#18,363
Now that HPAI H5 has become a global concern, and is significantly impacting poultry, egg, (and in the United States) dairy production, there are renewed calls for the use of H5 vaccines to protect captive birds, and potentially, even dairy cows.
Admittedly, it sounds like an easy solution for a serious threat, as a number of nations (China, Vietnam, Indonesia, Egypt, France, Mexico, etc.) already embrace poultry vaccination against HPAI.
While 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, often due to poorly designed and/or applied vaccines.
- In 2012's Egypt: A Paltry Poultry Vaccine, researchers examined the effectiveness of six commercially available H5 poultry vaccines used in Egypt and found only one actually appeared to offer protection.
- Six years later, another study (see Sci. Reports: Efficacy Of AI Vaccines Against The H5N8 Virus in Egypt) found `. . . most of the commercial poultry H5 vaccines used in the present study were ineffective. . . '
- More recently, in 2023's WUR: 2 of 4 H5 Poultry Vaccines Tested Appear Effective Against H5N1, found ineffective vaccines were still being marketed.
Study: Recombinant H5N2 Avian Influenza Virus Strains In Vaccinated Chickens
EID Journal: Subclinical HPAI In Vaccinated Poultry – China
For obvious reasons, it is imperative that only highly effective vaccines are used, and that they are properly, and consistently updated and applied. This becomes increasingly challenging as the antigenic diversity of HPAI viruses increases around the world.
When done properly, poultry vaccination appears to have a place in the control of HPAI. But done improperly, it has the potential to make a bad problem very much worse (see Vaccines: Vaccination and Antiviral Treatment against Avian Influenza H5Nx Viruses).
Most captive birds would likely require more than one vaccination over their lifetime, and regular testing that can differentiate infected from vaccinated animals (DIVA) would be needed to prevent `asymptomatic spread' of the virus.
Culling and/or quarantine would still be needed for `breakthrough' infections. A different vaccine, schedule and testing regimen would likely be required for non-avian livestock.
None of this would be cheap, or easy to accomplish. All reasons why 90% of the world's nations still don't use HPAI H5 vaccines. While long advocating `stamping out' of infected poultry vs. vaccination, in recent years WOAH has become more open to the idea of vaccinating against HPAI.
WOAH Terrestrial Code 10.4.1
The use of vaccination against avian influenza may be recommended under specific conditions. Any vaccine used should comply with the standards described in the Terrestrial Manual. Vaccination will not affect the high pathogenicity avian influenza status of a free country or zone if surveillance supports the absence of infection, in accordance with Article 10.4.28., in particular point.
Vaccination can be used as an effective complementary control tool when a stamping-out policy alone is not sufficient. Whether to vaccinate or not should be decided by the Veterinary Authority on the basis of the avian influenza situation as well as the ability of the Veterinary Services to implement the vaccination strategy, as described in Chapter 4.18.Yesterday the UK's DEFRA released a Joint Taskforce Policy Paper on the vaccination of poultry against HPAI - which for now - remains off the table. I've only posted some excerpts from the report, so follow the link to read it in its entirety.
Standards for diagnostic tests and vaccines, including pathogenicity testing, are described in the Terrestrial Manual.
Policy paper
Published 7 March 2025
Since October 2021 an unprecedented number of high pathogenicity avian influenza (HPAI) outbreaks have been reported throughout Europe and in many regions of the world.
The impact of HPAI on poultry producers is significant, which is why we continue to reiterate the importance of robust biosecurity measures. Where disease occurs, early reporting, rapid diagnosis, and robust disease control measures help to minimise the spread of disease and mitigate its effects on the wider poultry industry.
These control measures include movement restrictions, culling and disposal, cleansing and disinfection, epidemiological investigations and surveillance.
1. Current HPAI vaccination policy
The current UK policy on vaccination to protect birds against HPAI is not to permit the vaccination of birds (outside of zoos in England and Northern Ireland) either for disease prevention or as a disease control response.
While preventative vaccination in poultry is recognised as a potential disease control measure and authorised H5 specific vaccines are available in the UK (Nobilis Influenza H5N2 which has marketing authorisations which could allow its use in Great Britain and Northern Ireland, and Innovax-ND-H5 which is authorised throughout the EU and according to the Windsor Framework could be marketed in Northern Ireland), their use is not without issues. Whether vaccination of birds against highly pathogenic avian influenza virus (HPAIV) is allowed requires a change in UK policy.
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.
As such, vaccination of birds may mask infection by increasing the time taken to detect and respond to detection of the virus. If appropriate surveillance is not put in place, this could result in a vaccinated flock being infected without detection as well as potentially creating a false sense of security, resulting in a possible relaxation of biosecurity and vigilance, further undermining the combined effectiveness of all measures to control the disease.
In addition, there are several practical and commercial disadvantages relating to the use of vaccines for high pathogenicity avian influenza which could present significant logistical and cost challenges to industry.
It will be necessary to be able to differentiate infected birds from vaccinated birds and to have accredited DIVA (differentiating infected from vaccinated animals) tests in place to ensure vaccination does not adversely affect surveillance and exports of poultry and their products to other countries.
The government continues to invest in avian influenza research and monitors the current situation with vaccine development and its usage internationally.
A joint industry, cross government ‘avian influenza vaccination taskforce’ has been established to make recommendations for the use of vaccination of poultry as a preventative measure against HPAI in the UK.
The avian influenza vaccination taskforce continues to review the reliability and validity of new vaccination data. This includes the definition of the epidemiological unit and how it affects the surveillance sampling and testing regime for vaccinated flocks. It also includes the costs, benefits, trade impacts and practicalities of different surveillance options.
The taskforce recognises these issues and supports the principles of vaccination to help mitigate the animal and public health impacts of HPAI. However, its advice will need to adapt to the dynamic nature of infectious diseases. This includes where we continue to see significant spread of the disease, despite control measures, like culling, biosecurity and housing order controls.
Adoption of vaccination will also require a thorough cost benefit analysis with respect to both the producer and government following the establishment of a proportionate surveillance strategy for vaccinated flocks.
The consideration of how game birds might be included in vaccination and surveillance schemes (considering their different production systems, movements, biosecurity, and risk factors) is also under discussion by the taskforce.
The United States began seriously investigating the practicality of using HPAI vaccines a decade ago, after the first introduction of H5N8/H5N2 into North America in late 2014 (see March 2015 CIDRAP report USDA at work on poultry vaccine for H5N8, H5N2).
While that work continues - and last August the USDA Announced the 1st Field Trial Of An H5N1 Vaccine For Cattle - the logistics of implementing any national poultry/cattle vaccination campaign would be daunting.
Although poultry vaccination may become our best (or only) control option in the future, it is well worth doing everything in our power to get it right, before proceeding down that slippery slope.
