This year's flu season has taken an unusual turn, commencing several weeks earlier than expected and placing significant strain on healthcare services across the United Kingdom and worldwide.
The Predominant Strain: A/H3N2 Subclade K
The virus driving the current outbreak is the A/H3N2 strain, specifically subclade K. This marks a distinct shift from recent seasons, which were largely dominated by the A/H1N1 strain. According to a report by Ignacio López-Goñi for The Conversation, this variant has now been detected on every continent and is responsible for approximately 90 per cent of current cases.
Despite its widespread and rapid circulation, health officials note a crucial point: subclade K does not appear to be more virulent or cause more severe illness than other common flu strains. The primary challenges lie elsewhere.
Concerns Over Immunity and Vaccine Match
Two major concerns are heightening vigilance among public health experts. First, there may be lower population immunity to the A/H3N2 family of viruses compared to others. Second, and more pressing, is the issue of vaccine efficacy.
The seasonal flu vaccine administered this year was formulated to protect against an older strain of A/H3N2. Early indicators suggest it may offer reduced protection against the newly dominant subclade K. This potential mismatch is a key factor being closely monitored.
Vaccination Remains a Critical Defence
In light of these developments, health authorities are issuing a clear and strong recommendation. Vaccination is still strongly advised for all eligible individuals.
The rationale is twofold: the unusually early onset of the season increases the risk of widespread infection, and the vaccine continues to provide vital protection against severe disease, hospitalisation, and complications, even if its effectiveness against mild infection from subclade K is diminished.
Getting the jab remains the single most effective step people can take to safeguard their health and reduce pressure on the NHS during this premature and active flu period.
