Are we seeing an early flu season? What we know so far about this year's strains

Early indications point to an earlier flu season this year, with flu activity in September already surpassing the same period over the past four winters. Although levels remain relatively low, an upward trend suggests the season may begin sooner than usual. This early start has primarily been driven by cases in the 18- to 24-year-old age group.

This year, two flu A subtypes, H1N1 and H3N2, are circulating in England. The flu vaccine typically offers protection against all three main types of flu: influenza A(H1N1), A(H3N2), and influenza B. The vaccine should generally provide broad protection against the strains circulating during that winter season. However, this year, the A(H1N1) strain has drifted from the vaccine strain, which has not yet been determined if it will significantly impact vaccine effectiveness.

Last winter, a drifted H3N2 strain, subclade K, emerged after the vaccine composition for the Northern Hemisphere was finalized. Despite this, the vaccine remained effective, and overall flu activity and mortality levels were lower than the previous year. Research has shown that vaccination still provides substantial protection against severe illness, with vaccinated children being 65 to 70% less likely to attend or be admitted to the hospital with flu, and adults 20 to 30% less likely.

Since flu activity is already higher than expected, getting vaccinated sooner rather than later is recommended for optimal protection. If you are eligible for a free flu vaccine, it is advised not to delay, as it could help safeguard against serious illness this winter.