To date, most of the world’s largest poultry producers have discounted vaccinations because of fears that the vaccines could mask the spread of bird flu and hamper trade. The shots don’t completely stop transmission, but vaccinated birds show no signs of illness — potentially giving the virus a chance to spread silently, even increasing the long-term risk of it being transmitted to humans.
Similarly, some argue that the adoption of vaccinations is a concession that the disease has become endemic and will never be eradicated. There have also been concerns that vaccinations could pressure the virus to mutate further.
At VIV Asia – a major livestock conference on the outskirts of Bangkok where more than 45,000 people from around the world have gathered to share ideas and technology – many want to hear from countries that have embraced avian flu vaccinations for poultry decades ago.
Their experiences offer critical data and valuable lessons as governments from Ecuador to the Netherlands consider whether it is time to change tack.
Eradicating the virus ‘may not be possible’
“We have had success with vaccination for a long time and it has saved our poultry industry,” Maureen Kalona Kandou, head of science and innovation at Vaksindo, an Indonesian manufacturer of animal vaccines, told the Telegraph this week.
“We’ve seen an increase in inquiries … because the topic of vaccination has become interesting in the Western Hemisphere. “This is such a widespread outbreak that eradication may no longer be a possible solution,” he added.
In Indonesia, breeders or layers – poultry that live much longer than broilers raised for meat – have been vaccinated since 2004. The strategy was adopted because the disease was already endemic in wild birds in the country and compensation to farmers whose flocks were killed is not economically viable for the government.
However, the approach did not initially control the virus because the vaccines were not targeted enough, said Dr Teguh Prajitno, managing director of Animal Health at JAPFA – an Asian agricultural company, of which Vaksindo is a subsidiary.
Then, in 2011, Indonesia stopped importing international vaccines and instead adopted locally produced, “homologous” vaccines that match the strains circulating in the country.
“Since we started using the homologous vaccine, outbreaks in poultry, but also in sampling of live birds in the market, have become less and less,” said Dr. Prajitno, who has advised the government on vaccination strategies, during a keynote address at VIV Asia. “So this was a very, very important milestone for Indonesia to start controlling bird flu.”
Jabs have been updated twice to ensure they still effectively target viruses that are spreading, added Ms Kalona Kantu.
“The key to effective vaccination is follow-up,” he said. “We’re using the same approach that’s used on the human side for annual flu shots … so we can track the strains that are spreading and match our vaccines.”
In Indonesia, the vaccination strategy aims to “prevent clinical disease, mortality and of course minimize economic losses,” Dr Prajitno said. But it has also been developed to reduce the amount of virus circulating.
This does not put humans at greater risk, but has reduced the threat of spread to other species or humans, he argued. To date, only 11 percent of the 189 human cases reported in Indonesia have been linked to commercial poultry – in his view, live markets pose a far greater risk to humans.
He added that no other international concerns have materialized either. For example, there is “no evidence” that any new variants or strains have come from vaccinated flocks, and a “compartmentalization” approach – where certain areas are designated as avian flu-free zones – has allowed exports to continue.
In China, where vaccinations have also been a mainstay of bird flu measures since the early 2000s, there is also data suggesting that poultry vaccination has helped reduce human infections.
In 2017, the country introduced a new inactivated vaccine for H7N9 and saw the prevalence of the disease drop by more than 90%.
But more importantly, the scientists said in a paper published in 2018, only three cases of human H7N9 were reported after the shots were distributed. From October 2016 to September 2017, 766 human cases were reported in China, “showing that poultry vaccination has successfully eliminated human infection with the H7N9 virus.”
Biosecurity ‘only way to prevent contamination’
The experiences of countries in Asia are now informing debates elsewhere, as governments reassess their vaccination calculations amid the unprecedented outbreak, the rising financial cost of culling and increased pressure from farmers to switch equipment.
Reports say the UK government is “actively reviewing” its vaccination policy, while the US has begun testing potential poultry vaccines and is in discussions with industry leaders about a large-scale rollout.
Last month, the EU also agreed a new, harmonized vaccination strategy. Designed to allow the continued trade of vaccinated poultry within the bloc, these rules include surveillance and biosecurity measures aimed at detecting possible infections in vaccinated flocks.
Some countries, such as France, are also in talks with trading partners outside the EU about exporting vaccinated poultry, while the Netherlands, Hungary and Italy are testing vaccines with a view to launching them in the autumn. Further afield, Mexico launched an emergency program last year, while Ecuador this month said it planned to vaccinate two million birds.
But some warn that roadblocks remain. In the UK, Dr Christine Middlemiss, the chief veterinarian, told BBC Radio Four this week that vaccines that prevent transmission and match the viruses in circulation are needed to properly tackle the threat.
Dr Prajitno also admitted that current vaccines do not stop the spread of bird flu.
“We have to emphasize, when we talk about vaccination, that biosecurity is the only way to prevent infection,” he said. “The vaccines we have can’t prevent the infection, what we’re doing is really just controlling it … and reducing the viral load in the field.”
This becomes critical when circulation reaches such a high level that it is nearly impossible to eradicate the virus, he added. Now, the question for governments around the world is whether that point has been reached.
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