Health Protection Agency
Publication date: June 2012
Following the intense influenza activity observed in 2010/11, seasonal influenza activity in 2011/12 in the United Kingdom through several indicators was low and late. The peak GP influenza-like illness consultation rates were the lowest on record in England and Wales. Clinical indices of activity peaked in February 2012 with community syndromic indicators not breaching any early warning thresholds during the season. Despite the low activity overall in the community, many outbreaks of acute respiratory infection associated with influenza outbreaks were reported, predominantly in care homes for the elderly. Despite high influenza vaccine uptake rates in many of these institutions, deaths were often reported in association with these outbreaks.
Admissions to hospital and to intensive care, and subsequent fatalities, were reported in all age groups, though the largest proportion of cases was in over 65s, with an increase in the average age of these cases compared to the previous season. Excess all-cause mortality was detected in 2011/12 limited to the over 65 year age group, with excess deaths coinciding in time with peak respiratory syncytial virus (RSV) and influenza virus activity in December and February respectively.
Influenza A(H3N2) was the dominant subtype detected with virological activity corresponding to clinical activity. Influenza B viruses were also detected, though a smaller proportion was reported compared to 2010/11. Few A(H1N1)pdm09 viruses were detected this season.
In England, the proportion of people aged 65 years and over who received the 2011/12 seasonal influenza vaccine reached 74.0% by the end of the season, a slight increase on the previous year. For people under 65 years in a clinical risk group, a slight increase in uptake to 51.6% was seen. The highest uptake rates across the UK in clinical at-risk groups were seen in Northern Ireland. Vaccine uptake in England in healthy pregnant women was 25.5% and 50.8% in pregnant women with an underlying clinical risk factor; a small decrease in both groups compared to 2010/11. Influenza vaccine uptake by frontline healthcare workers in England was 44.6% by 31 January 2012, an increase compared to the previous season.
Elsewhere in Europe, influenza A(H3N2) was the dominant virus with variation in the level of activity. The level of activity in the UK was low compared to reports in other European countries. Globally changes in the circulating B lineage viruses, and a proportion of A(H3N2) viruses differing from the strain included in the 2011/12 northern hemisphere vaccine, have prompted changes in the A(H3N2) and B strains in the WHO influenza vaccine recommendations for 2012/13.
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Last reviewed: 22 June 2012