Key takeaways:
- The adjusted HR for preterm birth trended below 1.0 but was not statistically significant, indicating no meaningful difference between groups—a null finding that should not be interpreted as evidence of benefit from co-administration.
- The study's broad population-based design extends the safety findings to patients with high-risk medical conditions, prior adverse pregnancy outcomes, and socioeconomic disadvantage; the findings cannot be applied to multiple gestations.
- With influenza, pertussis, and RSV vaccination all now recommended in pregnancy, consolidating immunizations into fewer prenatal visits reduces appointment burden and maximizes the limited vaccination window available before delivery.
The safety evidence supporting same-day influenza and pertussis vaccination during pregnancy now extends to a broader and more clinically diverse population than previously studied—and the workflow case for co-administration deserves as much attention as the safety data, according to Nicole Sonneveld, MSc(Med), a study investigator whose findings were previously reported.1
With the core study design and primary outcome data covered in the first installment, Sonneveld, a Senior Research Officer, National Centre for Immunisation Research and Surveillance, and PhD Candidate, University of Sydney School of Public Health, addressed the nuances clinicians are most likely to encounter in practice: how to interpret a preterm birth trend that fell below 1.0, which patients the findings can and cannot be applied to, and why consolidating vaccinations matters beyond convenience.
On the preterm birth HR, Sonneveld was precise. After adjusting for socioeconomic status, smoking during pregnancy, and prior preterm birth history, the rate was numerically lower in the concomitant vaccination group—but the difference was not statistically significant.
"That suggests that overall between comparison groups there's no difference in the rate of preterm birth," she said. Clinicians should interpret the trend as a null finding, not a signal of benefit.
For patients who express hesitancy about receiving multiple vaccines at once, Sonneveld pointed to the layered reassurance the evidence base now provides. Active surveillance studies had already established that same-day administration does not increase the risk of immediate reactions such as fever. The current study adds the longer-horizon finding that there are no associated pregnancy, birth, or neonatal safety concerns.
"We really hope these findings help health care providers be more confident to recommend having the influenza and pertussis vaccines at the same time," she said, noting that a clinician recommendation remains one of the most influential drivers of patient vaccination decisions.
Sonneveld also clarified the generalizability of the findings. The population-based cohort design captured a deliberately wide cross-section of pregnant patients in New South Wales—including those with high-risk medical conditions, prior adverse pregnancy outcomes, and significant socioeconomic disadvantage.
"The only group we did not include were people pregnant with twins or higher-order multiples," she said, identifying that as the one population to which these findings cannot be directly applied.
The workflow dimension, Sonneveld argued, deserves equal emphasis. Pregnancy is a defined and time-limited vaccination window, and missed visits mean missed protection—for the pregnant patient and, through passive immunity, for the newborn.
"Same-day vaccination may help optimize vaccine uptake and reduce the total number of healthcare appointments that pregnant people require," she said, with downstream benefits to patient time, convenience, and cost. With RSV vaccination now also recommended in pregnancy, the case for maximizing each prenatal visit as a vaccination opportunity has only grown stronger.
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
