New Flu Variant Spreads Fast, Vaccination Still Key: WHO

Amid an early start to the Northern Hemisphere influenza season, a new variant of the virus is rapidly gaining ground, but vaccination remains the “most effective defence,” the UN health agency said on Tuesday.

Influenza and other respiratory viruses are surging, Dr Wenqing Zhang, Unit Head for Global Respiratory Threats at the World Health Organization’s Department of Epidemic and Pandemic Threats Management, told reporters in Geneva. She said this season is marked by “the emergence and rapid expansion of a new A(H3N2) virus subclade.”

The new variant—known as J.2.4.1, or subclade K—was first identified in August in Australia and New Zealand and has since been detected in more than 30 countries.

“Current epidemiological data do not indicate an increase in disease severity, although this genetic shift represents a notable evolution in the virus,” Dr Zhang said.

She explained that influenza viruses are constantly evolving, which is why vaccine composition is regularly updated. WHO tracks these changes, assesses public health risks and issues vaccine composition recommendations twice a year through the Global Influenza Surveillance and Response System (GISRS), in collaboration with global experts.

The new variant is not included in the composition of the latest vaccines produced for the Northern Hemisphere influenza season. Still, early evidence suggests that current seasonal vaccines continue to offer protection against severe disease and reduce the risk of hospitalisation.

WHO estimates there are around one billion cases of seasonal influenza globally each year, including up to five million cases of severe illness. Up to 650,000 deaths annually are attributed to influenza-related respiratory disease.

“Vaccination remains our most effective defence, including against drifted strains, particularly for high-risk populations and those who care for them,” Dr Zhang said.

She cited early estimates of vaccine effectiveness against the new variant from a recent study in the United Kingdom, describing the findings as “quite promising.” The data showed the vaccine to be around 75 percent effective against severe disease and hospitalisation in children and about 35 percent effective in adults.

Dr Zhang warned that the upcoming holiday season could drive a further surge in respiratory illnesses and urged advanced planning, higher vaccination uptake and stronger health system preparedness.

She also advised countries to strengthen laboratory diagnostics, maintain year-round disease surveillance and participate in the WHO GISRS network, which includes influenza centres in 130 countries and a dozen reference laboratories.

Responding to questions about the United States’ future participation in the network following its decision to leave WHO in January 2026, Dr Zhang stressed that global cooperation remains essential. She said timely detection and characterisation of new strains can save lives by shortening the time needed to develop effective vaccines.