Board of Scientific Counselors - Presentations

September 17-18, 2007

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NIS & SLAITS Program Overview: National Immunization Survey

PowerPoint PresentationCdc-ppt [PPT, 1.1 MB]

Slide 1

NIS & SLAITS Program Overview:
National Immunization Survey

NCHS BSC Meeting
September 17, 2007
James A. Singleton, M.S.
Chief, Assessment Branch
Immunization Services Division
NCIRD/CDC

Slide 2

Outline

• History of the NIS
• Purpose
• Methods
• Resources
• Information Dissemination
• Proposed objectives of program review

Slide 3

Development of the U.S. Immunization Program

• Vaccination Assistance Act, 1962
  • Established Section 317 grant program
• Childhood Immunization Initiative, 1977
  • Focus on enacting school entry laws
• Vaccine coverage monitoring, 1957-91
  • U.S. Immunization Survey, CPS
    • Parental report of vaccinations
    • Dropped after 1985; cost, validity concerns
  • Retrospective school surveys, 1985-91

Slide 4

Polio, DTP, Measles-Containing Vaccination Coverage Levels: 1959-1990, U.S. Immunization Survey

Slide 5

U.S. Measles Resurgence
1989-1991

• Cases 55,622
• Age group affected < 5 yrs
• Hospitalizations > 11,000
• Deaths 132
• Direct medical costs > $150 million

Slide 6

Childhood Immunization Initiative (CII), 1993

• Achieve 90% coverage for preschool children
• Vaccines for Children Program
  • Entitlement program funded by Medicaid
  • ACIP recommendations translated into appropriations
• Increase in Section 317 funding
• Funding for the National Immunization Survey (NIS)
  • Created in 1994 to measure coverage goals of the CII by state and selected urban areas
• NHIS NIPRCS 1994-1999
  • National provider-reported data on vaccination of children 19-35 mo
  • Used in NIS weighting adjustments for households without telephones

Slide 7

Mission

• National Center for Immunization and Respiratory Diseases (NCIRD)
  • Prevent disease, disability and death through immunization and by control of respiratory and related diseases
• Immunization Services Division
  • Protects individuals and communities from vaccine-preventable diseases through provision of federal funds and contracts to purchase vaccine, the provision of technical and financial support of immunization programs, provider and public education, evaluation and research

Slide 8

Slide 9

What gets measured – gets done

Notes: The National Commission on Prevention Priorities guided an update to 2001 ranking of clinical preventive services. Rankings were based on two measures: clinically preventable burden and cost-effectiveness. The top three ranked preventive services included the childhood immunization series.

Slide 10

Purpose of CDC Vaccine Assessment

• Overarching goal – facilitate program improvement and behavior change leading to increased vaccination levels, thus reducing health and societal impact of vaccine-preventable diseases (VPD’s)
• Need vaccine assessment system for immunization programs
  • Children < 3, 4-6, 11-18 years
  • Adults

Slide 11

Purpose of CDC Vaccine Assessment

• Evaluate effectiveness of immunization grant programs over time
• Help with allocation of Vaccines for Children (VFC) program resources
• Monitor progress toward national Healthy People objectives
• Build and maintain support for national & state immunization programs

Slide 12

Purpose of CDC Vaccine Assessment

• Identify subgroups at higher VPD risk
• Identify facilitators & barriers to vaccination to improve interventions
• Evaluate implementation of vaccine recommendations from the Advisory Committee on Immunization Practices (ACIP)
• Assess differential impact of vaccine shortages
• Evaluate uptake of new vaccines

Slide 13

Purpose of CDC Vaccine Assessment

• Assist in evaluating health impact of vaccination
  • Proxy for immunity
  • Ecologic analysis of trends
  • Vaccine effectiveness studies
  • Vaccine safety studies
• Emergency preparedness
  • Influenza pandemic monitoring

Slide 14

Designing a Vaccine Coverage Assessment System

• Target population
• Sampling method
• Vaccines assessed
• Auxiliary data collected
• Geographic specificity
• Periodicity of data collection and reporting
• Timeliness (vaccination to data availability)
• Comparability across areas and over time
• Representativeness
• Accuracy
• Resources

Slide 15

Overview of the National Immunization Survey (NIS)

Slide 16

Target Population

• Noninstitutionalized children aged 19-35 months at time of telephone interview

Slide 17

Sample Design

• Stratified, two phase survey:
  • List-assisted, random-digit-dialing survey to identify age-eligible children
    • Spanish interviewers & CATI version
      • 9% of 2005 interviewers conducted in Spanish
    • Language Line Services used for 187 interviews (0.67%) in 2005
  • Mailed survey to providers identified during telephone interview to collect provider-reported vaccination histories

Slide 18

Slide 19

Vaccines

• All ACIP recommended vaccines that children should have received by 19 months of age

Slide 20

Slide 21

Demographics and Other Data Collected

• Household
  • Race/ethnicity of mother, child
  • Mother’s age, education, marital status
  • Family income
  • Health insurance
  • WIC participation
  • Shot card available
  • Breastfeeding
• Providers
  • # physicians at practice
  • Facility type
  • VFC provider

Slide 22

NIS Special Purpose Supplements (Topical Modules)

• Subsamples of NIS survey can be asked special-purpose questions
  • Insurance Status (2001-02; 2006+)
  • Day Care and Breast Feeding (2001-02)
  • Attitudes and Beliefs (2001-02)
  • Vaccine Safety (2003-04)
  • Vaccine Shortage (2003-04)
  • Childhood Influenza (2004)
  • SES (planned 2008)
  • Parental concerns (planned 2008)

Slide 23

New NIS Modules

• Develop 2007, collect data 2008
• SES Module (national)
  • Barriers to immunization
  • Factors associated with racial/ethnic and income-related coverage disparities
  • Add key questions to NIS core later
• Parental Concerns Module
  • Early warning system for parental concerns about vaccination
  • Developed with NVAC Subcommittee on Public Engagement
  • Consider periodic state-specific estimates

Notes: Past NIS modules have addressed parent safety concerns, deferral of vaccination in a shortage, influenza vaccination of young children. We are also interested in ideas for future modules for the 2009 NIS.

Slide 24

Geographic Specificity

• National level
• State level
• City level
  • Six cities receiving Section 317 immunization grant funding
• Other city/county areas
  • chosen/funded by state grantees
  • Eight areas chosen for 2007

Slide 25

NIS is More Than One Survey…

Slide 26

Periodicity

• Conducted continuously based on quarterly samples
• Reported biannually based on data delivered in June and December
• Focus on data reporting each summer using calendar year data

Slide 27

Timeliness

• Average time from vaccination to delivery of calendar year data (months):
  • 38m for HepB birth dose (range 25-52m).
    • (19m in Dec + 6m till data deliv. = 25)
    • (34m in Jan + 12m data col. y + 6m till data deliv. = 52)
  • 32m for 3rd Rota (range 19-46m).
  • 26m for MMR1, VAR1 (range 13-40m).
  • 19m for DTaP4 (range 6-33m).
  • 17m from end of flu vacc. Period (Jan)

Slide 28

Comparability

• Same methods and contractor conduct survey in all sampling areas
• Sample size chosen to achieve effective sample size of 180 children with adequate provider data in each area
• 95% CI half-width of 7.5% or less
• Comparability of methodology means estimates are comparable among states and urban areas over time

Slide 29

Representativeness

• Data weighted to account for households without landline phones and for nonresponse
• In Q1/Q2 of 2006, 10.4% of children in US lived in HH w/o landline phones
• Research underway to possibly improve the noncoverage adjustments

Slide 30

NIS 2005 Sample

Total sample released – 4,465,261
Resolved sample – 3,721,224 (83%)
Households identified – 1,085,040
Households screened – 1,006,435 (93%)
Eligible households – 31,909 (3.2%)
Complete interviews – 26,867 (84%) 27,627 children
Children with adequate Provider data – 17,448 (63%)

Slide 31

Wireless Substitution: Preliminary Data from the 2006 National Health Interview Survey

Slide 32

Accuracy

• Parental report of childhood vaccination has been shown to be unreliable
• For all NIS estimates, only provider-reported vaccinations are used for estimation of vaccine coverage

Slide 33

Slide 34

NIS-Teen

• Children aged 13-17 years at time of telephone interview with parent
• Vaccination histories from providers
• Measures vaccinations ages > = 11 years
• Conducted national survey Q4 2006
  • 5,483 completed interviews
• Repeat Q4 2007
• Expansion to state/grantee level survey high priority for 2008

Slide 35

Strengths of the NIS

• States and selected city/county areas use estimates for program improvement
• Comparability of methodology means estimates are comparable among states and urban areas over time
• Identifies areas, populations and factors associated with under-immunization
• Provider-verified results
• Provides sampling frame for other health surveys (SLAITS)

Slide 36

Challenges for NIS

• Declining telephone survey response rates – 87% (1994) to 64.5% (2006)
• Wireless-only households
• Some non-coverage and non-response bias may remain after weighting adjustments
• Increasing costs

Slide 37

NIS Operational/Methods Research

• Research to decrease bias, increase cost-efficiency, and guide future NIS methodology
  • Use of IIS sample frame & age-targeted phone lists, 2+ phone banks, redesign questionnaire, advance letter, calling rules, answering machine messages, sensitivity analysis model to evaluate potential bias
• Research to address wireless only and phoneless households
  • Analysis of NHIS by phone status
  • Pilot studies calling cell phones

Slide 38

NIS and Immunization Information Systems (IIS)

• “The quality and completeness of the registry data must be improved and must be comparable across all states before consideration may be given to supplement or replace the provider-reported data in the NIS.”
  – Khare et al., Arch Pediatr Adolesc Med 2006
• NIS provider question on use of IIS to obtain vaccination histories (2006)
• Offering service to grantees to evaluate IIS via match with NIS sample

Slide 39

NIS and Immunization Information Systems (IIS)

• Conducting NIS survey & provider record check on IIS sample in 2 states
  • Dual frame approach may reduce cost, increase validity
  • Evaluate use of provider record check on IIS sample to estimate local vaccination coverage
  • Evaluate non-response bias in the RDD frame using IIS data as “gold” standard
• Encourage use of IIS for local assessment

Slide 40

Vaccine Assessment Funding Sources (FY07)

• Total $23.3m
  • < 1% of annual $2.5b VFC vaccine purchase
• $12.8m PHS Evaluation
• $ 7.7m Vaccines for Children Program
  • Additional VFC $ for NIS-Teen, FY08
• $ 1.4m state Section 317 grants
  • NIS oversampling in areas chosen by state
• $ 0.9m Division (ISD) research funds
• $ 0.6m influenza pandemic planning

Slide 41

Vaccine Assessment Funding Allocation (FY07)

• $20.5m NIS contract (NORC)
  • $12.2m core NIS
  • $ 2.2m NIS-Teen
  • $ 2.7m modules (adult, SES, Concerns)
  • $ 1.5m operational/methods research
  • $ 1.4m NIS oversampling in selected areas
  • $ 0.6m influenza pandemic survey module
• $ 1.1m IAA’s with NCHS
  • Support of NHIS immunization questions
  • NCHS staff support of NIS (~1.5 fte)
• $ 1.7m other assessment activities

Slide 42

Vaccine Assessment Staff Resources

• Assessment Branch (AB), ISD/NCIRD
  • 14 FTE’s, 3 contractors
    • Statisticians, epidemiologists, health scientists
    • ~ 9 FTE-equivalents devoted to NIS
• NCHS (~1.5 FTE)
  • NIS contract originally managed by NCHS
  • Effective 2005, co-project officers established
    • AB/ISD responsible for NIS
    • NCHS responsible for SLAITS
      • Also handles NIS IRB
  • Statistician
    • Methods research, public use file development

Slide 43

Information Dissemination

• Annual MMWR articles
  • Briefings with states/local grantees
• Post detailed tables online twice yearly
  • Q3-4 2005 + Q1-2 2006 data ~ Jan. 2007
  • Q1-4 2006 data ~ summer 2007
• Public use file available annually
• In-house analysis
  • 13 NIS papers published in 2006
• Ad hoc requests from states, CDC, other
• Developing online data query system

Slide 44

Uses of NIS Data

• State immunization program improvements
• Assist in management of the Vaccines for Children (VFC) entitlement program (health insurance)
• Monitoring Healthy People 2010 objectives
• Uptake of new vaccines
• Factors associated with coverage
• Racial/ethnic disparities
• Parental vaccine safety concerns
• Quality performance measures
  • timeliness, age-appropriate & validly-spaced doses
• Use of combination vaccines
• County-level coverage estimation
• Coverage trends by birth cohort
• Cost-effectiveness analysis
• Vaccine-effectiveness studies

Slide 45

Strategic Planning

• April 2007 External Review of Intramural Research
  • Prioritization of vaccination assessment
    • “What should we be assessing?”
• CDC vaccination assessment work group
• Feedback on priorities
  • National Vaccine Advisory Committee
  • Immunization stakeholders
• October 2007 CCID BSC NCIRD subcommittee
  • Issues in data analysis and reporting

Slide 46

NCHS Program Review Proposed Questions

• What could be done to improve the validity and efficiency of the NIS?
• Are we conducting the appropriate types of methods research to guide improvement of the NIS?
• How should we deal with increasing prevalence of households with only cell phones?
• What alternative sampling designs should be considered?

Slide 47

Additional Slides

Slide 48

Vaccine-Specific Coverage: Preschool-Aged Children

Slide 49

Trends in Vaccine Coverage in Vermont, NIS 2000-2006

Slide 50

Estimated PCV7 Coverage (3+ doses), by State, National Immunization Survey, U.S., 2004

Slide 51

Data Analysis & Reporting

• Reporting coverage for vaccine series
• Defining vaccination outcome
• Other measures of coverage
  • Timeliness
  • Cumulative % vaccinated by age
• Trends by birth cohort vs. data collection year
• Small area estimation
  • Estimates for 181 counties using data from 2004-05 combined