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Completed

NCT Number: NCT07735767

Tdap Vaccination During Pregnancy or Postpartum and Lactation-Related Outcomes

A retrospective cohort study based on the secondary use of pre-existing data. The study assesses the association between antenatal and postpartum maternal Tdap vaccination and select infant and lactation-related outcomes.

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Key information

Conditions

Pertussis Vaccines Behavior Breast Feeding Feeding Behavior

Age range

16 year–49 year

Sex eligibility

Female

Study type

Observational

About this study

Since 2012, the United States Advisory Committee on Immunization Practices has recommended administering the Tdap (tetanus, diphtheria, acellular pertussis) vaccine during every pregnancy, ideally between 27 and 36 gestational weeks, to reduce pertussis morbidity and mortality in young infants. Although the safety of Tdap during pregnancy for maternal and birth outcomes is well-documented, there are very limited data on lactation-related outcomes following Tdap vaccination.

This is a novel study of antenatal and postpartum Tdap vaccination and select adverse infant and lactation-related outcomes in mother-infant pairs to address the need for comprehensive safety data. Study specific aims:

Aim 1: To assess associations between receipt of Tdap vaccine in pregnancy and the risk of adverse infant and lactation-related outcomes.

Aim 2: To assess associations between receipt of Tdap vaccine postpartum and the risk of adverse infant and lactation-related outcomes among women who are breastfeeding in the 3 months postpartum.

No investigational vaccines will be administered in this study. Participants will be included in the study on the basis of their having received Tdap vaccine as part of routine care.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

The study includes pregnant women aged 16-49 years at delivery who had a live-birth delivery between 01 January 2014 (01 June 2018 for one site given data availability) and 31 December 2022, received prenatal care within the participating health systems before 6 months gestation, had a gestational age at delivery of at least 27 weeks, and linked to an infant with a WCV before 2 months of age within the participating health systems.

Exclusion criteria

We excluded those with Tdap vaccination before the recommended gestational age of 27 gestational weeks. For postpartum analyses, we excluded those who did not initiate human milk feeding or where human milk feeding information was not available.

Treatment and study plan

Tetanus Toxoid, acellular pertussis, diphtheria toxoid

Biological

No investigational vaccines will be administered in this study. Participants will be included in the study on the basis of their having received Tdap vaccine as part of routine care.

Primary outcomes

  1. Infant growth - failure to thrive (Subgroup Pregnancy)

    Time frame: 3 months (91 days) to 12 months of age

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy and up to 90 days after delivery

  2. Infant growth - failure to thrive (Subgroup Postpartum)

    Time frame: 3 months (91 days) to 12 months of age

    Among patients who did not discontinue human milk feeding on or before 90 days after delivery.

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

  3. Infant health care utilization - Number of infant outpatient visits up to 6 months of age (Subgroup Pregnancy)

    Time frame: 0 to 6 months after delivery

    Count of unique dates of outpatient visits in the 6 months after delivery.

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy and up to 90 days after delivery

  4. Infant health care utilization - Number of infant outpatient visits in the 90 days after index date (Subgroup Postpartum )

    Time frame: up to 6 months: 90-day window for vaccination plus 90-day window for outcome assessment

    Among patients who did not discontinue human milk feeding before index date (ie, vaccination or pseudovaccination date), count of unique dates of outpatient visits in the 90 days after vaccination or pseudovaccination.

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

  5. Infant health care utilization - Number of infant emergency department visits up to 6 months of age (Subgroup Pregnancy)

    Time frame: 0 to 6 months after delivery

    Count of unique dates of emergency department visits in the 6 months after delivery.

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy and up to 90 days after delivery

  6. Infant health care utilization - Number of infant emergency department visits in 90 days after index date (Subgroup Postpartum)

    Time frame: Up to 6 months: 90-day window for vaccination plus 90-day window for outcome assessment.

    Among patients who did not discontinue human milk feeding before index date (ie, vaccination or pseudovaccination date), count of unique dates of emergency department visits in the 90 days after vaccination or pseudovaccination.

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

  7. Human milk feeding initiation vs no initiation (Subgroup Pregnancy)

    Time frame: 0 to 12 months

    Any or exclusive human milk versus formula only or no human milk feeding documented during follow up.

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy

  8. Any human milk feeding vs none around the 2-month Well Child Visit (WCV) (Subgroup Pregnancy)

    Time frame: 42 to 104 days after delivery

    Any human milk versus formula only or no human milk feeding documented 42 to 104 days after delivery

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy through 41 days after delivery

  9. Any human milk feeding vs none around the 2-month WCV (Subgroup Postpartum)

    Time frame: 42 to 104 days after delivery

    Among those patients who did not discontinue human milk feeding before Tdap vaccine receipt or before the outcome window of interest, any human milk versus formula only or no human milk feeding documented 42 to 104 days after delivery

    Exposure: Any Tdap 0 to 41 days after delivery

    Comparator: No Tdap during pregnancy through 41 days after delivery

  10. Exclusive human milk feeding vs none around the 2-month WCV (Subgroup Pregnancy)

    Time frame: 42 to 104 days after delivery

    Exclusive human milk feeding only versus formula, with or without human milk documented 42 to 104 days after delivery

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy through 41 days after delivery

  11. Exclusive human milk feeding vs none around the 2-month WCV (Subgroup Postpartum)

    Time frame: 42 to 104 days after delivery

    Among those patients who did not discontinue human milk feeding before Tdap vaccine receipt or before the outcome window of interest, exclusive human milk feeding only versus formula, with or without human milk documented 42 to 104 days after delivery

    Exposure: Any Tdap 0 to 41 days after delivery Comparator: No Tdap during pregnancy through 41 days after delivery

  12. Any human milk feeding vs none around the 6-month WCV (Subgroup Pregnancy)

    Time frame: 148 to 210 days after delivery

    Any human milk versus formula only or no human milk feeding documented 148 to 210 days after delivery

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy through 147 days after delivery

  13. Any human milk feeding vs none around the 6-month WCV (Subgroup Postpartum)

    Time frame: 148 to 210 days after delivery

    Among those patients who did not discontinue human milk feeding before Tdap vaccine receipt or before the outcome window of interest, any human milk versus formula only or no human milk feeding documented 148 to 210 days after delivery

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

  14. Exclusive human milk feeding vs none around the 6-month WCV (Subgroup Pregnancy)

    Time frame: 148 to 210 days after delivery

    Exclusive human milk feeding only versus formula, with or without human milk documented 148 to 210 days after delivery

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy through 147 days after delivery

  15. Exclusive human milk feeding vs none around the 6-month WCV (Subgroup Postpartum)

    Time frame: 148 to 210 days after delivery

    Among those patients who did not discontinue human milk feeding before Tdap vaccine receipt or before the outcome window of interest, exclusive human milk feeding only versus formula, with or without human milk documented 148 to 210 days after delivery

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

Secondary outcomes

  1. Infant growth - Rate of weight gain (Subgroup Pregnancy)

    Time frame: 3 - 9 months (To determine predicted values at 9 months of age, measurements up to 12 months were used)

    Average predicted rate of weight gained (kg/month) between 3 and 9 months < 5th percentile for sex in the study population vs ≥ 5th percentile

    Exposure: Tdap on or after 27 gestational weeks (ie, > 188 days gestation) and less than delivery date

    Comparator: No Tdap during pregnancy and up to 90 days after delivery

  2. Infant growth - Rate of weight gain (Subgroup Postpartum)

    Time frame: 3 - 9 months (To determine predicted values at 9 months of age, measurements up to 12 months were used)

    Among those patients who not discontinue human milk feeding on or before 90 days after delivery, average predicted rate of weight gained (kg/month) between 3 and 9 months < 5th percentile for sex in the study population vs ≥ 5th percentile

    Exposure: Any Tdap 0 to 90 days after delivery

    Comparator: No Tdap 0 to 90 days after delivery

Sponsors and collaborators

Lead sponsor

HealthPartners Institute

Other

Collaborators

  • Kaiser Permanente
  • Sanofi

Registry information

Important dates

Study start
2014
Primary completion
2022
Study completion
2022
First posted
Jul 30, 2026
Registry last updated
Jul 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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