Concerns Over Upcoming Flu Season
Scientists are raising concerns that North America might face a challenging flu season this winter, primarily due to the rapid emergence of a variant that doesn’t align well with the seasonal flu vaccine.
Canadian health officials highlighted this in a recent paper, indicating that a surprising variant of the H3N2 flu, labeled subclade K, had appeared toward the end of the flu season in the Southern Hemisphere. This subclade K is likely to become a predominant variant in both the U.S. and Canada, and it seems that the efficacy of our vaccines this winter might not align with earlier expectations.
“Even though mismatched vaccines can still offer some protection against circulating variants, we should enhance our monitoring,” the researchers mentioned in their paper.
The Mismatch Dilemma
During peak flu seasons, several variants of influenza A and B viruses spread among people. It typically takes about nine months to produce sufficient vaccines for an entire hemisphere, prompting scientists and health authorities to convene biannually to predict which variants are likely to circulate, thus determining which strains the seasonal flu vaccine should cover. This forecasting involves tracking flu strains worldwide.
Usually, their predictions are relatively accurate, allowing vaccines to provide at least moderate protection against illness. However, flu viruses are constantly evolving, and they can develop mutations—known as drift—that may render them quite different from initial expectations. This situation appears to have occurred with the latest H3N2 variants.
The researchers noted that an increase in H3N2 variants with worrying mutations appeared during last winter’s flu season, possibly contributing to a severe flu outbreak in the U.S.
More recently, a further drifted variant of H3N2—subclade K—surfaced toward the end of the Southern Hemisphere’s winter. Health officials project that this lineage will dominate among A(H3N2) viruses for the upcoming Northern Hemisphere season.
There’s still a chance that subclade K might not spread extensively within North America, given the presence of other circulating flu variants. However, things don’t seem too promising on that front. In the UK, officials have indicated an early start to the flu season, with a significant number of cases linked to subclade K, leading hospitals to brace for increased flu-related admissions.
Additionally, the fragmented state of public health in the U.S. could complicate efforts to control the flu. Recent funding cuts and staff reductions at the CDC and other health agencies—instigated during the Trump administration—raise concerns about preparedness.
The Importance of Vaccination
Despite the grim outlook, vaccines are still a crucial tool against flu this season. Other flu strains covered by the vaccine can still offer protection, and a mismatched vaccine may help prevent severe outcomes, including fatality. Fortunately, there’s some encouraging news.
The UK Health Security Agency recently revealed data from its flu surveillance program, finding that despite the variant mismatch, the vaccine shows an estimated effectiveness of 70% to 75% in preventing hospitalizations for children and 30% to 40% for adults.
“These findings support the idea that this season’s flu vaccines remain important for both children and adults, even with the emergence of the new subclade,” remarked Jamie Lopez Bernal, a consultant epidemiologist at the UKHSA.
So, it’s still a good idea to get vaccinated as soon as possible. However, with the current mismatch, practicing good hygiene is especially crucial—stay home if you’re unwell, and consider wearing a mask in high-risk situations for added protection, preferably choosing well-fitting masks like KN95 or N95.
