Maternal Immunization in the U.S.: A Nationwide Retrospective Cohort Study

Abstract

Introduction: At present, pregnant women in the U.S. are recommended to receive tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) and influenza vaccines. This study assessed maternal coverage of these 2 vaccinations.

Methods: Data for this retrospective cohort study were extracted from 2 large administrative claims databases, the MarketScan Commercial and Multi-State Medicaid Databases, for 2009-2017 and analyzed in 2018. Women aged 15-44 years on the date of pregnancy end were included. Pregnancies with gestational age of less than 23 weeks were excluded from the Tdap vaccination endpoint owing to the optimal recommended gestational age for Tdap vaccination. Multivariable logistic regression models identified predictors of vaccination.

Results: The Tdap vaccination subpopulation included 1,421,452 Commercial and 523,635 Medicaid pregnancies; the influenza vaccination subpopulation included 1,862,705 Commercial and 628,079 Medicaid pregnancies. There were marked increases in vaccination coverage from 2010 to 2017: from 1.0% to 56.3% (Commercial) and from 0.5% to 31.4% (Medicaid) for Tdap, and from 14.7% to 31.3% (Commercial) and from 9.7% to 17.5% (Medicaid) for influenza. The likelihood of Tdap/influenza vaccination increased significantly with receipt of the other vaccine and more pregnancy-related healthcare visits.

Conclusions: Although maternal Tdap and influenza vaccination coverage increased substantially from 2010 to 2017 among large, geographically diverse U.S. cohorts, coverage remained suboptimal, potentially putting newborns at risk of pertussis and influenza. Strategies to increase maternal vaccination coverage could target women identified to have a reduced likelihood of vaccination: those who are younger, black, residing in rural areas, with multiple gestation, and a prepregnancy inpatient admission.