#19,075
With agricultural losses mounting from avian influenza, more and more farmers are clamoring for the ability to protect their flocks with vaccines, yet many countries remain slow to embrace that strategy.
Although we've seen some impressive success stories (see OFID: Avian H5, H7 & H9 Contamination Before & After China's Massive Poultry Vaccination Campaign), we've also seen some significant failures (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China), often due to poorly designed and/or applied vaccines.While poultry vaccination would seem to be the ideal solution, its success rate over the years has been inconsistent, and we've seen evidence that suboptimal formulations and application can help drive viral evolution.
The problem is that a vaccine that is only partially effective may merely mask the symptoms of infection, but still allow the virus to spread stealthily and continue to evolve (producing vaccine-induced escape mutants).
Eleven months ago, in NPJ Vaccines: Impact of Inactivated Vaccine on Transmission and Evolution of H9N2 Avian Influenza Virus in Chickens, a report warned that inactivated vaccines have failed to prevent - or even reduce - H9N2 in China's poultry, and may have driven viral evolution (including mammalian adaptations).
In 2023 WOAH (formerly the OIE) announced a policy shift (see WOAH: Rethinking Avian Influenza Prevention and Control Efforts) that recommended a comprehensive control strategy that integrates vaccination with other measures (including testing & culling if needed).But most countries - including the United States, Canada and the UK - have yet to authorize HPAI poultry vaccines, although many are studying the matter.
Why Canada doesn’t currently vaccinate poultry against HPAI
Canada has historically maintained an HPAI response strategy focused on disease eradication and does not currently vaccinate poultry to protect against HPAI. The scale and duration of the ongoing outbreak, however, has increased global interest in exploring vaccination as a tool for disease management. Some countries already use vaccines as a preventative measure.
Last March's UK Joint Taskforce Policy Paper: Vaccination of Birds Against HPAIV (bird flu) continues to promote eradication, warning:
Use of avian influenza vaccine may reduce poultry mortality and clinical signs of the disease following infection. However, vaccinated birds can still become infected, shed virus, and transmit the virus to other vaccinated or unvaccinated birds, mammals and humans.Last July the UK published an independent report outlining the many challenges inherent in adopting a vaccination strategy, which discussed the possibility of conducting a limited and targeted turkey vaccination trial as a first step.
Today the Defra announced that a six-month trial has begun (see below), on a small group of birds under strict supervision.
First the press release, after which I'll have a postscript.
Press release
New avian influenza vaccine trials begin in UK
New targeted trial in turkeys will test vaccine efficacy as part of fight to protect wild and captive birds
From:Department for Environment, Food & Rural Affairs, Animal and Plant Health Agency and Baroness Hayman of Ullock Published 5 March 2026
Highly pathogenic avian influenza (HPAI) vaccine trials have started today (Thursday 5 March) in a major step forward in the fight against the disease.
New trials will explore the potential for the latest vaccines to protect birds, focusing on turkeys only in England, providing valuable insight into how well vaccines work in the field, how surveillance can be managed to retain trade and how vaccines can help manage the disease.
The scale of avian influenza outbreaks in the UK and Europe within the last few years has been unprecedented, causing devastation for bird keepers on the frontline and the poultry sector. Annual outbreaks cost the UK Government and industry up to £174m each year. The disease has significantly impacted both captive and wild birds globally since 2020.
Turkeys have been selected as a priority species for further research as they are highly susceptible to avian influenza, with outbreaks resulting in severe clinical signs with rapid and elevated mortality rates.
The trial will sample a small group of birds under strict supervision following approval from the Veterinary Medicines Directorate (VMD) and using UK/ EU authorised vaccines. Vaccinating poultry against bird flu is not currently allowed more widely in the UK.
Biosecurity Minister Baroness Hayman said:
We know what a terrible toll this disease has annually on our farmers and poultry sector.
The start of new vaccine trials are a significant step forward in our fight against this disease and will contribute to global research efforts. We are hopeful vaccines can be used in the UK as an additional tool to control bird flu to protect the UK’s biosecurity and food supply.
UK Chief Veterinary Officer Christine Middlemiss said:This targeted trial is going to be really key for our understanding of how HPAI vaccines can be effectively used for disease control in the UK. They have the potential to be a really valuable additional tool in helping us protect birds from infection.
Stringent biosecurity will always remain our best defence and I urge all bird keepers to continue to take the steps needed to prevent avian influenza spreading onto their premises.
Animal and Plant Health Agency Avian Influenza Disease expert Professor Ashley Banyard said:
The scourge of this disease has impacted both captive and wild birds populations globally since 2020. The impact has varied annually, which makes forecasting of disease events very difficult.The trial will evaluate how vaccines could be safely and effectively integrated into the UK’s disease control strategy, generate data on vaccine efficacy and contribute to the growing international body of research on HPAI vaccination. It will help us understand how vaccines can be effectively used in the UK as an additional tool to control bird flu and provide valuable information on vaccine effectiveness and contribute to global research efforts, during these challenging times,
Assessing the ability of these vaccines to generate an immune response in turkeys will give a good indication of the suitability of these vaccines as tools to protect birds against H5N1.
The potential benefits of HPAI vaccination are being considered in several countries experiencing similar challenges to the UK. In Europe there are ongoing trials of vaccines in Italy and the Netherlands.
Stringent biosecurity remains the best defence against the disease. All bird keepers should familiarise themselves with the steps they need to take to prevent bird flu and avoid any potential for it to spread. Remaining vigilant for signs of disease, and reporting this promptly, will help to keep birds safe.
The trials will last for 24 weeks and will provide insight into the final recommendations of the UK HPAI vaccination taskforce.
ENDS
Notes to editors: In July 2025, the Taskforce published a report outlining the current status and challenges of vaccination, exploring future options for vaccination of birds in different sectors including a cost benefit analysis and a recommendation for a domestic field vaccination trial in turkeys.
With poultry vaccination programs, the devil is always in the details.
Last August, in Vaccine X: H5N1 Highly Pathogenic Avian Influenza Vaccination: Seroresponse of Mexican Poultry in the 2022–2024, we looked at the first two rounds of HPAI poultry vaccination in Mexico.
While seroconversion and seroprotection rates approached or exceeded 80% in many states, looking at the breakdown of the 20 states included in the first round, 7 (33%) scored considerably lower, with 2 states in single digits.
The authors noted:
These limitations were evident in period one, mainly across southeastern Mexican states because they did not mount an immune response after vaccination with seroconversion and seroprotection rates less than 10 % of their population.
It is likely that some of the critical points of the vaccination plan were not fully met or were not carried out properly.
And that's the rub. What may work perfectly under strict supervision can fall apart in the real world due to poor or careless execution. And when that happens, it can afford the virus new opportunities to spread or evolve.
Surveillance and frequent testing of vaccinated flocks is also crucial in order to detect `silent' infections. This can't be a `vaccinate and forget' strategy.Although poultry vaccination may well be our best (or only) control option going forward, it is imperative that it is done consistently, properly, and with continually updated vaccines.
Else we risk making a bad problem considerably worse.
