Avian influenza: let’s not lose sight of the vaccination strategy
By Carel du Marchie Sarvaas
1. The human and animal cost of avian influenza
Throughout 2025, health authorities around the world had to cull an average of 4.3 million chickens, turkeys, ducks and geese per month due to AI, not for food, but because of the presence or even the threat of avian influenza. Many of them were healthy animals that authorities feared might become infected in the future.
The 2025 figures, though incomplete, only add to the stratospheric global death toll from avian influenza, with more than 633 million poultry lost — both infected and healthy — since 2005.
We often soften this reality with technical language, speaking of “depopulation”, “culling” or “eradication”. But these terms obscure the underlying reality that healthy animals are lost not because they are sick, but because systems have failed to prevent disease.
2. Effective vaccines, but blocked by trade policies
What makes these losses even harder to accept is that effective vaccines exist, yet they remain unused in the vast majority of poultry flocks worldwide. The uncomfortable truth is that this is not primarily due to scientific uncertainty or negligence, but is the result of decisions dictated by outdated trade policies.
Vaccination against avian influenza can — and typically does — lead governments of importing countries to immediately ban imports from a vaccinating country. This can devastate farms, rural communities and entire economies. Faced with a brutal but rational choice, countries therefore opt to cull flocks during outbreaks in order to preserve access to commercial markets.
The reason vaccination leads to import bans is that vaccinated birds are currently indistinguishable from infected ones, meaning importing countries suspend trade to minimise risk.
3. The failure of mass culling policies and the spread of disease
But this strategy has failed. Despite mass culling, outbreaks continue to rise and avian influenza is spreading to an ever-growing number of locations and species. Avian influenza outbreaks in mammals more than doubled in 2024 compared with 2023, reaching Antarctica for the first time and increasing the risk of further spread and transmission to humans.
Meanwhile, although avian influenza cases in humans are not non-existent, they remain highly unlikely, and the probability of these leading to severe illness or death is even lower — but this is not the case in birds. This “omnipresence” of the virus in the environment — and consequently on commercial farms — results in tens of thousands of affected birds, driving a greater risk of viral mutation and generating a growing risk of new strains that could spread more widely.
4. The urgency of overcoming trade barriers
Countries can no longer afford to let trade concerns hamper our ability to vaccinate. Governments must focus on removing the barriers that prevent the use of prevention before the costs to animals, people and economies increase still further. Vaccination does not have to be an all-or-nothing strategy. There is common ground where vaccines are used strategically to limit the spread of avian influenza, while avoiding risks to disease-free countries.
5. Practical solutions: strategic vaccination and regionalisation
For example, permitting the vaccination of laying hens would help strengthen protection against avian influenza without affecting the export of broilers or poultry meat.
Currently, trade restrictions are applied if any poultry — whether laying hens, turkeys, ducks or broilers — in an exporting country is vaccinated against avian influenza. But in many countries, the majority of eggs are consumed domestically, meaning there is no need to distinguish an infected hen from a vaccinated one for the purposes of cross-border movements.
Vaccination need not trigger national trade bans either. When used in defined areas to contain outbreaks under strict surveillance, trade can continue from unaffected regions. This regionalisation approach is already being used for diseases such as foot-and-mouth disease.
Another way to limit the spread of avian influenza is to vaccinate only specific species. France protected its poultry sector by vaccinating ducks with “DIVA” vaccines that allowed vaccinated animals to be distinguished from infected ones. This facilitated certification protocols with trading partners and allowed trade to continue. The vaccination programme cost €105 million — almost 15 times less than the €1.4 billion in losses sustained during the 2021–22 avian influenza crisis.
Relying solely on biosecurity lockdowns and culling measures has failed. Trading partners must begin working together to remove barriers to vaccine use and allow at least partial, targeted vaccination in the short term, while long-term systemic reforms are implemented.
Avian influenza has already caused enormous losses to poultry producers and global food supplies — whether measured in animal lives, farm incomes or public expenditure on culling and farmer compensation. But the toll will increase exponentially if the disease continues to mutate and jump from species to species, threatening human health, food security and animal welfare.
The strategies employed to date have been insufficient and have resulted in the unnecessary loss of millions of animals. Meanwhile, vaccines are proven tools for disease prevention and can be deployed both broadly and precisely — but only if countries agree on how to do so without paralysing trade.
We have the tools to change the current trajectory. What is missing is a system that allows them to be used. Until then, the cycle of outbreaks and mass culling will continue.
Source:
“Grippe aviaire : ne passons pas à côté de la stratégie de vaccination”. European Scientist. Carel du Marchie Sarvaas –
About the author:
Carel du Marchie Sarvaas is the Executive Director of Health for Animals, a global animal health association representing the 10 largest producers of animal health products.
Find out more:
-. News on Vaccination of poultry farmers and staff in contact with production birds to prevent zoonosis risks.
-. News on Vaccination of production birds to prevent AI outbreaks
-. Avian Influenza on NeXusAvicultura
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