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Table 1 Characteristics of medical enrollees, cohort enrollees, participation refusers, and those never reached for cohort invitation in study year one (2010–11)

From: Factors associated with recruitment, surveillance participation, and retention in an observational study of pregnant women and influenza

 

A

B

A vs. B

C

A + B vs. C

D

A + B + C vs. D

Cohort Enrollees

Medical Enrollees a

Medical vs. Cohort Enrollees

Reached but Refused to Participate

Medical and Cohort Enrollees vs. Refused

Never Reached for Participation Invite

Never Reached vs. Reached (Enrolled + Refused)

Total N

1374

98

 

5564

 

6717

 

Source: Medical Record, Categorical Variables, N (Col. %)

 Study Site

  

p < .0005

 

p < .0005

 

p < .0005

  Site 1

565 (41)

16 (16)

 

1248 (22)

 

786 (12)

 

  Site 2

809 (59)

82 (84)

 

4316 (78)

 

5931 (88)

 

 Race (White)

  

p < .0005

 

p < .0005

 

p < .0005

  White

934 (68)

46 (47)

 

3304 (59)

 

3822 (57)

 

  Non-White

440 (32)

52 (53)

 

2037 (37)

 

2689 (40)

 

  Unknown Race

   

223 (4)

 

206 (3)

 

 Ethnicity

  

p < .0005

 

NA b

 

NA b

  Hispanic/Latina

173 (13)

27 (28)

 

1114 (20)

 

1802 (27)

 

  Non-Hispanic

1201 (87)

71 (72)

 

2213 (40)

 

2375 (35)

 

  Unknown Ethnicity

   

2237 (40)

 

2540 (38)

 

 High Risk Medical Conditions

  Chronic Condition (prior to pregnancy)

277 (20)

21 (21)

p = .76

581 (10)

p < .0005

731 (11)

p = .007

  Pregnancy Complication

1034 (75)

89 (91)

p < .0005

3567 (64)

p < .0005

4292 (64)

p = .001

 Medical visits for ARI (1 or more)

  Year Prior to Study (12 months)

320 (23)

38 (39)

p = .001

925 (17)

p < .0005

1075 (16)

p = .33

  During Study Period (6 months)

307 (22)

98 (100)

p < .0005

953 (17)

p < .0005

850 (13)

p < .0005

 Study Season’s Influenza Vaccination

1038 (76)

53 (54)

p < .0005

3029 (54)

p < .0005

3533 (53)

p < .0005

Medical Record, Continuous, Mean (95% CI)

 Woman’s Age (at start of season), Years c

  Both Sites

31.7 (31.4–31.9)

29.9 (28.7–31.1)

     

  Site 1

30.6 (30.1–31.0)

28.1 (26.8–29.4)

 

29.1 (28.8–29.4)

 

28.9 (28.5–29.3)

 

  Site 2

32.4 (32.1–32.7)

30.3 (29.7–31.0)

 

31.4 (31.2–31.5)

 

31.4 (31.3–31.5)

 

 Gestational Age (at start of season), Days c

  Both Sites

179 (176–182)

184 (172–196)

     

  Site 1

155 (151–160)

159 (146–172)

 

132 (127–138)

 

134 (127–141)

 

  Site 2

199 (195–202)

178 (171–185)

 

168 (166–173)

 

166 (164–168)

 

Source: Enrollment Interview, Categorical, N (Col. %)

 Race (Self-Reported)

  

p < .0005

    

  White

934 (68)

46 (47)

     

  Asian

205 (15)

19 (19)

     

  Black

64 (5)

5 (5)

     

  Mixed or Other

171 (12)

28 (29)

     

 Marital Status

  

P = .009

    

  Married or Partnered

1286 (94)

85 (87)

     

  Not Married and Not Partnered

88 (6)

13 (13)

     

 Education

  

p < .0005

    

  High school or less

119 (9)

19 (19)

     

  Some college or bachelor’s degree

744 (54)

64 (65)

     

  Advanced degree

511 (37)

15 (15)

     

 Subjective social status

  

p = .002

    

  1 to 3 (low)

25 (2)

5 (5)

     

  4 to 6 (medium)

697 (51)

63 (64)

     

  7 to 9 (high)

632 (46)

28 (29)

     

  Missing or refused

20 (1)

2 (2)

     

 Child(ren) aged < 13 years at home

  

p = .049

    

  No

644 (47)

36 (37)

     

  Yes child

730 (53)

62 (63)

     

 Self-rated Health Status

  

p < .0005

    

  Poor, fair, or good

301 (22)

46 (47)

     

  Very good

548 (40)

32 (33)

     

  Excellent

525 (38)

20 (20)

     

 Smoking

  

p = .23

    

  Never smoked

1016 (74)

67 (68)

     

  Previously or currently smoke

358 (26)

31 (32)

     

 Stressful events in past year (0–17)

  

p = .11

    

  0

276 (20)

11 (11)

     

  1

349 (25)

24 (24)

     

  2

310 (23)

23 (23)

     

  3 or more

439 (32)

40 (41)

     
  1. Abbreviations: NA Not applicable, ARI Acute respiratory illness; ICD-9-CM codes 460–466 and 480–488
  2. aMedical enrollees are women who were recruited by telephone following a medical visit for ARI
  3. bWe did not calculate a statistical comparison for ethnicity with the study refusers and never reached women given the large number with unknown ethnicity in the medical records; the comparison of medical vs. cohort enrollees relied on self-reported ethnicity
  4. cWomen’s age and age of fetus were calculated using a common reference date, which was the start of the influenza season at each study site. Age was calculated combining sites for fully enrolled women, but had to be calculated by study site for women not enrolled
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BMC Pregnancy and Childbirth

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