Trials at Wageningen University have shown two out of four tested vaccines to be effective against bird flu, bringing mass vaccination of poultry one step closer, the agriculture ministry has said.

The vaccines could mean a breakthrough in the battle against the disease which has been ravaging wild bird populations and poultry farms since October 2021 and has caused some six million farmed chickens, ducks and geese to be culled.

Pressure to find an effective vaccine is also increasing, as the highly contagious H5N1 virus has jumped the species barrier and has been found in minks, foxes, otters and seals.

Human contagion is extremely rare but the possibility of another pandemic cannot be wholly discounted, experts have said.

Agriculture minister Piet Adema is happy with the results as a step on the road to mass vaccination. This should happen ‘as soon as it can be done responsibly,’ he said.

The approach to bird flu needs to be ‘more intensive’ the minister said, and ‘requires the active cooperation of European member states, poultry farmers, and the private sector’.

Researchers will be testing the vaccines in the field to find out which circumstances may affect effectiveness, such as the presence of other viruses and the combination with other vaccines.

Depending on the results, this will be followed by a large-scale pilot trial at poultry farms at the end of the year.