For newborns, the world can be a dangerous place. One cough, one exposure, one invisible bacterium can be life-threatening in the earliest weeks of life, especially when the baby is still too young to be vaccinated.

New research offers reassuring evidence that protection can begin even before birth, thanks to a simple vaccine given during pregnancy.

In the first weeks of life, babies are extremely vulnerable and too young to be vaccinated themselves. The study underscores how life-saving maternal vaccination during pregnancy can be.

An international study, led by researchers at Radboud University Medical Center in the Netherlands, shows that vaccinating pregnant women against whooping cough (pertussis) not only transfers protective antibodies to their babies' bloodstreams, but delivers those antibodies directly to the nasal mucosa — the very place where the dangerous bacteria first enter the body.

That kind of frontline immune protection had not been clearly demonstrated — until now.

Pregnant women in the Netherlands have routinely been offered what's known as the “22-week shot”, a pertussis vaccination designed to protect babies immediately after birth since 2019. That's because in the first weeks of life, babies are extremely vulnerable and too young to be vaccinated themselves.

Antibodies formed in the mother cross the placenta and enter the baby's circulation before birth. What makes this study novel, and particularly important, is where those antibodies end up. The researchers found them not only in the infants' blood, but also in their nasal passages, the primary entry point for Bordetella pertussis, the bacterium that causes whooping cough.

To reach these conclusions, the team studied 343 mothers and their babies in a collaboration between Radboud University Medical Center and the university's Medical Research Council Unit The Gambia. About half of the pregnant women received the whooping cough vaccine during pregnancy. After birth, researchers measured immune responses in the infants.

Mothers who had been vaccinated during pregnancy passed on antibodies through the placenta that were subsequently detected in the baby's nasal mucosa.

The findings matter far beyond Europe. Whooping cough is generally well controlled in high-income countries, but it remains deadly in many parts of the world. Each year, an estimated 200,000 to 300,000 people die from whooping cough, most of them young infants living in low- and middle-income countries where access to vaccines is often limited.

The study also explored the way different types of childhood vaccines shape immune response. Babies, who later received the whole-cell whooping cough vaccine at 8, 12 and 16 weeks of age, developed, on average, a stronger immune response than those who received the newer acellular vaccine commonly used in Europe and other high-income countries.

Vaccinating pregnant women against whooping cough not only transfers protective antibodies to their babies' bloodstreams, it also delivers those antibodies to the very place where the bacteria first enter the body.

“Acellular vaccines usually cause fewer side effects but often also provide shorter-lasting protection. Our findings suggest that whole-cell vaccines may support longer-term immune protection,” the co-author of the study, Janeri Fröberg, a postdoctoral researcher at Radboud University Medical Center, said in a press release.

These results help explain why the World Health Organization (WHO) continues to recommend the use of whole-cell vaccines in many settings. For countries that already use them, the findings support maintaining that approach. For lower-income countries, where most pertussis deaths occur, the study underscores how life-saving maternal vaccination during pregnancy can be.

For expectant parents, the message is clear: the 22-week shot doesn't just boost immunity — it positions it exactly where babies need it most, exactly when they need it most.

The study is published in The Lancet Infectious Diseases.