Assessment of Tdap Vaccination for Pregnant Women Enrolled in Michigan Medicaid

BACKGROUND: In October 2011, the Advisory Committee on Immunization Practices (ACIP) first routinely recommended the administration of Tdap (tetanus, diphtheria and acellular pertussis) vaccine during pregnancy. By vaccinating pregnant women, maternal antibodies are transferred in utero and provide passive immunity to infants, who are at highest risk of mortality and morbidity from pertussis. Since this recommendation, few studies have assessed Tdap coverage for pregnant women. We used Michigan Medicaid claims data to compare Tdap vaccination percentages during pregnancy before and after the 2011 ACIP recommendation, and we assessed disparities in vaccinations after the 2011 recommendation.

METHODS: To identify pregnant women, we linked birth certificates for infants born January 1, 2008–March 22, 2013 to maternal Medicaid claims data. Women receiving full Medicaid benefits and delivering their first live-birth between ages 10–60 were included in the study. We used ICD-9 procedural codes and CPT codes to capture Tdap vaccination events. We also examined whether maternal age, race or ethnicity impacted vaccination after the recommendation. Data from Michigan’s immunization information system supplemented Medicaid data.

RESULTS: A total of 69,056 pregnant women were included in the study. Tdap vaccination percentages before and after the 2011 ACIP recommendation were 3.4% and 13.8%, respectively (p<0.001). After the 2011 recommendation, younger women, ages 10–17, were less likely to receive a prenatal Tdap vaccine (10.2%) compared to women ages 18–34 (14.3%; p<0.001); 15.4% of women, ages 35-60, received the vaccine during pregnancy. 8.6% of Black women and 10.2% of Asian women were vaccinated compared to 16.8% of White women (p<0.001). Among Native Americans, 20.7% of women received a prenatal Tdap vaccine. Women of Arab ethnicity had fewer vaccination events than Hispanic women (7.2% vs. 14.2%; p<0.001).

CONCLUSIONS: Tdap vaccination during pregnancy increased significantly after the 2011 ACIP recommendation among women enrolled in Medicaid. Age disparities for younger women may indicate that these women received the recommended adolescent dose of Tdap and would not require another dose during pregnancy. Vaccinations prior to or immediately after pregnancy were not captured in this study. Racial disparities in vaccinations have been documented for other vaccines. In recognition of the importance of Tdap administration during pregnancy, ACIP revised the recommendation to include a Tdap dose during every pregnancy (February 2013). Increased education for healthcare providers, parents, and families is necessary to help expand knowledge of and adherence to ACIP recommendations.