In short
Bordetella pertussis pertactin adsorbed on aluminium phosphate is a bacterial protein used as an antigen in acellular pertussis vaccines. It is one of several components included in combination vaccines designed to protect against whooping cough. One completed Phase 3 clinical trial (NCT05856396) investigated how maternal vaccination during pregnancy affects antibody transfer to infants, enrolling 240 participants.
Key points
- Bordetella pertussis pertactin is a surface protein from the bacterium that causes whooping cough.
- It is included as an antigen in acellular pertussis vaccines, often combined with other vaccine components.
- One Phase 3 trial (NCT05856396) studied maternal vaccination and antibody transfer to newborns.
- The trial enrolled 240 pregnant women and has been completed.
- Researchers measured the magnitude of antibody responses to pertussis vaccination in mothers and infants.
- Some circulating Bordetella pertussis strains have lost the pertactin protein, raising questions about vaccine-driven evolution.
What is Bordetella pertussis pertactin?
Bordetella pertussis pertactin adsorbed on aluminium phosphate is a protein derived from the outer membrane of Bordetella pertussis, the bacterium that causes whooping cough (pertussis). Pertactin is one of several immunogens—substances that trigger an immune response—used in acellular pertussis vaccines. These vaccines contain purified components of the bacterium rather than whole inactivated cells. Pertactin is classified as a bacterial outer membrane protein and is included in most acellular pertussis vaccines used in the United States, typically alongside pertussis toxin, filamentous hemagglutinin, and sometimes fimbrial proteins.
How does Bordetella pertussis pertactin work?
Pertactin is believed to help the bacterium bind to respiratory epithelial cells—the cells lining the airways—and to resist clearance by neutrophils, which are white blood cells that fight infection. These properties may affect how easily the bacterium spreads and how severe the disease becomes. When pertactin is included in a vaccine, the immune system learns to recognise this protein and produces antibodies against it. These antibodies can then help protect against future infection. However, the emergence of pertactin-deficient strains of Bordetella pertussis in highly vaccinated populations has raised questions about whether vaccine-driven evolution is occurring.
Which conditions is it used or studied for?
- Whooping cough (pertussis) — a highly contagious respiratory infection caused by Bordetella pertussis. Pertactin is used as a vaccine antigen to help prevent this disease, and its role in maternal vaccination during pregnancy is being studied.
How is Bordetella pertussis pertactin given?
Pertactin is not given as a standalone product. It is administered as one component of combination vaccines given by intramuscular injection. In the registered clinical trial, the vaccines studied were Vaxelis (a hexavalent vaccine containing diphtheria, tetanus, pertussis, hepatitis B, poliomyelitis, and Haemophilus type b components) and Triaxis (a trivalent vaccine containing diphtheria, tetanus, and pertussis components). Both vaccines contain pertactin as part of their acellular pertussis component.
What do the clinical trials show?
One completed Phase 3 clinical trial (NCT05856396), titled "Maternal determinants of infant immunity to pertussis (MADI-02)", investigated how maternal immunisation during pregnancy affects antibody responses in infants. The trial enrolled 240 participants and focused on pregnant women who received pertussis-containing vaccines. The primary outcome measured was the magnitude of antibody responses to pertussis vaccination—specifically, how much antibody is produced in response to the vaccine, how well maternal antibodies transfer to the newborn, and how infants respond to their own vaccination. The study has been completed, though the published results are not yet available in the registry record.
What side effects are known?
The supplementary sources provided do not contain specific information about side effects associated with pertactin as an individual vaccine component. Side effects of combination vaccines containing pertactin are described in the product information for each vaccine and generally include local reactions at the injection site and systemic reactions such as fever. However, no side effect data specific to pertactin alone are available in the provided sources.