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Pertussis pertactin is a protein found on the surface of the bacterium Bordetella pertussis, which causes whooping cough. It is one of several antigens included in acellular pertussis vaccines, which are made from purified components of the bacterium rather than whole killed cells. The full registry name lists it together with other pertussis antigens: pertussis toxoid, pertussis filamentous haemagglutinin, pertussis pertactin, and pertussis fimbrial agglutinogens (FIM) 2 and 3.[2]
Pertussis pertactin is not a medicine on its own. It is a component of combination vaccines that also protect against diphtheria and tetanus, and in some products against poliomyelitis as well.
Pertactin is also the subject of scientific attention because some circulating strains of Bordetella pertussis have lost the pertactin protein. A 2024 review discusses the epidemiology of pertactin-deficient strains and their implications for surveillance and public health.[6]
Pertussis pertactin acts as an antigen: a substance that the immune system recognises as foreign and responds to. When a vaccine containing pertactin is injected, the immune system produces antibodies against it. These antibodies help the body recognise and fight Bordetella pertussis if the person is later exposed to the bacterium.[5]
The trials listed in the registry measure immune responses to pertussis vaccination by looking at antibody levels in the blood. For example, one trial measured the percentage of participants with pertussis toxin-specific IgG antibody geometric mean concentration (GMC) of at least 5 IU/mL before vaccination.[2] Another trial measured the magnitude of antibody responses to pertussis vaccination in infants born to mothers immunised during pregnancy.[3]
Public health sources note that protection against pertussis after either natural infection or vaccination is not long-lasting, which is why booster doses are used in adolescents and adults.[5]
Vaccines containing pertussis pertactin are used to protect against whooping cough (pertussis), a respiratory tract illness caused by Bordetella pertussis bacteria. The same combination vaccines also protect against diphtheria and tetanus, and some also against poliomyelitis.[5]
Pertussis pertactin is given as part of a suspension for injection, administered by intramuscular injection. In the trials, the vaccines were given as a 0.5 mL dose, and in one trial the dose volume was recorded as 1 mL.[4] The product names in the registry include Triaxis (a diphtheria, tetanus and acellular pertussis vaccine with reduced antigen content) and REPEVAX (a diphtheria, tetanus, acellular pertussis and inactivated poliomyelitis vaccine).[2][1]
Four Phase 3 trials in the EU registry studied vaccines containing pertussis pertactin. All four are interventional studies, and their status is completed or authorised. The largest trial enrolled 240 participants and the smallest enrolled 96.[2][4]
Two trials focused on whooping cough immunity in adults: one in healthcare workers receiving a dTap booster, and one in healthy adults exposed to Bordetella pertussis in a controlled human infection model.[2][1] Two trials studied vaccination during pregnancy and the transfer of maternal antibodies to infants.[3][4]
The trials measured different aspects of immune response. The healthcare worker trial measured the percentage of participants with pertussis toxin-specific IgG antibody levels of at least 5 IU/mL before vaccination.[2] The human challenge trial measured the rate of Bordetella pertussis colonisation, defined as any positive culture from nasal wash samples between Day 3 and Day 28 after challenge.[1] The maternal immunity trials measured the magnitude of antibody responses to pertussis vaccination in infants, and antibody levels and functional characteristics in maternal blood at baseline, after vaccination, at delivery, and 6 months postpartum.[3][4]
The trials enrolled different populations: 100 healthcare workers in the booster vaccination trial, 99 healthy adults in the human challenge trial, 240 participants in the maternal determinants of infant immunity trial, and 96 pregnant women in the timing of vaccination trial.[1]–[4]
The supplementary sources provided do not include a specific list of side effects for pertussis pertactin. The public summary from the Danish Medicines Agency focuses on disease epidemiology rather than adverse reactions.[5] No side effect data from the supplementary sources is available to report here.
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