Flu vaccine providing important protection despite new subclade
Source: gov.uk (2025-11-11)

UKHSA’s early season data shows vaccination remains best defence alongside good respiratory hygiene as flu activity rises.

Children and adults across England are receiving strong protection from this year’s flu vaccine, despite the emergence of a new subclade driving an unusually early flu season.

New data published today (https://www.gov.uk/government/publications/pre-print-early-influenza-virus-characterisation-and-vaccine-effectiveness-in-england-in-autumn-2025) as a pre-print by the UK Health Security Agency (UKHSA) shows the 2025/26 vaccine is currently 70 to 75% effective at preventing hospital attendance in children aged 2 to 17 years and 30 to 40% effective in adults.

The early findings confirm the vaccine provides important protection even though a drifted influenza A(H3N2) strain (also now known as subclade K) currently dominates cases in England, so the protection levels observed in children are particularly encouraging this year. Flu vaccine effectiveness varies from season to season but is typically between 30 to 60%, with higher vaccine effectiveness typically seen in younger age groups.

High effectiveness in younger age groups may also provide indirect protection to other groups through reduced transmission.

UKHSA assesses vaccine effectiveness by studying whether people who have been vaccinated are less likely to attend or be admitted to hospital with influenza.

The UK flu programme uses technologically advanced vaccines optimised for each patient group. The observed levels of effectiveness seen in this study are similar to typical flu seasons and this demonstrates that enhanced vaccines can provide strong protection, even when the virus has evolved.

Flu activity has risen unusually early this season, with increases first seen in teenagers and young adults, followed by younger children. Almost all cases have been influenza A, with 84% identified as the H3N2 subtype where testing was available.

Dr Jamie Lopez Bernal, Consultant Epidemiologist for Immunisation at UKHSA said:

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. The high vaccine effectiveness in children strengthens the case for ensuring all eligible young people get vaccinated. When more children are protected, it helps stop the spread of flu to others around them.

Importantly, whatever strains do circulate here this winter, we can be confident that the vaccine will still help to protect those most vulnerable from developing serious illness and being hospitalised. We strongly encourage all those eligible to get vaccinated against flu as soon as possible – it remains our best defence against serious illness.

Good respiratory hygiene is also key in preventing the transmission of flu and other viruses. Anyone with symptoms - including high temperature, cough, and feeling tired or achy – should minimise contact with others, especially those who are vulnerable. Wash hands regularly and ensure indoor spaces are well ventilated, and if you need to go out with symptoms, consider wearing a face covering.

Dr Thomas Waite. Deputy Chief Medical Officer said:

Flu can be an unpleasant infection for many and life threatening for some; Vaccination is the best form of defence.

Early data from the UKHSA shows this year’s vaccine is continuing to provide good protection against flu variants circulating this year.

The flu season has started early this year. Now is the time to get vaccinated if you are eligible.

Vaccination remains the most effective way to protect against flu. Eligible groups include children aged 2 to 17, adults aged 65 and over, pregnant women, and those with certain health conditions. Book your appointment today (http://www.nhs.uk/bookflu).

For more information on how our vaccines protect against different flu types visit our latest blog (https://ukhsa.blog.gov.uk/2025/11/11/how-well-will-i-be-protected-from-flu-this-year-with-the-current-uk-influenza-vaccines) post.