1. Immunization Registry and Provider-Reported Vaccination Histories: Assessing Missing Vaccinations
Linda Piccinino (Abt Associates), Meena Khare (CDC), Mike Battaglia (Abt Associates), Diana Bartlett (CDC), Lawrence Barker (CDC)

2. NIS REGISTRY DATA QUERY STUDY
Study integrated registry query consent question into standard National Immunization Survey (NIS) interview
Four mature registry sites participated in the study
Each site had one quarter of data collection (one site in Q3/2002, three sites in Q4/2002)
Vaccination history data obtained from NIS provider reports and from state/local registries for children with parental consent

3. RESEARCH PROBLEM
Need a way to assess the quality of vaccination data for NIS children with data available from both NIS provider reports and immunization registries

4. OBJECTIVES OF THIS ANALYSIS
To compare vaccination histories obtained from immunization providers and registries for a sample of NIS children months old
To examine the pattern of missing vaccination data by vaccination type, dose and source of data

5. ANALYSIS GROUPS
Sample consisted of NIS children with both registry and provider data
Data were combined for four sites because of sample size and confidentiality concerns

6. METHODOLOGY FOR IDENTIFYING MISSING VACCINATIONS
323 children with registry vaccination data (at least one shot) and adequate provider data in the NIS
Focus on DTaP vaccinations present in one source but missing from the other source
Children UTD with 4 doses of DTaP in the provider data (N = 245) but fewer than 4 doses in the registry data (N = 75)
Children UTD with 4 doses of DTaP in the registry data (N = 180) but fewer than 4 doses in the provider data (N = 16)
Determine dose number (order) of missing vaccination(s)

7. DETERMINING THE DOSE NUMBER OF MISSING VACCINATIONS
Provider data:
(1) 2/15/2001 (2) 8/12/2001 (3) 1/14/2002 (4) 9/03/2002
Registry data:
2/15/ /16/ /30/2002
For each registry vaccination date, determined which provider vaccination date was closest in time
DOSE 1 MISSING DOSE 3 DOSE 4

8. CHILDREN WITH MISSING DTaP DOSES
REGISTRY: 75 CHILDREN (30.6%) PROVIDER: 16 CHILDREN (8.9%)
Registry
Provider
MISSING
10.7% --
DOSE 4
8.0%
6.3%
DOSE 3
9.3%
12.5%
DOSE 2
2.7%
1.3%
6.7%
DOSE 1

9. CHILDREN WITH MISSING DTaP DOSES, cont’d
REGISTRY: 75 CHILDREN (30.6%) PROVIDER: 16 CHILDREN (8.9%)
Registry
Provider
DOSE 1
MISSING
DOSE 4
6.7% --
DOSE 3
5.3%
18.7%
DOSE 2
6.3%
8.0%
21.3%
50.0%
100%

10. SUMMARY OF MISSING DOSES: Dose Order
ORDER OF MISSING DOSES
Registry
Provider
First dose missing
38.7%
18.8%
Second dose missing
53.4%
43.8%
Third dose missing
49.5%
18.9%
Fourth dose missing
54.7%
62.6%

11. SUMMARY OF MISSING DOSES: Dose Frequency
NUMBER OF MISSING DOSES
Registry
Provider
One dose missing
42.7%
68.7%
Two doses missing
29.3%
18.8%
Three doses missing
17.4%
12.6%
Four doses missing
10.7%
0.0%

12. REASONS FOR MISSING PROVIDER DOSES
23 children had more registry doses than provider doses when all vaccines were examined – We reviewed the Immunization History Questionnaires (IHQs) and recontacted the providers when necessary. Extra registry vaccination dose was:
very close to another registry vaccination dose date
the last dose and was omitted from the IHQ; or that dose was administered by a provider who did not respond to the NIS
not the last dose and was inadvertently omitted when the IHQ was filled out
for a child with multiple providers but household respondent only identified one provider
for a child for whom not all identified providers responded or returned the IHQ with vaccination data

13. IMPLICATIONS FOR DATA QUALITY
INCOMPLETE VACCINATION HISTORIES
The vaccination histories were not always complete.
For children with 4 provider doses of DTaP, about 31% of children had one or more doses missing in the registry data.
For children with 4 registry doses of DTaP, only about 9% of children had one or more doses missing from the provider reports.
These suggest that registry histories tended to be more incomplete than provider histories.

14. IMPLICATIONS FOR DATA QUALITY
MIXED PATTERN OF MISSING DATA
The frequency and order of the missing doses for DTaP varied by source of data.
Therefore, source of data should be considered when interpreting results and making estimates.
The fourth DTaP dose was the most likely to be missing in both the provider and registry data, although the reasons this 4th dose was missing might differ by data source.

15. CONCLUSION Results may not be conclusive due to the small sample size.
Results showed a mixed pattern of missing doses.
Data quality concerns suggest that building combined “best value” estimates may be difficult since the quality and completeness of registry data are lacking.
Although there are data quality problems, some registries were more complete than others.
Results strongly support further research on supplementing provider- reported immunization histories with registry data in order to improve vaccination coverage estimates.

16. NEXT STEP
Future research plans include looking at the quality of registry data compared to provider-reported and household-reported vaccination data from shot cards