A new collaborative research led by the MRC Unit The Gambia at the London School of Hygiene &Tropical Medicine, in partnership with Radboud University Medical Center (Radboudumc), Netherlands and Charité – Universitätsmedizin Berlin, Germany, shows evidence thatvaccinating women during pregnancy strengthens their babies’ immune system in more than one way.
Following maternal vaccination against whooping cough (pertussis), antibodies were detected both in the babies’ blood and their nasal lining, the site where whooping cough bacteria – as well as other respiratory pathogens–enter the body.
Whooping cough remains a serious global health threat, causing an estimated 200,000 to 400,000 deaths each year, primarily among young infants who have not been fully vaccinated. The Gambian Pertussis study (GaPs),a phase IV randomised controlled trial conducted in The Gambia, recruited more than 300 pregnant women and their babies. Half of the women received a pertussis-containing vaccine during pregnancy, which is not part of the routine immunisation schedule in The Gambia or most of sub-Saharan Africa. After birth, babies received their routine vaccinations at 8, 12 and 16 weeks of age, including either a whole-cell pertussis vaccine (used in The Gambia) or an acellular pertussis vaccine. This allowed the team to compare how different pertussis vaccines shape babies’ immune responses, and how these responses are influenced by whether or not mothers were vaccinated against pertussis during pregnancy.
“We give the whooping cough(also known as pertussis) vaccine in pregnancy to protect babies right after birth,” explains Professor Beate Kampmann, a paediatric infectious diseases specialist and lead investigator of GaPs. “In the first weeks of life, babies are extremely vulnerable and too young to be vaccinated themselves. That’s why we vaccinate the mother during pregnancy to protect the baby passively,” she added.
Antibodies generated in the mother following vaccination are transferred across the placenta and circulate in the baby’s blood, where they are known to be protective. In addition to analysingblood samples, the team used a small, non-invasive device placed gently inside the infant’s nose to collect mucosal secretions containing key immune markers. This method enabled immune responses at the airway surface to be studied alongside those generated in the blood, offering a more complete picture of how different pertussis vaccination strategies are protective in infants.
Dr Anja Saso, a paediatrician and clinical researcher who embeddedthis immunological sub-study focusing on upper airway immune responses within the GaPs trial, highlights,“For the first time, we show that antibodies passed from mother to child after vaccination in pregnancy also reach the baby’s upper airway – the point where whooping cough bacteria enter and infection begins. This suggests maternal vaccination protects babies not only through antibodies in their blood, but potentially also directly at the airway surface, where early defense matters most.”
“Because this approach is both informative and highly reproducible, we hopeit will be used in future mother to child vaccine studies and broader research on paediatric respiratory infections, particularly in similar low-resource settings,” Dr Saso adds.
In addition to showing that the antibodies transferred from mother to baby can be found in the nasal lining, this study also demonstrates that babies who received a whole cell whooping cough vaccine developed, on average, a stronger immune response than those who received an acellular vaccine. ‘The difference is that a whole-cell vaccine contains the complete, but inactivated, whooping cough bacterium, whereas an acellular vaccine contains only a few purified components of the bacterium,’ Professor Kampmann explains. ‘Our findingsoffer further evidence – at the mucosal level – that whole-cell vaccines may support longer-term immune protection,’ adds Dr Anja Saso. ‘Acellular vaccines usually cause fewer side effects, but their protection tends to wane more quickly over time. Nevertheless, and most importantly, both types of vaccine remain highly effective at preventing severe disease, hospitalisation and death, particularly in the first year of life when infants are most at risk.’
For countries that use acellular pertussis vaccines in infancy, the GaPs trial highlights the importance of vaccination during pregnancy, which provides babies with immediate protection during the early months of life when they are most vulnerable. In settings that continue to use whole-cell vaccines for infants – mainly low- and middle-income countries – the findings support the World Health Organization’s (WHO) recommendation to maintain their use, as these vaccines may provide longer lasting immunity, including at the nasal lining where infection begins. Similar patterns were shown by the GaPs team when measuring antibody responses in the blood in the same group of infants.
The research was funded by the Innovative Medicines Initiative 2 Joint Undertaking, Horizon 2020, the European Federation of Pharmaceutical Industries and Associations, the Gates Foundation, and BactiVac.
