Can pregnant women who are unvaccinated against Pertussis still pass antibodies to their babies?
Pregnant women who have not received the pertussis vaccine can still pass protective antibodies to their infants through the placenta. Studies indicate that babies born to unvaccinated mothers often have higher concentrations of anti-pertussis toxin antibodies at six months of age than those born to vaccinated mothers 1.
What the research says
Research comparing vaccinated and unvaccinated groups found that infants in the unvaccinated group had significantly higher anti-PT IgG concentrations at six months 1. This suggests that the lack of maternal vaccination does not prevent antibody transfer; in fact, the resulting antibody levels in these infants were robust. The study also noted that antibodies in the cord blood of both groups showed higher binding strength than what infants develop after just two vaccine doses 1.
While unvaccinated mothers pass these antibodies, the presence of high maternal antibodies can affect how the infant's own immune system responds to the first shots. Some research indicates that these maternal antibodies may blunt or interfere with the infant's subsequent immune response to the primary vaccination series 16. However, this blunting effect is primarily observed in antibody quantity and does not necessarily mean the infant lacks protection entirely, especially since unvaccinated infants still receive some passive immunity from their mothers 1.
Other studies have looked at how maternal vaccination changes the baby's innate immune responses, such as cytokine production and cell activity, which are different from the antibody transfer discussed here 7. The main takeaway is that unvaccinated mothers do pass antibodies, but the levels and the infant's future vaccine response differ from the vaccinated group 16.
What to ask your doctor
- How does the timing of my pertussis vaccination affect the amount of antibodies passed to my baby?
- What are the risks of pertussis for my baby if I am unvaccinated?
- How might my baby's response to the first vaccine shots be affected by the antibodies I pass?
- Are there other ways to protect my baby from pertussis if I cannot be vaccinated?
This question is drawn from common patient questions about OB/GYN & Women's Health and answered using cited medical research. We do not provide individualized advice.