Breakthrough in Avian Influenza Research: A New Vaccine Candidate for H5N1 Protection

Strategic Insights -

Research conducted at the Bern Animal Park in Switzerland has led to the development of a new vaccine candidate for avian influenza (bird flu) that provides long-lasting protection against the H5N1 strain. According to the study, the vaccine, VSV G(H5), was tested on 317 captive birds across 23 species and showed no side effects, with birds developing strong antibody responses after two doses. The research suggests that the vaccine is safe and effective for broad protection against H5N1 across diverse avian species.

Key Takeaways:

  • The highly pathogenic avian influenza (HPAI) H5N1 viruses have caused mass mortality in birds and infected over 50 mammalian species, including humans, with approved avian vaccines remaining limited.
  • The VSV G(H5) vaccine, encoding a modified H5 hemagglutinin from a 2022 Swiss HPAI isolate, was tested on chickens and showed strong neutralizing antibody responses and full protection from lethal H5N1 challenge without viral shedding.
  • The vaccine was administered to 317 captive birds across 23 species in Bern Animal Park and Basel Zoo, with no side effects observed and birds developing strong antibody responses after two doses.
  • Birds without prior exposure to H5Nx developed strong antibody responses after two doses, while previously exposed birds responded after one vaccination.
  • After one year, 98.7% of the vaccinated birds retained significant neutralizing antibody levels, indicating durable protection.
  • The study suggests that the VSV G(H5) vaccine is a safe, effective vaccine candidate for broad protection against H5N1 across diverse avian species.

Statistics:

  • Over 50 mammalian species, including humans, have been infected by the H5N1 virus.
  • The HPAI H5N1 strain has caused mass mortality in birds.
  • 98.7% of vaccinated birds retained significant neutralizing antibody levels after one year.
  • 317 captive birds across 23 species were tested with the VSV G(H5) vaccine.
  • Two doses of the VSV G(H5) vaccine were required for birds without prior exposure to H5Nx to develop strong antibody responses.
  • One dose of the vaccine was sufficient for previously exposed birds to respond.

Sources:

  • Stefan Hoby et al. "RNA replicon vaccination confers long-lasting protection against H5N1 avian influenza in 23 zoo bird species." Nature Communications, 2025;16(1):9245.
  • Nature Portfolio. Nature Communications can be contacted at: Heidelberger Platz 3, Berlin, 14197, Germany.
  • TB & Outbreaks Week. "Findings from Stefan Hoby and Co-Authors Provide New Insights into Avian Influenza (Bird Flu) (RNA replicon vaccination confers long-lasting protection against H5N1 avian influenza in 23 zoo bird species)." November 4, 2025; p 1330.