Historically, avian influenza control centered on stamping out infected flocks, movement bans, and biosecurity—with vaccination as a last resort. But the evolving threats of H5N1 clade 2.3.4.4 and 2.3.2.1c, expanding geographic incidence, mammalian spillovers, and the collapse of culling as a full prevention tool prompted WOAH to pivot. At its 90th General Assembly, WOAH recognized that vaccination must be part of a broader, scientifically-grounded strategy that includes surveillance, DIVA testing, and exit plans to preserve trade and welfare . Millions of birds have died or been culled globally, and wildlife and humans are increasingly affected—making vaccination not just an option, but a necessity .
1. 🧬 Global Strategy 2024–2033: Integrated, One Health & Risk‑Based
In March 2025, FAO and WOAH released the Global Strategy for the Prevention and Control of HPAI (2024–2033) under GF-TADs . Key objectives:
- Strengthen biosecurity across poultry value chains
- Enhance real-time surveillance of H5Nx Gs/GD lineage
- Promote sustainable poultry systems resilient to disease shocks
- Prioritize One Health integration—human, animal, wildlife health
- Mobilize public-private cooperation across all stakeholders
- Advocate for adaptive policies including vaccination when contextually appropriate
A major roadmap event—a global technical webinar—was held on March 3, 2025 to secure commitments in English, French, and Spanish
2. 🧬 Scientific Principles & Strategy: Matching Vaccines to Circulating Strains
WOAH emphasizes the need for vaccines that closely match field virus isolates, similar to human flu vaccine strain matching. Its OFFLU AIM initiative provides laboratories and vaccine manufacturers with updated antigen reagents to test vaccine efficacy regularly . EU’s EFSA also recommends preventive vaccination in high-risk zones and emergency vaccination within 3 km of outbreaks, all anchored in ongoing strain surveillance . Vaccine efficacy must be validated, and antigenic drift must be tracked to maintain protection .
3. 🔁 Defining Vaccination Strategies: Preventive vs. Emergency Use
Vaccination serves different roles depending on epidemiological context:
- Preventive vaccination: Used in high-risk poultry zones before outbreaks occur. Targets breeder flocks, layers, and outdoor-reared birds to minimize infection onset and spread .
- Emergency protective vaccination: Applied in defined zones around an outbreak to halt spread. Must be rapid, targeted, and integrated with surveillance and movement controls.
- Emergency suppressive vaccination: A broader strategy to reduce transmission when immediate culling and containment might be less feasible or ethical .
All WOAH-endorsed vaccination must be coupled with exit plans, surveillance, and trade-compatible DIVA tools .
4. ⚖️ Trade Implications & DIVA Strategy
One main concern preventing widespread vaccination has been trade barriers: many importing nations refuse products from vaccinated flocks, suspecting potential viral carriers. But WOAH calls these restrictions "unjustified" if proper surveillance and DIVA protocols are implemented . The DIVA strategy (Differentiating Infected from Vaccinated Animals) uses molecular markers to distinguish vaccinated birds from infected ones—a model successfully used in Italy (H7N1/H7N3 outbreaks), which allowed safe trade resumes . In early 2025, the US and Canada lifted bans on French duck imports after verifying France’s vaccination safety and DIVA-based approaches .
5. ✅ Global Experiences: France, China, and Beyond
France pioneered nationwide duck vaccination in October 2023, becoming the first major poultry exporter to do so. Despite initial import suspensions, export resumed after safety assurances. By 2024, French poultry output recovered 12.1% above 2019 levels thanks to vaccination safeguards against HPAI . China offers the longest historical precedent: it vaccinated nearly 100 billion poultry starting in 2005, helping eliminate H5N1 from domestic stock before new strains emerged . Lessons: scale matters, government support is critical, and surveillance must follow vaccination.
6. 🌱 Surveillance, Monitoring & Implementation Challenges
Vaccination is just one part of the vaccine-control equation. WOAH stresses a robust surveillance system to detect infections in vaccinated and wild birds, using PCR testing, serological sampling, and wild bird monitoring . The FAO-supported WOAH/FAO OFFLU framework helped expand lab capacity, tested over 60 outbreaks, and strengthened global antigen matching through AIM reagents deployment in over 50 labs worldwide . Monitoring must also extend to mammals, particularly as H5N1 has infected seals, sea lions, and humans in recent outbreaks .
7. 🧪 Vaccine Types & Deployment Methods
Currently in the EU, there is one authorized poultry HPAI vaccine for chickens, with limited data available for other species and production systems. Vaccines may include inactivated killed virus or vectored vaccines (eg. Vectormune HVT-AIV approved in EU early 2025) designed for mass administration via aerosol or injection at hatching . In ovo vaccination—delivering vaccine into the egg during incubation—is being explored for early immunity and streamlined roll-out in large hatcheries . Vaccine administration logistics remain challenging, especially for broilers (short lifespans) where manual injection is impractical for large flocks.
8. 🌏 Coordinated Global Governance & One Health Integration
WOAH’s 90th General Session passed resolutions emphasizing no one-size-fits-all, but calling for coordinated national strategies consistent with WOAH standards and trade continuity . FAO parallels this with the GF-TADs and PMP-TAB frameworks promoting One Health—blending animal, human, and environmental health perspectives in vaccination strategies . USA funding cuts to FAO bird flu programs in early 2025 raised concern among U.S. farmers, as surveillance gaps hamper global vaccine strain matching and early warning systems .
9. 📉 Risks, Limitations & Critical Concerns
Antigenic drift can reduce vaccine efficacy if strains are not updated timely. DIVA surveillance must allow early detection of breakthrough infectionsTrade partners may still impose restrictions unless vaccine programs meet stringent WOAH/DIVA criteria .Operational challenges include limited cold chains, need for mass administration infrastructure, vaccine licensing delays, and manual labor constraints in large commercial flocks .Wildlife spillover complicates eradication—vaccinating domestic flocks alone doesn’t prevent introduction via wild birds; surveillance of wildlife remains critical .🔮 What’s Missing and Needs Further Focus
🔍 Final Thoughts: A Coordinated Path Forward
WOAH’s call for coordinated global vaccination action represents a strategic shift recognizing that culling and biosecurity alone no longer suffice. When vaccination is backed by strain matching, DIVA capacity, surveillance programs, trade-compliant frameworks, and One Health coordination, it becomes a viable pillar for durable control of HPAI. Countries like France and historical precedents in China show that integrated vaccination can restore production and minimize welfare impacts while preserving exports. However, success hinges on surveillance systems, lab networks, antigenic monitoring, and global communication.
❓ FAQs
Q1: Can vaccinated birds still spread bird flu?
A: Yes. Vaccination reduces severity and mortality but doesn’t eliminate viral shedding. That's why surveillance through DIVA and PCR is critical.Q2: Will vaccination harm poultry exports?
A: Not if vaccine use complies with WOAH standards and includes DIVA. France’s example shows trade restrictions can be lifted once safety is validated .Q3: How often must HPAI vaccines be updated?
A: Regularly—similar to human flu. The OFFLU AIM system supports ongoing antigenic matching between circulating viruses and vaccine strains .Q4: Who decides which countries vaccinate?
A: Each national Veterinary Authority, in consultation with industry, must tailor vaccination strategies to local epidemiology, resources, and trade objectives .Q5: Is vaccination a permanent solution?
A: No—vaccination is part of an integrated control strategy including biosecurity, surveillance, movement controls, and exit plans once risk declines .Q6: If vaccinated birds still shed virus, why vaccinate at all?
A: Vaccination lowers viral loads and mortality, slowing transmission. When combined with DIVA surveillance, it supports early detection even in vaccinated populations.