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. Author manuscript; available in PMC: 2026 Aug 4.
Published in final edited form as: Prev Med. 2014 Jun 18;67:316–319. doi: 10.1016/j.ypmed.2014.05.025

Receipt of pertussis vaccine during pregnancy across 7 Vaccine Safety Datalink Sites

Elyse O Kharbanda 1, Gabriela Vazquez-Benitez 1, Heather Lipkind 2, Allison L Naleway 3, Nicola P Klein 4, T Craig Cheetham 5, Simon J Hambidge 6, Claudia Vellozzi 7, James D Nordin 1
PMCID: PMC13431813  NIHMSID: NIHMS2199756  PMID: 24952094

Abstract

Objective:

In response to widespread pertussis outbreaks and infant deaths, in 2010, the California Department of Health (CDPH) and in 2011 the Advisory Committee on Immunization Practices (ACIP) advised that the tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine be administered during pregnancy. Goals of this study were to describe Tdap coverage among pregnant women following these recommendations.

Methods:

In this observational cohort study, we utilized electronic medical record and claims data from seven Vaccine Safety Datalink sites to identify pregnancies and Tdap administrations. All Tdap doses were classified as pre-pregnancy, during pregnancy or post-pregnancy/postpartum. For pregnancies ending in a live birth, we evaluated factors associated with Tdap vaccination.

Results:

Among 289,141 live births at the California VSD sites, receipt of Tdap during pregnancy increased substantially in the years 2010, 2011, and 2012, when coverage was 15.9, 30.0 and 19.5%, respectively. Among 82,398 women with live births at the Oregon, Washington, Colorado, Wisconsin and Minnesota VSD sites, receipt of Tdap during pregnancy first increased in 2012, at 16.0%. Women receiving early prenatal care and other vaccine(s) during pregnancy had higher Tdap coverage.

Conclusion:

We observed substantial increases in Tdap coverage during pregnancy following CDPH and ACIP recommendations.

Keywords: Pertussis, pregnancy, vaccine coverage

INTRODUCTION

Bordetella pertussis is a highly contagious bacterium that infects the human respiratory tract. While most pertussis infections in children and adults are asymptomatic or result in mild illness, infants with pertussis can experience apnea, respiratory failure, neurologic complications, and death.1

Two tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines were licensed in the United States in 2005 for routine use in non-pregnant adolescents and adults.2,3 While starting in 2006 the American Academy of Pediatrics endorsed the use of Tdap for pregnant adolescents4, more often cocooning or vaccinating parents and other close contacts was recommended to prevent pertussis transmission and severe illness in newborns.3,5 In 2010, in response to a statewide pertussis outbreak with infant deaths,6,7 the California Department of Health (CDPH) advised that Tdap be administered to previously unvaccinated pregnant women.8 In 2011, the Advisory Committee on Immunization Practices (ACIP) followed with similar recommendations for pregnant women across the United States. In 2012, ACIP further revised recommendations that Tdap be administered to all pregnant women during every pregnancy, even if previously vaccinated.9 To date there is limited data on receipt of Tdap during pregnancy. The aim of this report was to describe Tdap coverage for pregnancies occurring from 2007–2102 at seven geographically diverse integrated health care systems within the Vaccine Safety Datalink (VSD).

MATERIALS AND METHODS

The VSD is a collaborative effort between the Center for Disease Control and Prevention’s Immunization Safety Office and 9 large medical care organizations in the U.S. and includes data on approximately 2.5 million women of reproductive age.10 For this report, data on Tdap coverage was available from seven VSD sites: Group Health Cooperative (WA), Kaiser Permanente Northwest (OR) and (WA), Kaiser Permanente Northern California (CA), Southern California Kaiser Permanente (CA), HealthPartners (MN), Marshfield Clinic (WI), and Kaiser Permanente Colorado (CO).

Pregnancies ending between 1/1/2007–11/15/2012 were identified using a validated algorithm.11 The algorithm utilizes claims, administrative, and birth data to a) identify pregnancies, b) determine pregnancy outcomes and c) estimate gestational age at pregnancy outcome.11 This algorithm has been used in prior studies of vaccine safety12,13 and vaccine coverage during pregnancy.14

To be included in this report, pregnant women 14–49 years of age were required to have continuous insurance coverage from 6 months prior to pregnancy through 6 weeks after pregnancy end with no more than a 30-day gap. Women with ectopic pregnancies, gestational trophoblastic disease, and pregnancies whose outcome could not be determined with available data were excluded. Women with live births and no medical visits recorded throughout pregnancy were also excluded.

Identification of Tdap administrations

Receipt of Tdap from 1/1/2005–12/31/2012 was identified from electronic medical record and claims data. All Tdap doses were then classified as: Pre-pregnancy (1/1/2005 through 7 days after the last menstrual period (LMP); During pregnancy (8 days after LMP through 7 days before pregnancy end); Post-pregnancy/Postpartum (6 days before pregnancy end through 42 days after pregnancy end). Categories were assigned to avoid pre-pregnancy and postpartum vaccines being misclassified as occurring during pregnancy.15

Analysis

For pregnancies in the cohort, we report the proportion receiving Tdap pre-pregnancy, during pregnancy, and post-pregnancy/postpartum. We then describe Tdap coverage by pregnancy outcome, year, age, and socioeconomic status. Among pregnancies ending in a live birth, we evaluated Tdap coverage by year, age, socio-demographic factors, health care utilization and pregnancy risk, stratified by California versus other VSD sites. All data were analyzed using SAS/STAT software, Version 9.3 (SAS Institute Inc). This study was approved by the Institutional Review Boards at all participating sites and the Centers for Disease Control and Prevention.

RESULTS

Of 535,851 pregnancies at seven VSD sites over six years with continuous insurance enrollment, we excluded 15,157 (2.8%) based on pregnancy outcome and 2,994 (0.6%) for having no medical claims throughout pregnancy. The final study cohort included 517,700 pregnancies with end dates between 1/1/07–11/15/2012. Pregnancy outcomes were: live birth (71.7%), spontaneous abortion (14.8%), therapeutic abortion (13.0%) and stillbirth (0.4%).

Across all pregnancies, 25.3% received Tdap before pregnancy, 7.1% during pregnancy and 10.8% within six weeks of pregnancy end. Receipt of Tdap during pregnancy increased steadily in 2010 and 2011 but then decreased in 2012. (Table 1)

Table 1.

Receipt of Tdap among all pregnancies in cohort*

N Pre-pregnancy (%) Pregnancy (%) Postpartumd (%) Did not receive Tdap (%)
Pregnancy outcome
 Live birth 371,539 23.5 9.5 14.4 53.8
 SAB, SB or TABa 146,161 30.0 1.2 1.6 67.2
Year
 2007 84,278 3.2 0.5 2.3 94.0
 2008 84,827 8.6 0.7 6.4 84.5
 2009 84,581 16.8 1.0 13.4 69.3
 2010 89,888 26.5 9.2 18.9 47.0
 2011 91,445 40.1 17.1 14.2 30.1
 2012 82,681 56.1 13.7 8.8 22.6
Site
 California VSD sites 407,239 23.6 8.3 10.7 58.2
 Other VSD sitesb 110,461 31.5 3.0 11.2 55.2
Maternal age
 <18 12,488 46.6 4.3 5.7 45.7
 18–24 90,069 28.4 6.0 8.5 58.3
 25–34 286,516 23.7 7.8 11.8 57.5
 ≥35 128,627 24.8 6.8 10.6 58.4
Socioeconomic statusc
 Medium/High 314,364 26.2 7.4 13.0 54.3
 Low 142,354 23.2 9.3 9.9 58.7
 Missing 60,982 25.8 1.1 1.5 71.7
TOTAL, All pregnancies 517,700 25.3 7.1 10.8 57.6
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a

SAB=Spontaneous abortion, SB=Stillbirth, TAB=Therapeutic abortion

b

Other VSD sites located in: Colorado, Minnesota, Oregon, Washington and Wisconsin

c

Low socioeconomic status defined as living in data census tract having 20% or more of the population living at less than 150% of the federal poverty level

d

Within 42 days of end of pregnancy/postpartum for live births

*

Row percents may add to >100 as women may have received Tdap in more than one period (eg, pre-pregnancy and postpartum)

Of 289,141 pregnancies from the CA VSD sites with a live birth, receipt of Tdap during pregnancy increased markedly from 0.3% in 2007 to 30.4% in 2011 but decreased to 19.5% in 2012. Pre-pregnancy receipt of Tdap increased steadily each year, by 2011 35.3% and by 2012 53.8% of women with live births in CA had received Tdap prior to pregnancy. In 2011, 15.9% of pregnancies did not receive Tdap in any period (pre-pregnancy, during pregnancy or postpartum); this decreased to 14.6% in 2012. Among those vaccinated during pregnancy, receipt of Tdap at ≥20 weeks gestation increased from 12.3% in 2007 to 69.4% in 2012.

Of 82,398 pregnancies occurring in the WA, OR, MN, WI and CO VSD sites and ending in a live birth, receipt of Tdap during pregnancy increased from 0.8% of pregnancies in 2007 to 16.1% in 2012. Pre-pregnancy and postpartum Tdap administration also increased substantially over time. The proportion who did not receive Tdap in any period decreased consistently from 87.3% in 2007 to 17.4% in 2012. Among those vaccinated during pregnancy, receipt of Tdap at ≥20 weeks gestation increased from 16.7% in 2007 to 91.7% in 2012.

Tdap coverage among live births, by sociodemographc, healthcare utilization and pregnancy risk is shown in Table 2.

Table 2.

Receipt of Tdap during pregnancy, live births in California Vaccine Safety Datalink (VSD) sites and Other VSD Sitesa

Received Tdap During Pregnancy
California VSD sites Other VSD Sitesa
Number of pregnancies N (%) vaccinated Number of pregnancies N (%) vaccinated
Year
 2007 48,398 155 (0.3) 13,488 108 (0.8)
 2008 48,828 214 (0.4) 14,161 171 (1.2)
 2009 48,434 410 (0.8) 13,965 192 (1.4)
 2010 48,321 7,672 (15.9) 14,089 219 (1.6)
 2011 49,227 14,765 (30.0) 14,229 318 (2.2)
 2012 45,933 8,946 (19.5) 12,466 2,000 (16.0)
Maternal Age
 <18 years 5,647 419 (7.4) 1,238 29 (2.3)
 18–24 43,903 4,546 (10.4) 11,980 473 (3.9)
 25–34 171,095 19,615 (11.5) 51,381 1,849 (3.6)
 ≥35 years 68,496 7,582 (11.1) 17,799 657 (3.7)
Socioeconomic statusb
 Medium/High 186,821 19,926 (10.7) 69,406 2,472 (3.6)
 Low 102,283 12,232 (12.0) 12,962 536 (4.1)
 Missing 37 - 30 -
Prenatal care index
 Adequate/Plus 223,015 26,770 (12.0) 42,485 1,598 (3.8)
 Intermediate 56,227 4,635 (8.2) 23,862 952 (4.0)
 Inadequate 9,780 749 (7.7) 16,003 458 (2.9)
 Missing 119 - 48 -
Care in 1st trimester
 Yes 273,121 30,802 (11.3) 68,883 2,605 (3.8)
 No 15,316 1,339 (8.7) 6,999 185 (2.6)
 Missing 704 21 (3.0) 6,516 218 (3.3)
Delivery <37 weeks
 Yes 23,196 1,981 (8.5) 5,991 165 (2.8)
  No 265,945 30,181 (11.3) 76,407 2,843 (3.7)
Pregnancy risk
 Comorbiditiesc 51,672 5,440 (10.5) 13,012 488 (3.8)
 No comorbidities 237,469 26,722 (11.3) 69,386 2,520 (3.6)
 Complicationsd 84,581 9,771 (11.6) 23,094 842 (3.6)
 No complications 204,560 22,391 (10.9) 59,304 2,166 (3.7)
Other vaccine in pregnancye
 Yes 113,516 20,543 (18.1) 38,442 1,778 (4.6)
 No 175,625 11,619 (6.6) 43,956 1,230 (2.8)
TOTAL 289,141 32,162 (11.1) 82,398 3,008 (3.7)
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a

Other VSD sites located in: Colorado, Minnesota, Oregon, Washington and Wisconsin

b

Low socioeconomic status defined as living in a census tract having 20% or more of the population living at less than 150% of the federal poverty level

c

Comorbidities included pulmonary disease, hypertension or other heart disease, diabetes, renal or neurologic conditions diagnosed from 6 month prior to last menstrual period through end of pregnancy

d

Pregnancy complications included gestational diabetes, gestational hypertension and hemorrhage in early pregnancy

e

Other vaccines included: inactivated influenza vaccines (95.9%), Hepatitis A/Hepatitis B (1.4%), Human Papillomavirus Vaccine (1.1%), Other (1.6%)

DISCUSSION

Administering Tdap during the third trimester of pregnancy is likely to be the most effective strategy for preventing severe pertussis infections in newborns9,16,17 and thus the CDPH and ACIP recommendation have been broadly endorsed.18 In this study, we observed a marked response to recommendations to administer Tdap during pregnancy to women not previously vaccinated across seven geographically diverse integrated health delivery systems.

At the CA VSD sites, increases in Tdap coverage during pregnancy began in 2010, following the CDPH recommendations; at the other VSD sites, increases were first observed in 2012, following the 2011 ACIP recommendations. The decline in Tdap coverage during pregnancy in CA in 2012 was likely because more than half of women that year had received Tdap prior to pregnancy. Thus, based on recommendations at the time, these women were not eligible to receive another Tdap dose.

We observed larger increases in receipt of Tdap among women receiving adequate prenatal care, those with medical care in their first trimester, and among full term births. These associations likely represent pregnancies with more contact with prenatal providers and thus increased opportunities to vaccinate.

Tdap is now the second vaccine, following influenza, specifically recommended for routine use during pregnancy. For influenza, providers and women were initially hesitant regarding vaccination during pregnancy.19 However, since the H1N1 influenza pandemic, where pregnant women were disproportionately affected, vaccine uptake has increased remarkably.20 Similarly, the marked increase in Tdap administration during pregnancy at the CA sites in 2010 may have reflected fears related to the ongoing pertussis outbreak.7

Several limitations to this report should be noted. First, the data presented are novel but do not reflect the current ACIP recommendations. Second, our sample is limited to women with continuous insurance enrollment receiving care within large integrated health care systems. Women who were uninsured prior to becoming pregnant and those with fragmented care may be less likely to receive Tdap. In addition, Tdap administration outside the healthcare system or administration of Tdap that did not generate a medical claim may have been missed. Furthermore, for women who did not receive Tdap during pregnancy, details regarding whether the vaccine was offered during routine prenatal care were not available.

Previously, our team reported on vaccines administered to pregnant women within the VSD from 2007 through 2009.14 The current report expands on this work by including pregnancies from 2010 through 2012, highlighting the response to the 2010 CDPH and 2011 ACIP recommendations.

Acknowledgements

Findings of this study represent those of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.

This study was funded by the Centers for Disease Control and Prevention, Contract 200-2012-53526. Dr. Claudia Vellozzi is employed by the funder and a collaborator on this research. Dr. Vellozzi assisted with study design, interpretation of findings and the decision to submit this article for publication. This paper did undergo the CDC clearance process.

Conflicts of interest

Dr. Nicola Klein receives research support from GlaxoSmithKline, Sanofi Pasteur, Novartis, Pfizer and Merck. Dr. Allison Naleway receives research support from GlaxoSmithKline. Dr. Cheetham receives research support from Merck. The remaining co-authors have no financial conflicts of interest to report.

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