US officials last week said they were moving bulk vaccine from CSL Seqirus that closely matched the virus into finished shots that could provide 4.8 million doses of vaccine.
European health officials told Reuters they were in talks to acquire CSL's pre-pandemic vaccine.
Canadian health officials said they had met GSK , maker of Canada's seasonal flu shots, to discuss acquiring and manufacturing a pre-pandemic bird flu vaccine once its seasonal flu production capacity was freed up.
An estimated 20 per cent of the US milk supply shows signs of the virus, authorities say. (AP PHOTO)
The actions follow the explosive spread of a new strain of bird flu that emerged in late 2020 and has caused unprecedented numbers of deaths among wild birds and domestic poultry and has begun infecting many mammal species.
In March, US officials reported the first outbreak of the virus in dairy cattle, which has infected dozens of herds in nine states and two dairy workers.
The US Food and Drug Administration has estimated that 20 per cent of the US milk supply shows signs of the virus, indicating a wider spread is likely.
Human exposure to the virus in poultry and dairy operations could increase the risk the virus will mutate and gain the ability to spread easily in people.
"All of our efforts need to be focused on preventing those events from happening," said Matthew Miller, co-director of the Canadian Pandemic Preparedness Hub at McMaster University.
"Once we have widespread infections of humans, we're in big trouble."
Dr Angela Rasmussen, a virologist at the University of Saskatchewan, said she had been in discussions with US and Canadian officials about using vaccines to protect workers following the virus' spread into new mammal species.
Dawn O'Connell, of the US Administration for Strategic Preparedness and Response, said the government was "looking closely" at the possibility of vaccinating farm workers and others in close contact with the virus.
The US has contracts with CSL and GSK to test pre-pandemic vaccines that more closely match the circulating virus than older H5N1 vaccines in the stockpile.
The US was moving forward with the CSL vaccine, a Department of Health and Human Services official confirmed.
Discussions about pre-pandemic vaccine use were going on at government levels and among scientists in a number of places, including in the UK, said Wendy Barclay, chair in influenza virology at University College, London, who also researches avian flu for the UK Health Security Agency.
The European Commission's Health Emergency Preparedness and Response Authority was working on a joint procurement of CSL Seqirus's vaccine to "potentially prevent a pandemic", spokesman Stefan De Keersmaecker told Reuters.
A CSL spokeswoman said the company had been in talks with several governments about procuring vaccines since 2022.
Those requests had accelerated with the US outbreak, she said.
