Published on 6 May 2026

New vaccination strategies are highly effective against mutating influenza viruses in pigs

This new vaccination strategy is therefore a promising approach for improved control of influenza outbreaks in humans and animals.

Significance of the study

The findings demonstrate that prime–boost vaccination strategies are critical for inducing effective antibody responses against antigenically drifted influenza viruses. In particular, the neuraminidase (NA) antigen included in the vaccine elicits broadly reactive antibodies that complement the protection provided by hemagglutinin (HA)-specific responses. Notably, the study provides compelling evidence that intramuscular immunisation alone can fully prevent viral shedding and transmission of drifted strains, opening new avenues for influenza control in both humans and animals.

• Study overview

  Seasonal influenza viruses frequently evade immune recognition through antigenic drift, necessitating regular updates of conventional vaccines and often resulting in suboptimal protection. Researchers at the IVI therefore investigated two vaccination strategies targeting pandemic H1N1 viruses in a pig model:

  • Homologous prime–boost: A two-dose intramuscular regimen using replication-incompetent RNA virus vectors encoding either the HA or NA antigen of the 2009 pandemic H1N1 virus.
  • Heterologous prime–boost: A combination approach involving RNA virus–vectored priming followed by intranasal administration of a live-attenuated influenza vaccine (LAIV). Vaccine efficacy was assessed based on antibody responses and viral load following challenge with an antigenically drifted virus.

• Key findings

  • Sterilising immunity: Both vaccination strategies completely prevented viral replication and shedding of the drifted H1N1 virus.
  • Improved safety profile: In the heterologous approach, prior VSV-based immunisation limited prolonged shedding of the live-attenuated vaccine.
  • Broad protection: N1-specific antibodies exhibited cross-reactivity, including activity against the neuraminidase of bovine H5N1 virus.
  • Robust immune response: Even a single intramuscular dose of the VSV-based vaccine induced high levels of virus-neutralising and sialidase-inhibiting antibodies.

• Future directions

  Further research will focus on key questions to better characterise these promising vaccination strategies:

  • Does this approach confer longer-lasting immunity compared to conventional influenza vaccines?
  • What vaccination intervals optimise the booster effect?
  • What is the potential of RNA virus–vectored vaccines encoding neuraminidase alone?

Title
Non-propagating RNA virus-vectored HA/NA vaccine prevents shedding of antigen-drifted H1N1 influenza virus in pigs

Authors
Obdulio Garcia-Nicolas, Lisa Butticaz, Robin Avanthay, Nicolas Ruggli, Artur Summerfield & Gert Zimmer