Table 1 Individual characteristics of participants

Total

2071

36.2

3656

63.8

5727

100.0

Age group

 16–20 years old

809

39.2

1491

40.9

2300

40.3

< 0.001

 21–25 years old

955

46.3

1411

38.7

2366

41.5

 More than years old

299

14.5

741

20.3

1040

18.2

Gender

 Male

676

32.9

1075

29.6

1751

30.8

0.01

 Female

1381

67.1

2556

70.4

3937

69.2

Marital status

 Singled/Divorced/Widowed

1833

89.4

3024

83.6

4857

85.7

< 0.001

 Married

218

10.6

595

16.4

813

14.3

Living location

 Rural areas

1408

68.1

2229

61.1

3637

63.7

< 0.001

 Town

254

12.3

519

14.2

773

13.5

 Urban/Mountainous/Island

406

19.6

898

24.6

1304

22.8

Occupation

 Student

1688

81.7

2810

77.1

4498

78.8

< 0.001

 Nurse, technician

147

7.1

344

9.4

491

8.6

 Doctor

194

9.4

380

10.4

574

10.1

 Other

36

1.7

110

3.0

146

2.6

Mean income/month

 Under 5 million VND

1693

84.8

2865

80.6

4558

82.1

< 0.001

 5–10 million VND

221

11.1

522

14.7

743

13.4

 10 million VND or above

82

4.1

167

4.7

249

4.5

Monthly household income per capita

 Under 5 million VND

1076

52.7

1674

46.3

2750

48.6

< 0.001

 5–10 million VND

601

29.5

1255

34.7

1856

32.8

 10 million VND or above

363

17.8

685

19.0

1048

18.5

Type of workplace

 Student

1398

67.7

2321

63.7

3719

65.2

< 0.001

 University hospital

354

17.2

608

16.7

962

16.9

 General hospital

175

8.5

446

12.2

621

10.9

 CDC/Medical center/Public health station

86

4.2

178

4.9

264

4.6

 Other

51

2.5

88

2.4

139

2.4

Levels of health facilities

 National Hospital

155

7.5

346

9.5

501

8.8

0.04

 Provincial/city hospital

715

34.8

1216

33.5

1931

33.9

 University hospital

1116

54.3

1977

54.4

3093

54.4

 Other

68

3.3

96

2.6

164

2.9

Working experience

 Students

1424

69.1

2379

65.3

3803

66.6

< 0.001

 < 1 years

108

5.2

136

3.7

244

4.3

 1–5 years

320

15.5

542

14.9

862

15.1

 More than 5 years

210

10.2

587

16.1

797

14.0

Having part-time job

298

14.5

468

13.0

766

13.5

0.10

Work retention

Total

2071

36.2

3656

63.8

5727

100.0

Age group

 16–20 years old

809

39.2

1491

40.9

2300

40.3

< 0.001

 21–25 years old

955

46.3

1411

38.7

2366

41.5

 More than 25 years old

299

14.5

741

20.3

1040

18.2

Gender

 Male

676

32.9

1075

29.6

1751

30.8

0.01

 Female

1381

67.1

2556

70.4

3937

69.2

Marital status

 Singled/Divorced/Widowed

1833

89.4

3024

83.6

4857

85.7

< 0.001

 Married

218

10.6

595

16.4

813

14.3

Living location

 Rural areas

1408

68.1

2229

61.1

3637

63.7

< 0.001

 Town

254

12.3

519

14.2

773

13.5

 Urban/Mountainous/Island

406

19.6

898

24.6

1304

22.8

Occupation

 Student

1688

81.7

2810

77.1

4498

78.8

< 0.001

 Nurse, technician

147

7.1

344

9.4

491

8.6

 Doctor

194

9.4

380

10.4

574

10.1

 Other

36

1.7

110

3.0

146

2.6

Mean income/month

 Under 5 million VND

1693

84.8

2865

80.6

4558

82.1

< 0.001

 5–10 million VND

221

11.1

522

14.7

743

13.4

 10 million VND or above

82

4.1

167

4.7

249

4.5

Monthly household income per capita

 Under 5 million VND

1076

52.7

1674

46.3

2750

48.6

< 0.001

 5–10 million VND

601

29.5

1255

34.7

1856

32.8

 10 million VND or above

363

17.8

685

19.0

1048

18.5

Type of workplace

 Student

1398

67.7

2321

63.7

3719

65.2

< 0.001

 University hospital

354

17.2

608

16.7

962

16.9

 General hospital

175

8.5

446

12.2

621

10.9

 CDC/Medical center/Public health station

86

4.2

178

4.9

264

4.6

 Other

51

2.5

88

2.4

139

2.4

Levels of health facilities

 National Hospital

155

7.5

346

9.5

501

8.8

0.04

 Provincial/city hospital

715

34.8

1216

33.5

1931

33.9

 University hospital

1116

54.3

1977

54.4

3093

54.4

 Other

68

3.3

96

2.6

164

2.9

Working experience

 Students

1424

69.1

2379

65.3

3803

66.6

< 0.001

 < 1 years

108

5.2

136

3.7

244

4.3

 1–5 years

320

15.5

542

14.9

862

15.1

 More than 5 years

210

10.2

587

16.1

797

14.0

Having part-time job

298

14.5

468

13.0

766

13.5

0.10