Pertussis Vaccination During Pregnancy Enhances Infant Immunity by Increasing and Improving Antibody Response

Recent research highlights the significant benefits of vaccinating pregnant women with the acellular pertussis vaccine. A comprehensive study conducted by the University of Turku and published in The Lancet Infectious Diseases demonstrates that maternal immunization not only elevates the quantity of pertussis-specific antibodies transferred to newborns but also enhances their functional quality. This passive immunity provides critical early-life protection against pertussis, a highly contagious respiratory disease caused by Bordetella pertussis bacteria.

In a phase 4 randomized, controlled, double-blind trial in The Gambia, researchers evaluated the immunogenicity of pertussis vaccination during pregnancy, comparing responses following administration of either acellular or whole-cell pertussis vaccines. The study confirmed that vaccinating pregnant women was safe and well tolerated, with notable boosts in the levels of pertussis-specific antibodies in infants during early life.

Pertussis has seen a worrying resurgence globally, with the World Health Organization estimating 16 million cases and approximately 195,000 deaths annually. In Europe, including Finland, dramatic increases in cases have been reported post-COVID-19 pandemic, with Finland recording the highest number since 1995 in 2024. Despite widespread vaccination programs, the disease's return underscores the importance of optimizing immunization strategies.

Currently, two types of pertussis vaccines are in use across the world: whole-cell vaccines (wPVs) and acellular vaccines (aPVs). While whole-cell vaccines are more common in low- and middle-income countries, acellular vaccines are preferred in high-income nations for primary and booster doses.

Immunization during pregnancy is strongly recommended to protect vulnerable infants who are too young to be vaccinated effectively. Maternal vaccination allows the transfer of protective antibodies across the placenta, offering infants early immunity. However, some studies have observed a phenomenon called "blunting," where maternal antibodies may reduce the infant's immune response to their initial vaccines. This effect, especially noted with IgG antibody responses to pertussis antigens, warrants further investigation, though current evidence indicates that the functional quality of antibodies and immune memory are preserved.

The Gambian study provided reassurance that maternal vaccination with diphtheria-tetanus-acellular pertussis was safe and promoted strong immune responses in infants. While some antibody responses post-vaccination show signs of blunting, the overall immune protection, including memory B-cell responses, remains intact.

Research institutes in Turku have played a key role in developing sensitive assays to measure the functional capacity of pertussis-specific antibodies. These innovative tools have been instrumental in international vaccine studies, contributing to a better understanding of how maternal immunization influences long-term childhood immunity.

Overall, the findings support the continued implementation of pertussis vaccination during pregnancy as a safe and effective strategy to protect infants from this preventable disease. Ongoing research aims to optimize vaccination timing and formulation to maximize early-life immunity while addressing the challenges of immune blunting.