Key takeaways:
- Concomitant influenza and pertussis vaccination at 20 weeks' gestation or later was not associated with increased risk of preterm birth (aHR, 0.83), small for gestational age (aOR, 0.87), low birth weight (aOR, 0.94), or any of six secondary maternal and neonatal outcomes.
- Outcomes were selected based on WHO and Brighton Collaboration priority frameworks for pregnancy vaccine safety, ensuring clinical and public health relevance across all assessed endpoints.
- The findings support clinicians in recommending same-day vaccination during pregnancy, with the potential to improve uptake by reducing the number of visits required to complete recommended immunizations.
Concomitant administration of influenza and pertussis vaccines during pregnancy was not associated with increased rates of preterm birth, small for gestational age, low birth weight, or any secondary adverse outcome compared with pertussis vaccination alone, according to findings from a large population-based cohort study conducted in New South Wales, Australia.1
The study retrospectively analyzed linked data from perinatal and immunization registers and hospitalization records for 13,918 matched singleton pregnancies with estimated last menstrual period between January 2021 and March 2022. Women who received both vaccines on the same day at 20 weeks' gestation or later were matched 1:1 with women who received pertussis vaccination alone, with matching on vaccination date, gestational age at vaccination, and maternal age to ensure comparability in timing and vaccine eligibility.
"The study suggests that there are no safety concerns with same-day influenza and pertussis vaccination during pregnancy with regards to the assessed pregnancy, birth, and neonatal outcomes," said study investigator Nicole Sonneveld, MSc(Med), a Senior Research Officer, National Centre for Immunisation Research and Surveillance, and PhD Candidate, University of Sydney School of Public Health.
Preterm birth occurred in 3.8% of the concomitant vaccination group and 4.4% of the matched control group (adjusted HR, 0.83; 95% CI, 0.66–1.05). Among term live births, small for gestational age infants were identified in 8.8% of the concomitant group versus 9.9% of controls (adjusted OR, 0.87; 95% CI, 0.74–1.04), and low birth weight occurred in 1.7% versus 1.6% (adjusted OR, 0.94; 95% CI, 0.66–1.35). Stillbirth occurred in 17 of the total matched cohort—fewer than 0.1%—precluding further analysis. No differences were observed between groups for any of the secondary outcomes, which included antepartum hemorrhage, postpartum hemorrhage, chorioamnionitis, preeclampsia or eclampsia, prelabor rupture of membranes, and preterm labor.
Sonneveld noted that the outcomes selected for assessment were not arbitrary.
"We selected the adverse outcomes based on those prioritized by the World Health Organization and the Brighton Collaboration for the assessment of vaccine safety during pregnancy," she said, adding that this framework ensured that each outcome was clinically meaningful by virtue of its frequency, severity, or potential public health impact.
The findings carry practical significance for antenatal care. Safety concerns remain among the most common barriers to vaccine uptake during pregnancy, and the logistical reality of prenatal visits means that same-day administration of multiple vaccines represents an important opportunity to maximize protection.
For clinicians, the results offer a clearer evidence base when counseling hesitant patients. Recommending both vaccines at a single visit is supported by this data without the caveat of unresolved safety uncertainty—a meaningful shift in how confidently providers can approach that conversation.
Reference:
1. Sonneveld N, Reekie J, Deng L, O’Grady K-A, Macartney K, Liu B. Coadministered influenza- and pertussis-containing vaccines in pregnant women. JAMA Netw Open. 2026;9(4):e267551. doi:10.1001/jamanetworkopen.2026.7551
