Flu Case Numbers Jump In Scotland

3rd December 2025

According to the latest reports from Public Health Scotland (PHS), laboratory-confirmed flu cases rose by 45 % in one week — from 555 to 805.

Over roughly the same period, hospital admissions due to flu increased from 279 to 391.

The rise has been driven by a drifted strain of influenza A(H3N2), and the virus is affecting "all age groups," which is unusual for this early in the flu season.

Flu-related GP consultations and hospitalisations have hit levels not seen since the 2017/18 season.

Why this matters

The early and steep rise suggests this could turn into a particularly severe flu season with pressure on hospitals and increased risk for vulnerable people (older adults, children, people with health problems).

Mortality data for 2025 already shows that flu-related deaths in Scotland are at their highest for 45 years.

Authorities are urging people to get vaccinated and to take precautions (hand hygiene, staying home when sick, avoiding hospital visits if symptoms are mild) to help reduce spread.

There are indications that this year's UK Health Security Agency (UKHSA) and global public-health authorities believe the current flu vaccine may be less effective than in some seasons — but "less effective" doesn't mean "useless." Here's what we know, and why experts still recommend getting vaccinated.

Why effectiveness might be lower this season

Flu vaccines work best when they closely match the flu virus strains that end up circulating.
World Health Organization

For the 2025/26 season, a new "drifted" variant — H3N2 subclade K — seems to be spreading in parts of the UK and internationally.

Early data suggest that the vaccine may offer less protection against infection with that strain — i.e. more “breakthrough” flu cases than in a well-matched season.

But there’s still good protection — especially against severe disease.

According to recent UKHSA early-season data: for children (2-17 years old), the flu vaccine is currently showing about 70-75% effectiveness at preventing hospital visits due to flu. For adults, effectiveness against hospitalisation is estimated at 30-40%.

That level of protection — even if imperfect — can substantially reduce the risk of severe illness, hospitalisation or complications. This is consistent with what long-term data show for flu vaccines: even in “imperfect match” years, vaccines usually reduce illness severity and spread.
World Health Organization

Public-health experts argue that this season “is precisely a time when getting vaccinated makes sense,” because even partial protection helps both individuals and the community.

What “less effective” really means in real life

A mismatch or drift in circulating flu strains doesn’t always mean the vaccine fails — but it can mean higher chances of catching flu anyway, especially the milder or more typical “infection” forms.

The protection tends to be greater for children and less so for older adults or those with weaker immune systems.

Protection can also wane over time — particularly if vaccination happens early and flu circulation peaks later.

The current flu vaccine appears to offer less protection against some infections than in perfect-match seasons — especially given the emergence of H3N2 subclade K.

But it’s still your best defence against severe illness, hospitalisation and complications from flu.

Getting vaccinated remains especially important if you’re in a “higher-risk” group (older age, chronic illness, pregnant, etc.), or live/work with vulnerable people.