Highly pathogenic avian influenza (HPAI) continues to disrupt poultry production worldwide. But according to Taoufik Rawi, DVM, a poultry veterinarian at Boehringer Ingelheim focused on global respiratory disease challenges, the industry is no longer dealing with the same virus it faced a decade ago.
The currently circulating H5 clade is more infectious, affects far more bird species and has increasingly spilled over into mammals, including dairy cattle in the US. At the same time, the virus has become more persistent globally, creating continuous pressure on commercial poultry production rather than the cyclical outbreaks seen in the past.
Those changes are driving renewed discussion around vaccination as part of long-term HPAI control strategies, alongside biosecurity and surveillance.
Here, Rawi discusses how the virus has evolved, why vaccination is gaining momentum globally and what future HPAI control strategies could look like for the poultry industry.
Q: What is different about the current HPAI situation compared to previous outbreaks?
A: The biggest change is that the virus has become much more efficient at spreading and persisting globally.
The current H5 clade circulating worldwide, 2.3.4.4b, is much more infectious than previous strains. Compared to the virus circulating during the 2015 to 2016 outbreak period, dramatically fewer viral particles are needed to infect birds today.
At the farm level, the infectivity changed tremendously. To infect a chicken with the 2015 virus, you needed around 500,000 particles. With the current virus, you need around 3,000 particles. To infect a duck, you need only around 100 particles.
The virus has also expanded into many more species. Historically, HPAI circulation was largely associated with waterfowl and a relatively limited number of bird species. Since 2020, however, hundreds of species have been affected.
That changed the epidemiology completely. Some species, especially seabirds, helped introduce the virus into new geographies like South America. At the same time, spillover into mammals has become increasingly common, including infections in sea lions, cats and dairy cattle, suggesting the virus has become better adapted to infecting multiple species.
Q: Why are traditional HPAI control strategies under pressure?
A: Historically, HPAI control relied primarily on surveillance and stamping out infected flocks.
That approach was more effective when outbreaks occurred in waves and the virus disappeared for periods of time. But the current epidemiological situation is different because the virus is now continuously present in wild bird populations.
We are very far from eradication. The virus survives in wild birds, and we continue seeing introductions into commercial poultry.
As the virus became more widespread and environmentally persistent, the poultry industry and scientific community increasingly recognized that surveillance and depopulation alone were not enough to effectively manage the disease.
That shift has led organizations such as the World Organisation for Animal Health (WOAH) and the Food and Agriculture Organization of the United Nations (FAO), along with many scientists, to support integrating vaccination into broader HPAI control strategies.
From a scientific perspective, vaccination is increasingly viewed as a necessary addition to HPAI control because the virus is no longer behaving like a short-term epidemic threat.
Q: How does vaccination fit into HPAI control programs?
A: HPAI control is really based on three core elements: biosecurity, vaccination and surveillance.
Biosecurity acts as the physical barrier intended to keep the virus from entering poultry farms. Vaccination increases birds’ resistance to infection and helps reduce virus shedding if infection occurs.
What you want to do is prevent the virus from entering the farm. But if infection happens, vaccination helps reduce shedding and reduce the environmental impact of the virus. That reduction in shedding is important because it helps limit spread to nearby farms and reduces secondary outbreaks.
Surveillance also remains essential, even in vaccinated systems, because infected flocks still need to be identified quickly and removed when necessary.
The combination of those three approaches is what helps reduce outbreaks and stop the epidemiological cycle.
Q: Why does vaccination remain a complicated issue in some countries?
A: The biggest challenge is trade. Historically, some countries worried vaccination could allow infected flocks to go undetected if birds did not show obvious clinical signs. Because of that concern, surveillance programs become critically important in vaccinated systems.
If you continuously monitor flocks with surveillance, there is less risk of silent infections.
Countries implementing vaccination must also demonstrate to trading partners that their surveillance systems are robust enough to rapidly detect infections. France, for example, introduced vaccination alongside extensive surveillance programs and discussions with importing countries.
It becomes a bilateral discussion between exporters and importers. You need to show the surveillance model you are implementing and build confidence that infections will still be detected.
At the same time, international attitudes toward vaccination are evolving. WOAH now considers that vaccination should be implemented without automatically impacting trade status. The infection itself is what should impact trade.
Q: What factors are shaping the vaccination discussion in the US poultry industry?
A: In the US, the discussion is particularly complex because HPAI affects sectors differently.
Long-lived birds such as layers, breeders and turkeys, as well as ducks, have been much more heavily impacted than broilers. The egg and turkey industries are very interested in vaccination because they are directly affected by the disease and have incurred significant losses since 2022.
At the same time, the US broiler industry exports about 14% of its poultry meat – significantly more than other sectors – magnifying concerns about possible trade implications tied to vaccination.[1]
Considering these dynamics, future vaccination strategies may need to account for regional differences in production. States or sectors with high concentrations of long-lived birds, such as layers and turkeys, may face different risk-benefit considerations than broiler-heavy regions focused on export markets. Ultimately, any decisions regarding vaccination would be made by US government authorities.
At the same time, European experience is providing more data on how targeted vaccination programs can work in practice. Recent trials in layers and turkeys have shown strong vaccine efficacy, including major reductions in outbreak risk.[2] Dutch government trials, for example, have demonstrated that vaccination can reduce outbreak risk in layers by 70% to 90%.
Those findings are helping shape broader industry discussions around whether vaccination could reduce the impact of HPAI in the most vulnerable sectors while balancing trade considerations.
Q: What advances are shaping newer HPAI vaccines?
A: One major focus is broader protection against the wide range of H5 viruses circulating globally.
COBRA technology (computationally optimized broadly reactive antigen) is one example. Rather than targeting only a single field strain, the technology was designed to create broader protection across relevant circulating viruses. Vaccines using this approach can provide cross-clade protection against diverse H5 viruses.
Another important development is the use of prime-boost vaccination strategies in long-lived birds, such as layers. In this approach, birds receive hatchery vaccination, followed by a booster vaccination later on the farm. Recent Dutch trials showed this type of program could maintain protection through most of a layer’s production cycle. The protection lasted through at least 84 weeks of age.
Differentiating infected from vaccinated animals — what’s known as DIVA capability — is also critical in vaccinated systems.
Using serology or PCR testing, DIVA-compatible vaccines allow surveillance programs to distinguish infected birds from vaccinated birds, which is important for both disease control and maintaining trade confidence.
Q: Looking ahead, what role could vaccination play in long-term HPAI control?
A: Around the world, vaccination is increasingly being viewed as an essential component of long-term HPAI control because the epidemiological situation has changed so significantly in recent years.
At the same time, vaccination should not be viewed as a standalone solution. Biosecurity, surveillance and stamping out infected flocks remain essential to limiting spread and maintaining safe trade.
But when combined with those measures, vaccination can help reduce outbreaks, limit environmental spread and better protect long-lived poultry populations facing continuous HPAI pressure.
References
1 National Chicken Council. Broiler Chicken Industry Key Facts 2025. Broiler Chicken Industry Key Facts 2025 – National Chicken Council (accessed June 9, 2026)
2 Bouwman KM, de Wit MK, Jansen CA, Fischer EAJ, Velkers FC, Germeraad EA, et al. Lelystad, Netherlands: Wageningen Bioveterinary Research; 2026. Available at: https://doi.org/10.18174/705406
Editor’s note: Content on Modern Poultry’s Industry Insights pages is provided and/or commissioned by our sponsors, who assume full responsibility for its accuracy and compliance.
