Influenza activity in England has risen above the baseline level used by the UK Health Security Agency, which issued a briefing note to the NHS after publishing its weekly surveillance report for week 44. The report, covering 26 October to 1 November and published on 5 November, puts laboratory positivity at 7.6 per cent, up from 6.8 per cent the previous week. Even so, the agency describes overall influenza circulation as low.
Hospital admissions for influenza rose to 2.83 per 100,000 from 2.51. Emergency department attendances for influenza-like illness increased slightly and sat above the levels expected for the time of year, a rise driven mainly by adults aged 45 to 64.
Vaccination uptake is behind last season in most eligible groups at the same point in the campaign. Among people aged 65 and over, 59.1 per cent have been vaccinated, against 61.5 per cent a year earlier. Coverage in clinical risk groups is 27.9 per cent, compared with 28.9 per cent. Pregnant women are the exception, at 31.1 per cent against 29.7 per cent.
Those coverage figures are given for the same point in the season, which makes them comparable with last year’s campaign rather than with its final total. The largest gap is among people aged 65 and over, where coverage is 2.4 percentage points below the equivalent week of 2025.
Signal in the data
The report notes that some circulating A(H1N1)pdm09 viruses in subclade D.3.1.1 show low reactivity with antisera raised against the vaccine component. The agency says the effect of this on vaccine effectiveness is not yet clear. Low reactivity in a laboratory test is a signal to be tracked as the season develops, not a finding that the vaccine will fail, and the agency has drawn no conclusion from it.
Elsewhere in the respiratory picture, COVID-19 activity decreased and remains low. Respiratory syncytial virus activity increased from baseline, with positivity highest in children under five.
One week above the line
Baseline is a surveillance threshold rather than a measure of pressure on hospitals. Passing it means influenza is circulating at a level at which the agency expects to see an impact, and the briefing note is the mechanism for telling the NHS where activity now sits. One week above the line does not establish a trend on its own.
The description of circulation as low therefore sits alongside rising positivity and rising admissions without contradiction. The threshold marks the level at which impact is expected, not the level at which services are under strain, and the agency’s assessment of the season as a whole is not changed by a single week’s figures.
Adults aged 45 to 64 are not offered vaccination on age grounds, because the age-based offer begins at 65. Coverage in that band is recorded only where people qualify through a clinical risk group, which is one reason the emergency attendance figures are read separately from the uptake figures.
Uptake below last season’s path in the two largest eligible groups means a larger share of those groups is unprotected than a year ago, though the report does not put a number on the additional people involved. The clinical risk group gap is 1.0 percentage point, and coverage among pregnant women has risen by 1.4 points.
What happens next
The agency publishes the report weekly through the winter, so positivity, admissions and emergency attendances will be updated in the next edition. The briefing note gives providers the current assessment, and later editions will show whether the rise continues or settles back below the threshold.
For adults in the eligible groups who have not been vaccinated, the campaign remains open, and the weekly figures will show whether coverage closes the gap with last season. How far the D.3.1.1 viruses spread, and how they respond to the vaccine in use, is the question the agency has said it cannot yet answer.
