Surveillance of seasonal influenza vaccination coverage among pregnant women and health care personnel in the United States Sara M.A. Donahue, DrPH, MPH,

Surveillance of seasonal influenza vaccination coverage among pregnant women and health care personnel in

the United States

Sara M.A. Donahue, DrPH, MPH,1 Carla L. Black, PhD, 2 Stacie M. Greby, DVM, MPH,2 Helen Ding, MD,2 Anup Srivastav, DVM, PhD,2 David Izrael, MS,1 Sarah W. Ball, MPH, ScD,1 Charles DiSogra, DrPH,3 Deborah K. Walker, EdD,1 Rachel Martonik, BS3

National Center for Immunization & Respiratory Diseases

Assessment Branch/Immunization Services Division

1 Abt Associates Inc., Cambridge, Massachusetts2 Immunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention3 Abt SRBI, New York, New York

Background

CDC uses national surveillance data to inform activities for promoting influenza vaccination and monitoring the effectiveness of vaccination efforts

Two special populations of interest are pregnant women and health care personnel (HCP) Pregnant women are at increased risk of influenza-

related severe illness and hospitalization Routine vaccination of HCP can help reduce influenza-

related illness among HCP and in health care settings

2

Background (cont)

The relatively low prevalence of these two groups in the U.S. general population makes it difficult to survey a sufficient number of respondents in a short time frame using general population surveys Vaccination coverage data are needed during and

immediately following each influenza season to inform public health acitivities in current and future influenza seasons

Existing surveillance systems do not provide timely data and do not not capture in-depth information regarding vaccine-related knowledge, attitudes, and behaviors (KAB) that are specific to pregnant women or HCP specific detailed information related to pregnancy or

occupation may not be available

3

Background (cont)

The CDC has used non-probability based internet panel surveys to monitor infleunza vaccination coverage among HCP (since the 2009-10 influenza season) and pregnant women (since the 2010-11 influenza season)

4

Objectives

To describe the methodology of the Internet panel surveys

To compare the methodology and results of the Internet panel surveys to those of existing national probability-based surveys Results of the HCP internet panel surveys will be

compared to the National Health Interview Survey (NHIS) Results of the pregnant women internet panel surveys

will be compared to the Behavioral Risk Factor Surveillance System (BRFSS) and the Pregnancy Risk Assessment Monitoring System (PRAMS)

Methodology – Internet panel survey (HCP)

Large-scale opt-in web-based survey of HCP in the United States (n ~2000 HCP each survey)

Sample Sources:

Professional HCP (physicians, nurse practitioners, physician's assistants, nurses, dentists, pharmacists, allied health professionals, technicians, and technologists) sample from WebMD Internet portal with >2.5 million U.S. members.

Other Support HCP (assistants, aides, administrators, clerical support workers, janitors, food service workers, and housekeepers) sample from Survey Sampling International, a general population panel of >1 million U.S. households.

Panelists recruited by email invitation and intercept method

Methodology – Internet panel survey (HCP)

Self-administered online survey

Administered twice during each influenza season (November and April) Data from April survey are used to generate coverage

estimates for the entire influenza season

Post-stratification weighting to estimate the national population of HCP Weighted by age groups, gender, race/ethnicity,

occupational settings, and census regions

No statistical testing performed since sample is non-probability based 5 percentage points used as notable difference

Comparison of survey methodologies (HCP)

Internet panel survey NHIS

Recruitment methodNon-probability sample from a volunteer Internet panel

Complex sampling design involving stratification, clustering, and multistage sampling

Survey mode Self-administered online In-person interview

Timing of influenza vaccination

During flu season Within past 12 months*

Geographic level National National

Data collection schedule

Nov and April of each flu season

Monthly

Timeliness of reporting

2 weeks 16 months

Typical response/completion rate

90% 61%

Approx. sample size 2000 per survey 2000* Since 2005 can determine whether during influenza season

Comparison of survey demographics – Internet panel survey and NHIS

9

18-29 30-44 45-59 60+0

10

20

30

40

50

60

70

80

15.1

34.5

39.7

10.6

21.6

31.1 32.0

15.3

IPS NHIS

Final weighted distribution of age groups in HCP sample 2011-12 influenza season,

Internet Panel Survey vs. NHIS

Age groups in years


10

Hisp White, non-Hisp Black, non-Hisp Other0

10

20

30

40

50

60

70

80

10.6

66.7

13.49.310.8

68.4

13.17.7

IPS NHIS

Racial /ethnic groups

Final weighted distribution of racial/ethnic groups in HCP sample 2011-12 influenza season,



11

HS or less College degree More than college0

10

20

30

40

50

60

70

80

51.7

26.721.7

63.1

20.616.3

IPS NHIS

Education levels

Final weighted distribution of education levels in HCP sample2011-12 influenza season


Estimated Influenza Vaccination Coverage, Healthcare Personnel, United States, 1996-

2013

1996-97

1997-98

1998-99

1999-00

2000-01

2001-02

2002-03

2003-04

2004-05

2005-06*

2006-07

2007-08

2008-09

2009-10

2010-11

2011-12

2012-13

0

10

20

30

40

50

60

70

80

90

34 37 36 38 36 38 40 42

33

4447 48

5358 56

62

63 6467

72NHIS Internet Panel

Influenza Season

% V

accin

ate

d

vaccine shortage

* Methodology used to estimate influenza vaccination coverage among healthcare personnel changed during the 2005-06 season

Vaccination coverage by age – Internet panel survey and NHIS

13

18-29 30-44 45-59 60+0

10

20

30

40

50

60

70

80

90

100

63.968.8

63.8

75.7

55.755.9

62.4

78.0

IPS NHIS

Perc

en

t vaccin

ate

d

2011-12 influenza season, Internet Panel Survey vs. NHIS

Age groups in years

Vaccination coverage by race/ethnicity – Internet panel survey and NHIS

14


10

20

30

40

50

60

70

80

90

100

70.366.4 65.5

69.0

55.063.6

51.8

68.4

IPS

NHIS

Perc

en

t vacc

inate

d



Vaccination coverage by education – Internet panel survey and NHIS

15

HS or less College degree More than college0

10

20

30

40

50

60

70

80

90

100

59.5

70.0

80.1

56.7

68.371.0

IPS

NHIS

Perc

en

t vaccin

ate

d

Education


Discussion -- HCP

Internet panel survey sample was older and more highly educated than the NHIS sample Racial/ethnic distribution was similar between the samples In future, could consider calibrating the internet panel sample

to the NHIS sample

Both surveys indicated that vaccination coverage was highest among the oldest HCP and those with a college education or higher The Internet panel survey found no differences in coverage

among HCP by race, while black and Hispanic HCP had lower coverage compared to white and other HCP in the NHIS sample

While overall influenza vaccination coverage estimates from the Internet panel survey were higher than those from NHIS for each season, the trends in coverage over time were similar

16

Discussion -- HCP

Higher estimates from Internet panel survey might be attributable to: Higher percentages of older and more highly educated

HCP in the Internet panel survey sample Exclusion of HCP without Internet access from the

Internet panel survey sample Differential selection (nonresponse) bias in IPS vs. NHIS,

after weighting adjustments made

17

Methodology – Internet panel survey (pregnant women)

Opt-in web-based panel survey

Pregnant women recruited from a general population panel (www.surveyspot.com ) Approximately 1 million members Dynamic panel with members opting in and out Recruiting methods: by Email invitation and Internet intercept

Women 18-49 years who were pregnant any time since August 1st were eligible for the survey

Sampled women were weighted to represent the national population of pregnant women Weighted by age groups, race/ethnicity, geographic

distribution

http://www.surveyspot.com/

Methodology – Internet panel survey (pregnant women)

Estimation of influenza vaccination coverage Data from April survey are used to generate coverage

estimates for the entire influenza season Women pregnant from October-January included in final

season estimate Only vaccinations received before or during pregnancy

were counted as vaccinated

No statistical testing performed since sample is non-probability based 5 percentage points used as notable difference

Comparison of survey methodologies (pregnant women)

Internet panel survey

BRFSS PRAMS

Recruitment method

Non-probability sample from a volunteer Internet panel

Stratified RDD sampling of landline and cell telephones

Stratified random sampling from state birth certificate registries

Survey modeSelf-administered online

Telephone interviewMailed survey with telephone follow-up

Timing of pregnancyAt interview or since Aug 1

At interview (Use Dec-Feb interviews)

Had a live birth in past 2-6 months

Timing of influenza vaccination

During flu seasonWithin past 12 months*

During influenza season

Geographic level National National State or local

Data collection schedule

Nov and April of each flu season

Monthly Ongoing

Timeliness of reporting

2 weeks 2 months 18 months

Typical response /completion rate

90% 55% 65%

Approx. sample size 1500 per survey 400-800 per season300-1500 per state/city* Since 2008 can determine whether during influenza season

Comparison of survey demographics – Internet panel survey and BRFSS

21

18-24 25-34 35-49§0

10

20

30

40

50

60

70

80

33.1

50.5

16.3

29.5

56.5

14.0

IPS BRFSS

Final weighted distribution of age groups in pregnant women sample2012-13 influenza season,

Internet Panel Survey* vs. BRFSS†

Age groups in years

* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview§ Women in BRFSS sample were 35-44 yrs


22

Hisp White,non-Hisp Black,non-Hisp Other0

10

20

30

40

50

60

70

80

23.8

50.3

18.8

7.2

25.0

58.1

12.5

4.4

IPS BRFSS


Final weighted distribution of racial/ethnic groups in pregnant women sample 2012-13 influenza season,


* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview


23

HS or less College degree§ More than college0

10

20

30

40

50

60

70

80

51.8

36.8

11.4

71.0

29.0

IPS BRFSS

Education levels

Final weighted distribution of education levels in pregnant women sample2012-13 influenza season


* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview§ BRFSS sample includes women with college degree of higher

Comparison of survey demographics – Internet panel survey and PRAMS

24

18-20 21-24 25-29 30-34 35+0

10

20

30

40

50

60

70

80

9.9

20.8

26.121.7 21.5

8.3

22.4

28.225.9

15.3

IPS PRAMS

Final weighted distribution of age groups of women pregnant anytime between October 2010-January 2011 from 18 states in United States,

2010-11 influenza season, Internet Panel Survey vs. PRAMS

Age groups in years


25


10

20

30

40

50

60

70

80

17.0

59.1

17.9

6.0

16.6

55.1

15.712.6

IPS PRAMS


Final weighted distribution of racial/ethnic groups of women pregnant anytime between October 2010-January 2011 from 18 states in United States,

2010-11 Influenza Season, Internet Panel Survey vs. PRAMS


26

High school or less Some college College and above0

10

20

30

40

50

60

70

80

23.8

32.6

43.641.3

26.831.9

IPS PRAMS

Education levels

Final weighted distribution of education levels of women pregnant anytime between Octo-ber 2010-January 2011 from 18 states in United States,


Estimated Influenza Vaccination (trivalent) Coverage, Pregnant Women*

2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-130

10

20

30

40

50

60

70

80

27 27 27

3538 40

4338

47

55

43.943.2

50.5

BRFSS PRAMS Internet Panel

Influenza Season

% V

accin

ate

d

* Behavioral Risk Factor Surveillance (BRFSS) data from December-February interviews only, for women 18-44 years pregnant at time of interview. Internet panel survey data include women pregnant from Oct-Jan who were vaccinated before or during pregnancy. PRAMS estimates may include women vaccinated after delivery.

Vaccination coverage by age – Internet panel survey and BRFSS

28

* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview§ Women in BRFSS sample were 35-44 yrs

18-24 25-34 35-49§0

10

20

30

40

50

60

70

80

90

100

48.7 50.554.1

25.7

40.8

56.0

IPS

BRFSS

Perc

ent

vacc

inate

d

2012-13 influenza season, Internet Panel Survey* vs. BRFSS†

Age groups

Vaccination coverage by race/ethnicity – Internet panel survey and BRFSS

29


10

20

30

40

50

60

70

80

90

100

50.1 52.2

45.4

53.1

44.2

44.3 IPS

BRFSS

Perc

ent

vacc

inate

d

Racial / ethnic groups


§

* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview§ BRFSS estimate unreliable due to relative standard error >30%

§

Vaccination coverage by education – Internet panel survey and BRFSS

30

* Women pregnant any time October - January† Women interviewed December – February who were pregnant at time of interview§ BRFSS sample includes women with college degree of higher

HS or less College degree§ More than college0

10

20

30

40

50

60

70

80

90

100

43.9

57.3 58.5

31.4

56.5

IPS

BRFSS

Perc

ent

vacc

inate

d

Education


Vaccination coverage by age – Internet panel survey and PRAMS

31

18-20 21-24 25-29 30-34 35+0

10

20

30

40

50

60

70

80

41.645.1

50.254.6

52.2

41.344.4

50.1

56.3 55.9IPS PRAMS

Perc

ent

vacc

inate

d

Age groups

Influenza vaccination coverage by age groups among women pregnant any time be-tween October 2010-January 2011 from 18 states in United States,


Vaccination coverage by race/ethnicity – Internet panel survey and PRAMS

32

Hisp White, non-Hisp Black, non-Hisp Other, non-Hisp0

10

20

30

40

50

60

70

80

55.6

49.0

42.5

60.4

49.854.8

36.3

50.7

IPS PRAMS

Perc

ent

vacc

inate

d


Influenza vaccination coverage by race/ethnicity among women pregnant any time between October 2010-January 2011 from 18 states in United States,

2010-11 Influenza Season, Internet Panel Survey vs. PRAMS

Vaccination coverage by education – Internet panel survey

and PRAMS

33

High school or less Some college College and above0

10

20

30

40

50

60

70

80

42.4 43.1

58.5

44.047.3

62.0

IPS PRAMS

Perc

ent

vacc

inate

d

Education Levels

Influenza vaccination coverage by education levels among women pregnant any time between October 2010-January 2011 from 18

states in United States, 2010-11 Influenza Season,

Internet Panel Survey vs. PRAMS

Discussion – pregnant women

Compared to the Internet panel sample of pregnant women: Women in BRFSS sample were

• More likely to be 25-34 years of age• More likely to be white and less likely to be black• Less likely to have a college degree or higher

Women in PRAMS sample were• Less likely to be 35+ years• More likely to be ‘other’ race• Less likely to have a college degree or higher

34


While absolute coverage by demographic factors differed in each survey, all three surveys showed that coverage was highest among women in the oldest age categories and with a college degree or higher Both the Internet panel survey and BRFSS found no

difference by race/ethnicity in the 2012-13 influenza season

Both the internet panel survey and PRAMS found that black women had the lowest coverage in the 2010-11 influenza season

In general, overall vaccination coverage among pregnant women was lowest from the BRFSS sample and highest from the PRAMS sample


Differences in coverage estimates between surveys can be explained in part by differences in defining the cohort of pregnant women and timing of vaccination estimation The Internet panel survey includes women who were

pregnant any time from Oct-Jan. Sample includes women with a pregnancy loss and thus may have a short duration of follow-up. Vaccination status was assessed at the end of influenza season. Vaccinations received after pregnancy ended were excluded from the coverage estimates.

The BRFSS sample includes women pregnant at the time of interview for interviews conducted Dec-Feb. Vaccination status was assessed only up through the time of interview, and duration of pregnancy at the time of interview may have been short.

Discussion – pregnant women (cont) PRAMS sample includes only women who have had a live

birth and may differ from women with a pregnancy loss. Vaccination status can be assessed for the entire duration of pregnancy and influenza season. Coverage estimates include women vaccinated after delivery. • Comparing 2010-11 flu season vaccination estimates from

the same 21 states in both the Internet panel survey and PRAMS, the Internet panel survey estimate for vaccination before and during pregnancy among women pregnant any time during October 2010-January 2011 (44.9%) was similar to the estimate from PRAMS (45.6%).

Question was added to the NHIS in 2012 to identify women pregnant during peak months of influenza vaccination period These data may provide another nationally

representative sample to compare and possibly calibrate the IPS sample to

Conclusions – HCP and pregnant women

Internet panel surveys are useful for timely early season and post-season evaluation of influenza vaccination coverage among rare populations Also provide useful information regarding vaccination-

related knowledge, attitude , behaviors, and barriers (KABBs) that cannot be obtained from existing population-based surveys

Results of the Internet panel surveys should continue to be validated with results from population-based surveys

Both the HCP and pregnant women samples in the Internet panel surveys are skewed towards more highly educated respondents Consider weighting on education status in future surveys

Acknowledgements

Peng-Jun Lu Alissa O’Halloran Jim Singleton

The findings and conclusions in this presentation are those of the authors and do not necessarily

represent the views of the Centers for Disease Control and Prevention.

National Center for Immunization and Respiratory Diseases

Immunization Services Division

Surveillance of seasonal influenza vaccination coverage among pregnant women and health care personnel in the United States Sara M.A. Donahue, DrPH, MPH,

Documents

hcp internet panel surveys

age internet panel survey

online survey

survey sample sources

national population

survey sampling international

general population panel

infleunza vaccination