Matching enhances IIS data assessing Tdap and influenza vaccine uptake during pregnancy in Washington State

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1 Matching enhances IIS data assessing Tdap and influenza vaccine uptake during pregnancy in Washington State Joanna Eavey, MSPH - joanna.eavey@doh.wa.gov AIRA IIS National Meeting April 5 7, 2016

2 Background National increases in pertussis; WA pertussis epidemics in 2012 and 2015 Influenza vaccine recommended for all pregnant women during each pregnancy in any trimester Tdap recently recommended during every pregnancy at weeks gestation to best protect infants 0 2 months of age Difficult to assess vaccine uptake in pregnancy and lack of published studies Need for reliable, easily reproducible, population survey methods

3 Background research questions 1. Is there an easy, reliable way to measure uptake of Tdap and influenza vaccines during pregnancy? 2. What percentage of Washington women receive Tdap and influenza vaccines during pregnancy as recommended?

4 Methods - Data sets used WA birth certificates (BCs) Mother s identified information from January 2015 deliveries ~88,000 annual deliveries in WA Virtually 100% capture Fields used: Mother's names (first, middle, legal last, maiden) Mother's DOB Mother's ZIP code of residence

5 Methods Data sets used WA Immunization Information System (IIS) Patient records for all females ages years as of 1/31/2015 Voluntary immunization registry >80 million records for >8 million people Fields used: Patient's names (first, middle, last) Patient's DOB Patient's ZIP code of residence

6 Methods - Matching methodology Matched performed using a series of Statistical Analysis System (SAS) v.9.4 programs Create campics in both input data sets Campic = combinations of identifying information Examples: DOB + first name, DOB + legal name, first name + legal name Match campics from each input data set, assign a score based on match fitness Output results based on match fitness fall into three categories: True matches -- accepted Maybe matches output for manual review Non-matches -- discarded

7 Methods - Data cleaning

8 Results Match rate We started with 7,184 WA birth records from Jan 2015, representing 6,990 unique mothers (114 multiple births). Of these, 3,711 matched to an IIS patient record. 3,881 total match pairs and 3,711 unique mothers Difference due to duplicate IIS records Total match rate = 53.0% of women who delivered an infant in January 2015

9 Results Vaccinations 33,852 total vaccination records for 3,711 matched mothers Vaccine Total vaccination records (valid and before 2/1/2015) # records per matched mother % matched mothers vaccinated during pregnancy % matched mothers vaccinated at weeks Tdap 3, % (N= 1,451) 31.4% (N=1,164) Influenza 4, % (N=1,209) N/A

10 Results Vaccinations 80% (1,164/1,451) of matched mothers who received Tdap during pregnancy received it during the recommended time period. Of the 1,164 matched mothers who received a Tdap between weeks gestation, 67% also received a flu vaccine. Of the 2,547 matched mothers who did not receive Tdap during pregnancy, 43% had previously received a Tdap vaccination.

11 Percentage of matched mothers with a Tdap vaccination between 27 and 36 weeks gestation, by county Range: 0% - 63% of mothers vaccinated between 27 and 36 weeks gestation. Similar pattern for flu (not shown). Includes all counties with >4 matched mothers.

12 Hospital delivery volume vs. Tdap vaccination rates for delivering mothers Percent vaccinated with Tdap at weeks 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% = 1 hospital Range: % Number of matched mothers delivering at hospital

13 Percentage of matched mothers vaccinated with Tdap between weeks gestation and influenza during pregnancy by race/ethnicity Percent vaccinated 60% 50% 40% 30% 20% 10% Tdap Flu 43% 38% 38% 37% 47% 51% 34% 37% 28% 28% 33% 50% 40% 47% 0% Asian Black Hispanic Native American (N= 442) (N= 289) (N= 186) (N= 107) White Other Unknown (N= 2,585) (N= 13) (N= 89)

14 Maternal age vs. Tdap and influenza vaccination rates 50% Tdap Flu Percent vaccinated 40% 30% 20% 10% 37% 41% 34% 34% 28% 28% 30% 33% 37% 38% 27% 32% 40% 20% 0% Under Over 45 (N= 287) (N= 983) (N= 1,116) (N= 916) (N= 332) (N= 56) (N <10) Maternal age at delivery (years)

15 Gestational age at delivery vs. Tdap and flu vaccination rates 50% Percent mothers vaccinated 40% 30% 20% 10% 49% 21% 43% 28% 26% 32% 31% 33% 34% Tdap 32% 30% Flu 13% 10% 0% 6% Extremely preterm Very preterm Late preterm Early term Full term Late term Post term 37-<39 wks 39-<41 wks 41-<42 wks >=42 wks <28 wks 28-<32 wks 32-<37 wks Estimated gestational age at delivery

16 Discussion We found 31.4% (N=1,164) of pregnant mothers received a Tdap at weeks gestation, as recommended. 32.3% (N=1,209) received a flu shot during pregnancy. WA Tdap coverage is higher than that found in most other studies; flu coverage is lower. Higher vaccine coverage was associated with nonwhite mothers, mothers <25 years-old and years-old, mothers who deliver preterm infants (flu) and full term gestational age of infant (Tdap).

17 Vaccine Coverage comparisons Tdap ; USA 18, % PRAMS Tdap ; WA state % PRAMS Tdap Nov Feb 2013; MI Medicaid enrollees 15, % MI study 2 Tdap ; USA N/A 14.4% Tdap Time frame and population of pregnant women Jan Nov ; women insured through seven health systems Tdap Jan 2015; WA state 3,707 N Coverage during pregnancy CDC internet panel survey 3 438, % Kharbanda et al % during pregnancy 31.4% at wks Data source Influenza ; USA 18, % PRAMS 1 Influenza ; WA state % PRAMS Influenza Jan 2015; WA state 3, % This study This study 1. PRAMS CDC. 2. Housey M et al. Vaccination with tetanus, diphtheria, and acellular pertussis of pregnant women enrolled in Medicaid Michigan, MMWR. 63(38); Bridges CB. Improving immunization of adults. Presentation available at: Accessed 3/3/ Kharbanda EO et al. Maternal Tdap vaccination: coverage and acute safety outcome in the vaccine safety datalink, Vaccine Feb 10;34(7):

18 Limitations and advantages Limitations: Underestimate of true coverage reporting is voluntary and adult immunization reporting is lower in IIS Potential differential capture of immunizations by demographic (ex: maybe less likely to capture immunizations provided in smaller clinics, rural geographies, maybe less likely to match mothers in areas with large immigrant populations) Did not capture insurance status Advantages: Population based methodology includes all statewide delivering mothers Reproducible methodology Data are already reported to WA DOH No additional chart review or other data needed SAS programs are developed Little cost to program, other than time for manual review

19 Conclusions WA state has higher Tdap coverage than reported in similar studies, although coverage remains low. WA state could have lower influenza coverage than reported in similar studies. This study shows that population measurement of immunization coverage among pregnant women is possible in jurisdictions with robust adult IIS records. Next steps: repeat with more years of data and more demographic variables.