A recombinant herpesvirus of turkeys (HVT) vector co-expressing the IBDV VP2 protein and the H9N2 avian influenza HA protein induced high protection against both infectious bursal disease virus and H9N2 influenza virus in chickens, according to a study published online 12 October 2026 in Veterinary Microbiology.

The work comes from a research team led by corresponding author Aijun Sun, with co-authors Yuanyuan Zhang, Xiuwen Yang, Yunzhe Kang, Wenhui Zhu, Shaoyan Qi, Yuanyuan Sun, Yuxin Chen and Guoqing Zhuang. The group engineered HVT — a vector already widely used in commercial poultry vaccination — to carry and express the two protective antigens simultaneously in a single construct.

Why co-expression matters at the farm level

Infectious bursal disease virus and H9N2 subtype avian influenza virus are two of the most economically significant viral pathogens in poultry production across regions where both circulate. Current practice typically requires separate vaccines, delivered through separate handling, to cover each disease.

A single HVT-vectored construct expressing both VP2 and HA would consolidate that coverage into one preparation. The study reports that the bivalent recombinant induced high protection against challenge with both pathogens in chickens, which is the core practical result for broiler and layer operations evaluating vaccination protocols.

What the vector approach changes

HVT-based vectors have an established track record in poultry: they replicate in the bird, sustain antigen expression, and can be administered in ovo or at hatch, which fits automated commercial vaccination lines. The new findings add a second antigen, H9N2 HA, onto the established IBDV-VP2 carrier strategy, demonstrating that the platform can carry a combined load while maintaining protection against both targets.

For veterinarians advising poultry producers, the result points toward a possible route to fewer injections, less bird handling and simplified cold-chain and logistics per flock cycle — outcomes that matter most in high-throughput hatchery settings.

Species and scope of the findings

The study was conducted in chickens, the species in which both IBDV and H9N2 cause the greatest production losses. The authors characterize the protection induced by the recombinant as high against both pathogens.

Readers should note what the publication record does not yet establish. The study is a peer-reviewed report in Veterinary Microbiology, available online as of 12 October 2026; it is not a statement of regulatory approval. Any commercial bivalent HVT product based on this construct would require separate registration with the relevant authority — in the United States, USDA CVB, and in the European Union, EMA — before it could reach the market.

Public-health and companion-animal context

H9N2 is an avian influenza subtype with zoonotic relevance, as it has infected humans in sporadic cases and contributes genetic segments to other circulating influenza A viruses. A poultry vaccine reducing H9N2 replication and shedding would carry a public-health benefit alongside the production benefit, by lowering viral load in the bird population.

The findings carry no direct implication for companion-animal medicine; the work is specific to poultry health.

What comes next

The study, published 12 October 2026 in Veterinary Microbiology by Zhang, Sun and colleagues, establishes that a single recombinant HVT co-expressing IBDV VP2 and H9N2 HA can protect chickens against both pathogens — a result that now sets up field-evaluation and regulatory pathways as the logical next steps.