Efficacy of five H5N1 vaccines in fattening geese
A study published in Vaccines evaluates the safety, immunogenicity, and efficacy of five commercial vaccines against highly pathogenic avian influenza virus (HPAIV) H5N1, clade 2.3.4.4b, in fattening geese. Given the increasing threat of HPAIV outbreaks in European poultry, particularly in free-range geese, the research aims to identify effective vaccination strategies to mitigate disease impact and reduce virus transmission.
The study employed a prime-boost vaccination trial using five different vaccines, incorporating both novel technologies (subunit, vector, and RNA-based vaccines) and traditional whole inactivated virus (WIV) vaccines. The vaccines differed in formulation, manufacturer, and technological platform:
- Subunit vaccine – Contains purified viral proteins, likely the H5 hemagglutinin.
- Viral vector vaccine – Utilizes a non-pathogenic virus to deliver genes encoding the H5 antigen.
- RNA vaccine – Delivers nucleic acid sequences that direct host cells to produce viral antigens.
- Whole Inactivated Virus (WIV) vaccines (two formulations) – Contain killed virus particles with native viral proteins.
Immune responses were assessed through serological assays (HI and ELISA). The vector and RNA vaccines required a booster dose to elicit sufficient antibody titers, whereas some WIV and subunit vaccines induced early seroconversion following a single dose. A subsequent challenge trial with a virulent HPAIV H5N1 strain demonstrated that all seroconverted geese were fully protected from clinical disease, although sterile immunity was not achieved. Vaccinated birds shed significantly less virus, but low levels of viral excretion persisted.
Vaccine Type | Efficacy
- Subunit vaccine: Induced seroconversion after a single dose, providing full clinical protection. A booster was not initially required to elicit protective immunity.
- Vector vaccine: Required a booster to raise antibody titers above the protective threshold (≥4 log₂); post-boosting, it conferred complete clinical protection, though sterile immunity was not achieved.
- RNA vaccine: Also required a booster to achieve adequate antibody levels; following boosting, it offered full clinical protection, though low-level viral shedding was observed.
- Whole Inactivated Virus (WIV) vaccines: Induced seroconversion after the first dose in some birds; booster doses enhanced antibody titers and conferred protection against clinical disease.
Vaccination markedly protected geese from severe disease caused by HPAIV H5N1, reducing both clinical signs and viral burden. While vaccinated birds exhibited diminished virus shedding, limited excretion persisted, indicating the potential for subclinical transmission. Novel technology vaccines (vector and RNA) required booster doses to achieve protective immunity but provided full clinical protection thereafter. Subunit and certain WIV vaccines promoted faster seroconversion following a single dose. Overall, all tested vaccines reduced disease severity and viral load but did not achieve sterile immunity. Incorporating these vaccines into control programs may enhance disease management in geese production systems, although continued surveillance and research into transmission dynamics remain essential for comprehensive eradication strategies.
