 0.81) | 0.02 |
No | 53 (61.6) | 44 (83.0) | 1.00 (reference) | 44 (57.1) | 1.00 (reference) | ||
Having other diseases in the past 18 mo or between 2 visits | |||||||
Yes | 7 (8.1) | 7 (100) | - | 0.53 | 0 (0.0) | - | 0.43 |
No | 79 (91.9) | 66 (83.5) | - | 45 (53.6) | - | ||
| |||||||
Exposure risk factors | |||||||
Having a poultry farm | |||||||
Yes | 53 (61.6) | 44 (83.0) | 0.70 (0.16, 2.72) | 0.76 | 30 (56.6) | 1.57 (0.60, 4.12) | 0.31 |
No | 33 (38.4) | 29 (87.9) | 1.00 (reference) | 15 (45.5) | 1.00 (reference) | ||
Coming into direct contact with poultry | |||||||
Yes | 49 (57.0) | 41 (83.7) | 0.80 (0.20, 3.06) | 0.72 | 28 (57.1) | 1.57 (0.61, 4.06) | 0.30 |
No | 37 (43.0) | 32 (86.5) | 1.00 (reference) | 17 (45.9) | 1.00 (reference) | ||
Directly slaughtering and processing poultry | |||||||
Yes | 5 (5.8) | 5 (100) | - | 0.33 | 1 (20.0) | 0.21 (0.01, 2.15) | 0.30 |
No | 81 (94.2) | 68 (84.0) | - | 44 (54.3) | 1.00 (reference) |
Immunological indicators. Before receiving the IVACFLU-A/H5N1 vaccine. At 30 months and 36 months after receiving both IVACFLU-A/H5N1 vaccines – full vaccination.
OR, odds ratio; CI, confidence interval. Univariate logistic regression models.