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Pertussis filamentous haemagglutinin adsorbed on aluminium hydroxide, hydrated is a protein antigen derived from Bordetella pertussis, the bacterium responsible for whooping cough (pertussis). It is not used as a medicine on its own but is one of several components in authorised combination vaccines such as Infanrix hexa, Hexyon and Boostrix. These vaccines are authorised as medicines in the European Union, with authorisation records including EU/1/00/152/001 and EU/1/13/829/002.[2]
Pertussis filamentous haemagglutinin (FHA) is a surface protein of Bordetella pertussis that helps the bacterium attach to cells in the respiratory tract. In acellular pertussis vaccines, FHA is one of the purified antigens presented to the immune system, along with pertussis toxoid and, in some products, pertactin. The World Health Organization product information for Boostrix lists FHA at a content of 8 micrograms per 0.5 ml dose, adsorbed on aluminium hydroxide.[7]
In the registry records provided, FHA is part of fixed combination products including Infanrix hexa, Hexyon and Tetravac. It appears as an auxiliary intervention in 3 trials, as a test product in 1 trial, and as a placebo in 1 trial.[2]
FHA works as a vaccine antigen: when injected, it trains the immune system to recognise the real bacterium. A study in mice showed that intranasal immunisation with FHA combined with recombinant pertussis toxin induced both systemic antibody responses (serum IgG) and mucosal responses (secretory IgA in lung lavage and nasal washes). The mucosal response was considerably higher when chitosan was used as a delivery system compared to FHA and pertussis toxin alone.[8] In licensed vaccines, FHA is adsorbed onto aluminium hydroxide, which acts as an adjuvant to strengthen the immune response.[7]
FHA is administered as part of a combination vaccine in the form of a suspension for injection, given by intramuscular injection. The product information for Boostrix specifies deep intramuscular injection, preferably into the deltoid muscle of the upper arm, with a single 0.5 ml dose for booster vaccination.[7] In the trial records, the route is listed as intramuscular use or intramuscular injection; one record also lists intravenous use, which reflects the range of products in the combination records rather than the FHA component itself.[2]
The six registry records are not trials of FHA itself; they are studies in which FHA-containing combination vaccines appear as auxiliary or comparator products. The trials investigate other investigational products, including pentavalent meningococcal vaccines, a maternal pertussis immunisation schedule, a treatment for generalised myasthenia gravis, a gene therapy for X-linked hyper-IgM syndrome, and a complement inhibitor for kidney disease. FHA-containing vaccines are used to provide standard vaccination cover or as comparator vaccines within these study designs.
The trials range from Phase 1 to Phase 3. The largest is a Phase 2 study of an investigational pentavalent meningococcal ABCYW vaccine with 750 participants, in which Infanrix hexa and Hexyon serve as comparator vaccines.[1] A Phase 3 study of maternal pertussis immunisation in Finland enrolled 138 participants and measured pertussis toxin-specific IgG antibody concentrations in children at four years of age.[2]
| Trial identifier | Phase | Condition | Status | Participants |
|---|---|---|---|---|
| NCT05082285[5] | Phase 1 | Meningococcal infections | Completed | 703 |
| 2023-510465-10-00[1] | Phase 2 | Meningococcal immunisation | Authorised | 750 |
| 2024-510787-23-00[2] | Phase 3 | Pertussis | Completed | 138 |
| 2025-522406-20-00[3] | Phase 1 | Generalised and ocular myasthenia gravis | Authorised | 135 |
| 2025-524635-39-00[4] | Phase 1/2 | X-linked hyper-IgM syndrome type 1 | Authorised | 6 |
| NCT06989359[6] | Phase 2 | Complement-mediated kidney disease | Authorised | 45 |
The WHO product information for Boostrix does not list side effects in the excerpt provided, but it notes that the vaccine may contain traces of formaldehyde used during manufacturing and advises against administration if foreign particulate matter or a change in physical appearance is observed.[7] The trial records describe monitoring for solicited administration site and systemic events during the 7 days after vaccination, unsolicited adverse events, medically attended adverse events, serious adverse events, and adverse events of special interest.[5]
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