New Flu Variant Raises Concerns for Upcoming Winter Season

Health officials are warning that the upcoming flu season in North America may be particularly challenging due to the emergence of a new variant of the H3N2 flu virus, known as subclade K. According to a report from Canadian health officials published in late October 2023, this variant does not align well with the seasonal flu vaccine and could lead to increased illness and hospitalizations.

The subclade K variant surfaced during the latter part of the flu season in the Southern Hemisphere and is now expected to become one of the dominant strains in the United States and Canada. Experts fear that vaccine effectiveness may be lower than anticipated this winter. In their research published in the Journal of the Association of Medical Microbiology and Infectious Disease Canada, scientists emphasized the need for enhanced surveillance to monitor the variant’s spread.

Understanding the Mismatch

Influenza viruses undergo continuous evolution, which can lead to the emergence of new variants. This year, a significant number of H3N2 variants with mutations have been identified, contributing to the severity of the flu season in the Northern Hemisphere. The health officials noted that it typically takes about nine months to produce enough vaccines tailored to the anticipated variants. As a result, predictions regarding which strains will circulate are made twice a year, but with flu viruses constantly changing, these predictions can become outdated.

The emergence of subclade K is a clear example of this drift. Researchers indicated that this variant is projected to dominate the A(H3N2) viruses for the Northern Hemisphere’s 2025-2026 flu season. While there is a chance that subclade K may not spread widely, the likelihood appears grim, especially as the UK has already reported an early flu season, predominantly driven by this variant. Hospitals across the UK are bracing for an increase in flu cases.

Complicating matters further, public health efforts in the United States have faced challenges due to significant funding cuts and staff changes at the Centers for Disease Control and Prevention (CDC) under the administration of former President Donald Trump and Health Secretary Robert F. Kennedy Jr..

The Importance of Vaccination

Despite the challenges posed by the new variants, vaccination remains a critical tool in mitigating the impact of the flu this season. While the vaccine may not perfectly match the circulating strains, it can still provide valuable protection against severe outcomes, including hospitalization and death.

Recent data from the UK Health Security Agency indicates that the current flu vaccine is estimated to be 70% to 75% effective in preventing hospitalizations in children and 30% to 40% effective in adults, even in light of the mismatch. Jamie Lopez Bernal, a consultant epidemiologist for Immunization at UKHSA, stated, “These results provide reassuring evidence that this season’s flu vaccines currently offer important protection to children and adults, despite concerns about the new subclade.”

Given the potential for increased flu activity, health officials recommend that individuals get vaccinated as soon as possible. Additionally, they stress the importance of practicing good hygiene, staying home when ill, and wearing masks in higher-risk settings, particularly well-fitting masks such as KN95 or N95 types, which offer the best protection.

As the flu season approaches, staying informed and prepared will be essential for individuals and communities alike.