PARIS, March 21 (Reuters) - China may be using some substandard
poultry vaccines to fight bird flu that could allow birds to keep spreading the
virus despite not showing symptoms, a top animal health expert said on Tuesday.
Christianne Bruschke, a member of the bird flu task force at the
Paris-based World Animal Health Organisation (OIE), said the vaccines made in
China at the Harbin Veterinary Institute conformed to international standards
and were fully effective.
"But there are local companies in China that produce vaccines and it's
possible these don't have the efficacy of those made at Harbin," she told
Chinese officials have said their vaccines are effective and that no
healthy-looking bird has yet been found carrying H5N1.
But there have been outbreaks in areas where poultry were supposedly
already vaccinated and this has raised the possibility that birds are continuing
to spread the virus.
"There are two possibilities," Bruschke said. "Either the vaccine is not
strong enough, or that it is a good vaccine but not administered properly.
Vaccines have to be given twice to be fully effective, maybe that is not
"When a vaccine is not effective enough, it could prevent clinical signs
from showing but the bird could still spread the virus. That's certainly a
possibility," she said.
And she said poultry that had not been properly vaccinated may also pose
a health risk to humans although it was difficult to quantify the danger.
Research in Europe, which did not import vaccines from China, showed
drugs stopped the spread of the virus, she said.
"The vaccines are, when administered properly according to manufacturers'
instructions, effective in preventing the spread in chickens and ducks," she
said, adding that more research was needed on other bird species.
The Netherlands, France and Russia have announced plans to vaccinate some
of their poultry against bird flu. But Dutch farmers have mostly chosen to wait
before vaccinating their birds because they fear a negative impact on exports.
David King, the British government's chief scientific adviser, said the
often close contact between humans and chickens in China meant that vaccines
were particularly necessary there.
"The Chinese are using a number of different vaccines and one of the
vaccines it is claimed has a high efficacy," he said.
"But we couldn't possibly use a vaccine that hadn't been fully through
the European procedures of testing," he added. (Additional reporting by
Elizabeth Piper in London)