Maternal Tdap vaccination: Coverage and acute safety outcomes in the vaccine safety datalink, 2007–2013

Abstract

Introduction

Since October 2012, the combined tetanus toxoid, reduced diphtheria toxoid, acellular pertussis vaccine (Tdap) has been recommended in the United States during every pregnancy.

Methods

In this observational study from the Vaccine Safety Datalink, we describe receipt of Tdap during pregnancy among insured women with live births across seven health systems. Using a retrospective matched cohort, we evaluated risks for selected medically attended adverse events in pregnant women, occurring within 42 days of vaccination. Using a generalized estimating equation, we calculated adjusted incident rate ratios (AIRR).

Results

Our vaccine coverage cohort included 438,487 live births between January 1, 2007 and November 15, 2013. Across the coverage cohort, 14% received Tdap during pregnancy. By 2013, Tdap was administered during pregnancy in 41.7% of live births, primarily in the 3rd trimester. Our vaccine safety cohort included 53,885 vaccinated and 109,253 matched unvaccinated pregnant women. There was no increased risk for a composite outcome of medically attended acute adverse events within 3 days of vaccination. Similarly, across the safety cohort, over a 42 day window, incident neurologic events, thrombotic events, and new onset proteinuria did not differ by maternal receipt of Tdap. Among women receiving Tdap at 20 weeks gestation or later, as compared to their matched controls, there was no increased risk for gestational diabetes or cardiac events while venous thromboembolic events and thrombocytopenia were diagnosed within 42 days of vaccination at slightly decreased rates.

Conclusion

Tdap coverage during pregnancy increased from 2007 through 2013, but was still below 50%. No acute maternal safety signals were detected in this large cohort.

Introduction

Outbreaks of pertussis remain a persistent public health challenge across the United States and abroad [1], [2], [3], [4], [5]. Although pertussis may be mild in older children and adolescents, infants who contract pertussis are at risk for severe morbidity and mortality. These infants may be too young for vaccination and must rely on vaccination of close contacts (cocooning) and passive transfer of maternal antibodies for protection [6]. Third trimester maternal vaccination is likely to be the most effective strategy available for preventing pertussis in newborns [7], [8], [9].

The combined tetanus toxoid, reduced diphtheria toxoid, acellular pertussis vaccine (Tdap) was first recommended for routine administration during pregnancy by the California Department of Health in 2010 [10]. The Advisory Committee on Immunization Practices (ACIP) followed in 2011 with national recommendations to administer Tdap at 20 weeks gestation or later to all pregnant women not previously vaccinated [11]. In fall of 2012 the ACIP recommendations were revised, recommending Tdap administration in every pregnancy, preferably between 27 and 36 weeks gestation [12].

To date there are limited published data on receipt of Tdap among pregnant women, especially following the 2012 ACIP guidelines to administer Tdap to women in every pregnancy. In prior work by our group, among live births in 2012 across seven large health systems, less than 20% of women received Tdap during pregnancy [13]. Similarly, in the fall of 2011, data from the Pregnancy Risk Assessment Monitoring System demonstrated that, among women with live births in 16 states and New York City, 9.8% received pertussis vaccine during pregnancy [14]. More recent data from Texas and Wisconsin have demonstrated higher Tdap uptake for pregnant women in 2013 and 2014 [15], [16].

Despite these observed increases, many women remain hesitant to receive Tdap during pregnancy due to concerns regarding safety for themselves or their babies [17], [18]. Although published data to date on the safety of maternal Tdap, including from one small clinical trial [19] and several observational studies [20], [21], [22], [23], [24], [25] have been generally reassuring, continued postmarketing surveillance of maternal Tdap vaccination is needed [26]. Goals of the current study were two-fold: (1) to provide updated estimates of Tdap coverage during pregnancy among insured women within the Vaccine Safety Datalink and (2) to evaluate risks for selected acute adverse events occurring 0–42 days following maternal Tdap vaccination.