Seasonal influenza in Wales /15

Transcription

1 Seasonal influenza in Wales /15 Annual Report Page 1 of 43

2 Summary Taking into account information from all influenza surveillance indicators, the 2014/15 influenza season in Wales saw moderate levels of activity. Circulation of influenza virus in the community was detected in early December 2014 and clinical consultation rates in primary care exceeded the threshold for seasonal activity until early March 2015, although cases of influenza were confirmed at lower levels throughout April. Consultation rates for influenza-like illness (ILI) in general practice were similar in intensity and pattern to those seen during , although the 2014/15 season saw a higher proportion of older patients needing medical attention due to influenza, both in primary and secondary care. This season also saw the highest seasonal excess mortality in England and Wales as a whole for the last nine years. The dominant circulating influenza virus type was A(H3N2), although a smaller number of cases of influenza B were seen later in the season, from March to April, and even fewer case of influenza A(H1N1). The season was characterised by the circulation of drifted influenza viruses, which were not as well-matched to the seasonal influenza vaccine virus strains as usual. As a result of this, estimates of effectiveness of the 2014/15 seasonal influenza vaccine were lower than has been the case in previous seasons. The final adjusted estimate for vaccine effectiveness in the United Kingdom during the 2014/15 season was 34%. Mismatches in seasonal influenza vaccine strains, compared to the dominant circulating viruses, happen from time to time when new influenza virus strains emerge. In the case of the 2014/15 influenza season, it was due to the late emergence and circulation of drifted strains of influenza A(H3) and influenza B viruses, after the period on which the World Health Organisation based its recommendations for vaccine virus strains. On average, in previous years, there has been a good match between circulating strains and influenza vaccine strains, resulting in higher vaccine effectiveness. The seasonal influenza vaccine remains the safest and most effective way to prevent influenza in those most vulnerable. The seasonal influenza vaccine for 2015/16 in the Northern hemisphere includes virus strains that match the drifted viruses which circulated in Wales during 2014/15. More individuals than ever in clinical risk and priority groups in Wales received an influenza vaccine during 2014/15. The universal childhood influenza vaccination programme was extended from children aged two and three years and those in school year seven, to include children aged four years. Coverage of influenza vaccination in pregnant women, measured by an annual point of delivery (post-natal) survey, increased from 70.5% to 72.4%. Although uptake of influenza vaccine in those aged 65 years and older remained stable and those in clinical risk groups decreased slightly, Wales maintains its place as one of the European countries with the highest levels of uptake of seasonal influenza vaccine in vulnerable members of the population. Page 2 of 43

3 Key Findings Although the GP consultation rate for ILI was not unusually high during 2014/15, compared to previous seasons, other indicators showed notable influenza activity and the highest burden of illness was in older adults and the elderly. o The crude ILI attack rate in the community during the peak of activity in England and Wales was 4%. o More than 9,203 patients were diagnosed with Influenza-like illness (ILI) by GPs in Wales throughout the season. o Throughout the season, 611 patients in hospitals were confirmed to have influenza, 85 of whom were in intensive care units. o Thirty-one outbreaks of influenza were reported to Public Health Wales, from nursing homes, residential homes and care facilities, with 311 diagnosed cases. o 2014/15 saw the highest levels of seasonal excess mortality in the past nine years. The season was dominated by influenza A(H3N2), which can affect elderly patients most. Influenza B circulated later in the season. Drifted influenza A(H3N2) and influenza B viruses circulated in the UK, which were distinguishable from the viruses contained in the 2014/15 northern hemisphere seasonal influenza vaccine. Lower estimates of vaccine effectiveness were reported for the 2014/15 seasonal influenza vaccines than has been the case in previous seasons. For the UK, final vaccine effectiveness was 34%. More influenza vaccinations were given in Wales during 2014/15 than ever before, however percentage uptake in the population remained relatively stable or decreased slightly in some at risk groups. Influenza vaccine uptake in those aged 65 years and older in Wales was 68.0% during 2014/15, compared to 68.3% last season. Uptake of influenza vaccine in patients aged six months to 64 years in a clinical risk group was 49.3%, compared to 51.1% last season. Uptake among clinical risk groups was highest in patients with diabetes (64.8%) and lowest in patients with chronic liver disease (42.0%). Uptake of influenza vaccine in pregnant women who went on to give birth during February and March 2015 was 72.4% (measured in an annual survey of women in major maternity units), an increase of 1.9 from 70.5% last year. Uptake of influenza vaccine in people younger than 65 years and recorded as being a carer (including carers who are also in a clinical risk group) was 53.4%. Uptake of influenza vaccine in children aged two to four years, immunised in General Practices, was 36.6%. Uptake of influenza vaccine in School Year 7 aged children, immunised in school immunisation sessions, was 74.3%. Page 3 of 43

4 Uptake of influenza vaccine in Health Board and NHS staff in Wales, reported by Health Board Occupational Health Departments, continues on a positive trend and was 42.9% during 2014/15, an increase of 2.3 from 40.6% last season. Uptake in staff with direct patient contact was 44.3% and exceeded 50% in two health boards and one NHS trust. The total number of individuals recorded as immunised against influenza in General Practice was 723,061 for 2014/15 (based on a 100.0% response rate), compared to an estimated 703,191 last season. This is the fifth year that data on uptake of influenza immunisation in Wales has been collected using the Audit+ General Practice software. This report is based on an overall response rate of 100.0% of General Practices in Wales (99.6% of whom provided data through Audit+). Page 4 of 43

5 Contents Summary... 2 Key Findings... 3 Background... 7 Influenza and influenza-like illness surveillance indicators... 7 Influenza immunisation... 7 Influenza Surveillance Observations from 2014/ Community indicators - GP consultations for influenza-like illness (ILI)... 9 Community indicators - Virological surveillance in the community Hospital indicators - Virological surveillance Hospital indicators - patients in intensive care units Influenza outbreaks in community settings Influenza outbreaks in hospitals Excess mortality during the influenza season Influenza virus characterisation, vaccine effectiveness and antivirals Antigenic characterisation of influenza viruses Effectiveness of the 2014/15 seasonal influenza vaccine in the UK Antiviral prescribing rates Influenza immunisation in Wales 2014/ Data collection Data submission rates Influenza Immunisation uptake Uptake in those aged 65 years and older and those aged six months to 64 years in clinical risk groups Immunisation uptake by risk group Estimated numbers of individuals immunised in Wales in 2014/ Uptake in pregnant women Uptake of Live attenuated intranasal vaccine in children Patients declining influenza vaccination in Primary Care Uptake in Welsh Health Board and NHS Staff Uptake in General Practice staff Page 5 of 43

6 Conclusions References Information about this report Data tables Table 2. Uptake of influenza immunisation in Wales 2014/ Table 3. Uptake of influenza immunisation in those aged six months to 64 years with one or more clinical risks (by risk category), Wales, 2014/ Table 3 (cont). Uptake of influenza immunisation in those aged six months to 64 years with one or more clinical risks (by risk category), Wales, 2014/ Table 4. Uptake of influenza immunisation in pregnant women, with breakdown for those who have another clinical risk condition, Wales, 2014/ Table 9. Uptake of influenza immunisation in those aged six months to 64 years and recorded as being a carer in Wales in 2014/ Page 6 of 43

7 Background Influenza and influenza-like illness surveillance indicators Public Health Wales monitors and reports on influenza activity in Wales throughout the year using a number of indicators. Historically, the main indicator of influenza activity in Wales and in other UK countries has been the rate of consultations in general practices for influenza-like illness (ILI), per 100,000 practice population. The GP consultation rate for ILI in Wales is calculated using data provided from a network of sentinel practices, through Audit+ general practice software. The sentinel GP network in Wales has provided data used for monitoring influenza activity since More recently, a range of indicators from both primary and secondary care have been used in order to provide a wider picture of the burden of influenza and other seasonal respiratory illnesses. During the winter 2014/15, the following influenza surveillance indicators were monitored each week in Wales: Primary care and community indicators GP consultations for ILI Sentinel GP virological surveillance Respiratory related consultations with Out of Hours primary care doctors Influenza related calls to NHS Direct Wales Secondary care indicators Respiratory diagnostic test data for all hospital and non-sentinel GP patients in Wales Respiratory diagnostic test data for patients in intensive care units in Wales The number of hospitals with wards fully or partially closed due to influenza outbreaks (and the number of wards fully or partially closed) Indicators from other settings Outbreaks of influenza and other seasonal respiratory illness reported to the Public Health Wales Health Protection Team, in residential homes, care homes, schools and nurseries In addition, antigenic characterisation of influenza viruses detected and monitoring of winter excess mortality were carried out by Public Health England at an England and Wales level. A telephone survey investigating attack rate of ILI in households in the community was also carried out in England, Scotland and Wales. Influenza immunisation The aim of annual immunisation against seasonal influenza is to protect individuals from influenza and minimise the health impact of seasonal flu on the population of Wales [1]. In Wales in 2014/15, seasonal influenza immunisation was again offered free of charge to all people aged 65 years and over, people aged between six months and 64 years in clinical risk groups (chronic respiratory disease, chronic heart disease, chronic renal disease, chronic liver disease, chronic neurological conditions, diabetes mellitus, and immunosuppression), residents of long-stay care homes, and those who were a main carer for an elderly or disabled person whose welfare may be at risk if the Page 7 of 43

8 carer fell ill. Free seasonal influenza immunisation was also offered to all pregnant women and members of voluntary organisations providing planned emergency first aid. Influenza immunisation is also recommended for all NHS staff providing direct patient care, to protect the staff against influenza and also to protect the patients they care for. The Welsh Government immunisation target was 75% uptake for people aged 65 years and over, and those aged between six months and 64 years in clinical risk groups [1]. For NHS staff with direct patient contact, the target was 50% uptake. In 2014, the annual seasonal influenza campaign was expanded [2] to include all children aged two, three and four years (as at September 2014) and all children in the School Year 7 age group. Both of these groups were recommended to receive live attenuated influenza vaccine nasal spray, with delivery in the two to four year old group being through General Practice and delivery in the School Year 7 group being mainly through school nursing services in Wales. Public Health Wales monitor and report General Practice influenza immunisation uptake rates throughout the seasonal campaign and produce end of season influenza immunisation coverage statistics at national, health board and local authority level. Immunisation statistics contained in this report are not a measure of all those who have been immunised during the course of the immunisation campaign, they represent coverage in those living and registered with General Practices in Wales at the end of the immunisation campaign. During the 2014/15 campaign, Public Health Wales also provided weekly progress reports for all General Practices and health boards in Wales. Page 8 of 43

9 Influenza Surveillance Observations from 2014/15 Community indicators - GP consultations for influenza-like illness (ILI) The Moving Epidemic Method (MEM) threshold [3] of 9.7 ILI consultations per 100,000 was introduced in Wales in 2014 as an indication of when consultation data suggest that influenza may be circulating in the community at low levels. The sentinel GP MEM threshold was first reached during week 46 of 2014 (Figure 1); however the absence of laboratory confirmed cases of influenza in the community and only a small number of sporadic confirmed cases of influenza in hospitals suggested that it was unlikely that this was the true start of the influenza season in Wales. This temporary increase in the consultation rate for ILI may have been associated with the start of respiratory syncytial virus (RSV) activity in Wales, which was noted at this time [4]. Figure 1. Public Health Wales sentinel GP weekly consultation rate for influenzalike illness 2014/15 Consultation rate per 100, Higher than average seasonal activity MEM seasonal activity threshold Historical seasonal activity Low activity Week During week 50 (week ending December 14 th 2014), the consultation rate for ILI in Wales once again exceeded the MEM threshold. At this time, influenza had also been detected in samples submitted from patients in the community by sentinel GPs and in samples from hospitalised patients, indicating it was likely that influenza was circulating in Wales. The sentinel GP consultation rate remained above the MEM threshold for seasonal activity for 12 weeks, until week (week ending March 1 st 2015). The Page 9 of 43

10 peak in consultation rate was seen during week (week ending January 11 th 2015) at 23.2 ILI consultations per 100,000 practice population. The peak in sentinel GP consultation rate for ILI during 2014/15 is the highest seasonal peak since and the second highest since (Figure 2). Figure 2. Public Health Wales sentinel GP weekly consultation rate for influenzalike illness 1996 to 2015 Consultation rate per 100, Epidemic activity Higher than average seasonal (winter) activity Normal seasonal activity (winter) October 1996 April 1997 October 1997 April 1998 October 1998 April 1999 October 1999 April 2000 October 2000 April 2001 October 2001 April 2002 October 2002 April 2003 October 2003 April 2004 October 2004 April 2005 October 2005 April 2006 October 2006 April 2007 October 2007 April 2008 October 2008 April 2009 October 2009 April 2010 October 2010 April 2011 October 2011 April 2012 October 2012 April 2013 October 2013 April 2014 October 2014 April 2015 * Although the overall consultation rate for ILI during winter 2014/15 winter in Wales was similar to that seen during (Figure 3), there was a change in the age distribution of ILI cases diagnosed in general practice (Figure 4). In contrast to previous influenza seasons, the consultation rate for ILI was highest in patients aged 45 to 64 years (369 per 100,000 for the period 2014 week 40 to 2015 week 20); for the preceding four seasons, consultation rates were highest in those patients aged 25 to 44 years. In addition, consultation rates for ILI in older patients aged 65 to 74 years and 75 years and older were at their highest since the influenza season in Wales (226 per 100,000 and 201 per 100,000 respectively). During the period 2014 week 40 to 2015 week 20 (September 29 th 2014 and May 17 th 2015) there were 9,203 consultations with general practices in Wales due to ILI reported to Public Health Wales through Audit+. This is based on an average weekly reporting rate from 92% practices, therefore the true total for ILI cases diagnosed in general practice in Wales will be higher. Only a proportion of those who are infected with influenza will consult with their GP in any given influenza season. During 2014/15, Public Health Wales participated in a telephone survey which aimed to estimate the attack rate of influenza in the community. Based on information from 2,884 individuals in 1,005 households in England, Wales and Scotland, during the peak two weeks of clinical activity, the crude attack rate for ILI (using the WHO ILI case definition of fever >38 degrees Celsius, cough/sore throat and sudden onset of symptoms) in the community was 4%. Page 10 of 43

11 Figure 3. Cumulative consultation rates for influenza-like illness, per season (from 2014 week 40 to ), in sentinel GP patients to 2014/ Consultation rate per 100, Figure 4. Age-group specific cumulative consultation rates for influenza-like illness, per season (from 2014 week 40 to ), in sentinel GP patients to 2014/ < to 4 5 to to to to to and older Consultation rate per 100, All available data from practices providing ILI consultation data, though Audit+, between October 2014 and May 2015 were used to investigate regional differences in timing and intensity of the influenza season (Figure 5). In South East Wales (Aneurin Bevan, Cardiff and Vale and Cwm Taf University Health Board areas), although consultation rates followed the same trend as the national picture, the peak in ILI consultation rate seen during week was higher than the national average (28.5 per 100,000 compared to 25.5 per 100,000 practice population). Page 11 of 43

12 In Mid and West Wales (Abertawe Bro Morgannwg and Hywel Dda University Health Board areas, and Powys Teaching Health Board area) consultation rates for ILI throughout the season appeared similar to the national average. In North Wales (Betsi Cadwaladr University Health Board area) consultation rates for ILI followed a similar pattern to the national average, although the peak seen in week (compared to week for the national average) at 21.9 per 100,000 compared to the national rate of 14.9 per 100,000 at that time. Figure 5. Weekly consultation rates for influenza-like illness in regions of Wales, data from all available practices submitted through Audit+, compared to the national average. 50 National average Consultation rate per 100, South East Wales Mid and West Wales North Wales 13/10/ /10/ /11/ /11/ /12/ /12/ /01/ /01/ /02/ /02/ /03/ /03/ /03/ /04/ /04/ /05/2015 Week ending Community indicators - Virological surveillance in the community Between 2014 week 40 to 2015 week 20 (September 29 th 2014 and May 17 th 2015), 108 samples from patients with acute respiratory symptoms were submitted for testing by 13 sentinel GP practices. Of the 108 samples tested: 31 (29%) tested positive for influenza (29 influenza A(H3) and two influenza B) 10 (9%) tested positive for rhinovirus 6 (6%) tested positive for RSV 6 (6%) tested positive for adenovirus 6 (6%) tested positive for Mycoplasma pneumoniae 5 (5%) tested positive for parainfluenza 4 (4%) tested positive for human metapneumovirus 4 (4%) tested positive for coronavirus 1 (1%) tested positive for enterovirus 35 (30%) tested negative for above pathogens Page 12 of 43

13 The first influenza positive sample from a sentinel GPs was collected in week and the last was collected in week The peaks in sample submissions were seen in weeks one and five 2015 (Figure 6) and the peak in influenza positivity rate was seen in week The 2014/15 winter was dominated by circulation of influenza A(H3), smaller numbers of influenza B virus were detected later in the season. Figure 6. Results from Public Health Wales GP sentinel virological surveillance for influenza and other seasonal causes of respiratory illness. ILI consultation rate per 100, Influenza A positive RSV positive Adenovirus positive Mycoplasma positive Enterovirus Coronaviruses Sentinel GP consultation rate Influenza B positive Rhinovirus positive Parainfluenza positive Human metapneumovirus Bocavirus Negative* Samples (n) Week ( ) 0 Hospital indicators - Virological surveillance During the period 2014 week 40 to 2015 week 20 (September 29 th 2014 and May 17 th 2015) 4,208 patients with symptoms were tested for seasonal respiratory illnesses in Wales. Of these tests, 98.4% were carried out on samples collected from patients in hospital locations and 1.6% were nonsurveillance samples submitted for testing from general practices in Wales. Of the 4,208 patients tested: 611 (15%) tested positive for influenza (420 influenza A(H3), 35 influenza A(H1), 88 influenza A(not further typed) and 68 influenza B) 483 (11%) tested positive for RSV 466 (11%) tested positive for rhinovirus 100 (2%) tested positive for parainfluenza 92 (2%) tested positive for human metapneumovirus 61 (1%) tested positive for adenovirus 36 (1%) tested positive for Mycoplasma pneumoniae Page 13 of 43

14 Sporadic cases of influenza A were detected in 2014 during weeks 42, 43 and 45 (weeks ending 19 th and 26 th of October and 9th November). From 2014 week 48 (week ending 30 th November) influenza virus began to be detected each week in some samples from patients with acute respiratory symptoms in hospitals (Figure 7). The peak in submissions of samples for testing from patients with acute respiratory symptoms was in week one of 2015 (week ending January 4 th 2015, 285 patient samples). Figure 7. Results from respiratory tests carried out on samples from patients in hospitals (and non-surveillance samples from patients in general practice) Influenza A positive RSV positive Adenovirus positive Mycoplasma positive Negative* Influenza B positive Rhinovirus positive Parainfluenza positive Human metapneumovirus dummy 200 Samples (n) Week ( ) Week one of 2015 was also the peak week in terms of percentage of samples testing positive for influenza (36%), 99% of which were positive for influenza A (48% were influenza A(H3), 5% were influenza A(H1) and the remaining samples were influenza A(not further typed)). Smaller numbers of patients were confirmed with influenza B later in the season. Influenza viruses continued to be detected in samples from patients in hospital each week up to week (week ending 5 th July 2015). The peak week for sample test positivity for RSV was week 49 of 2014 (week ending 7 th December 2014) (Figure 7.). Eighteen per cent of all the symptomatic patients in hospitals who were tested for seasonal respiratory pathogens between September 29 th 2014 and May 17 th 2015 were younger than one year of age and 17% were aged 75 years or older (Figure 8), the median age of patients tested was 44 years. Page 14 of 43

15 Figure 8. Numbers of hospital and non-sentinel GP patients screened for seasonal respiratory pathogens between 2014 week 40 and 2015 week 20 (September 29 th 2014 and May 17 th 2015), by age-group; and numbers testing positive for influenza A, influenza B and respiratory syncytial virus (RSV) under 1 1 to 4 5 to to to to to to to and older All respiratory screens under 1 1 to 4 5 to to to to to to to and older Influenza A Patients tested (n) Patients testing positive (n) under 1 1 to 4 5 to to to to to to to and older Influenza B under 1 1 to 4 5 to to to to to to to and older RSV Patients testing positive (n) Patients testing positive (n) Out of all the patients testing positive for influenza A, 51% were aged 65 years and older (of whom 70% were aged 75 years and older, Figure 8); the median patient age was 66.1 years. The median age of patients testing positive for influenza B was 53.5 years, with patients aged 55 to 64 years accounting for 20% of all cases. The median age of patients testing positive for RSV was 0.5 years, 60% of all these patients were younger than one year of age, 14% were aged one to four years and 13% were aged 65 years and older. The median age of patients testing positive for rhinovirus was 2.7 years; and 56% of the patients testing positive were younger than five years of age. The median ages of patients testing positive for human metapneumovirus and Mycoplasma pneumoniae were 4.5 years and 19.7 years respectively. Page 15 of 43

16 Hospital indicators - patients in intensive care units Between September 29 th 2014 and May 17 th 2015, 85 patients in intensive care units (ICU) in Wales were confirmed with influenza (Table 1). Although there were confirmed cases of influenza in patients from most age-groups, the majority (72%) of patients in ICU with confirmed influenza were adults aged 45 years and older. Table 1. Numbers of patients in intensive care units in Wales with confirmed influenza or RSV, from 2014 week 40 to 2015 week 20 Age-group (years) Patients with confirmed influenza Patients with confirmed RSV Under to to to to to to to to and older 23 5 Total Influenza was first confirmed in ICU patients during the 2014/15 season in week (week ending December 14 th 2014, Figure 9) and the last confirmed influenza case was in week (week ending 7 th June Figure 9. Results from respiratory tests carried out on samples from patients in intensive care units in Wales, since October Samples (n) Influenza A positive Influenza B positive RSV positive Rhinovirus positive Adenovirus positive Parainfluenza positive Mycoplasma positive Human metapneumovirus Negative* Sentinel GP consultation rate per 100, Week ( ) GP ILI consultation rate per 100,000 Page 16 of 43

17 Influenza outbreaks in community settings During the 2014/15 influenza season in Wales there were 31 outbreaks of influenza reported in other settings in the community (Figure 10). Thirty of these outbreaks were in nursing or residential care homes and one was in a psychiatric care facility. The majority (77%) of reported outbreaks occurred in South or South East Wales, covering Cardiff and Vale, Cwm Taf and Aneurin Bevan University Health Board areas. A small proportion (23%) occurred in Mid and West Wales, covering Abertawe Bro Morgannwg and Hywel Dda University Health Board areas and Powys Teaching Health Board area. None of the reported outbreaks were from North Wales, covering Betsi Cadwaladr University Health Board area. Figure 10. Outbreaks of influenza reported to Public Health Wales Health Protection Team during the 2014/15 season from community settings Reported oubreaks of confirmed influenza A Reported oubreaks of unconfirmed influenza Reported oubreaks of confirmed influenza B Sentinel GP ILI consultation rate Outbreaks (n) Consultation rate per 100,000 Outbreak report week In total, 366 cases in residents (median 11 cases per care home) were reported, with a median attack rate per care home of 25%. Information on staff cases was available in 30 of the 31 outbreaks, with 85 cases in staff identified (median one staff case per care home). Hospitalisation data were available from 27 of the outbreaks; a total of 36 residents were admitted to hospital (case hospitalisation rate of 11%). Numbers of associated deaths were available for 25 of the outbreaks; a total of 18 deaths in resident cases were reported (case fatality rate of 6%). Influenza immunisation statuses and coverage statistics for residents in the 31 homes were not available. Influenza outbreaks in hospitals Between January 12 th and June 1 st 2015, weekly surveys of numbers of hospitals with wards or units fully or partially closed and the number of wards or units fully or partially closed due to influenza were carried out by Public Health Wales and Health Board Infection Control Teams. From the time that this surveillance started (January 12 th 2015), up to March 9 th 2015 at least one ward or unit in Welsh Page 17 of 43

18 hospitals was reported as fully or partially closed due to influenza in the weekly surveys. The highest weekly numbers of wards fully or partially closed were reported on January 12 th (four wards / units) and February 23 rd (four wards / units). Between March 16 th and June 1 st 2015 there were no wards or units in Welsh Hospitals reported as fully or partially closed due to influenza. Excess mortality during the influenza season Weekly monitoring of seasonal excesses in mortality is carried out at an England and Wales level during the winter period by Public Health England [5]. The expected number of weekly death registrations for any given week are calculated using Serfling regression and estimated numbers of all-cause registered deaths provided by the Office of National Statistics [6]. This is compared to the actual number of registered deaths for the same week to determine whether mortality is higher than expected, resulting in excess all-cause mortality. During the 2014/15 winter period, excess all-cause mortality was seen in week and a large peak was seen between weeks 1 to This is in contrast to the winter period where the numbers of excess deaths were low. A total of 16,415 excess all-age deaths were estimated by Public Health England to have occurred in England and Wales during 2014/15; which is significantly higher than seen during the past nine seasons. Page 18 of 43

19 Influenza virus characterisation, vaccine effectiveness and antivirals Laboratory characterisation of influenza viruses The 2014/15 influenza season in Wales was dominated by influenza A(H3) viruses. The Public Health England Respiratory Virus Unit (RVU) carried out antigenic characterisation on 240 influenza A(H3N2) viruses from across the UK during 2014/15 [5]. Antigenically, the majority (77%) of these viruses were similar to influenza A/Texas/50/2012 H3N2 strain of virus that was included in the 2014/15 northern hemisphere influenza vaccine. However, 55 (23%) were antigenically distinct from the influenza A/Texas/50/2012 strain of virus and similar to the A/Switzerland/ /2013, which is included in the northern hemisphere influenza vaccine. Of the 57 influenza B isolates, belonging to the B/Yamagata/16/88 lineage, which were antigenically characterised by the Public Health England RVU, 52 (91%) showed reduced reactivity in antigenic tests with antiserum to the 2014/15 northern hemisphere B/Yamagata-lineage trivalent and quadrivalent vaccine virus B/Massachusetts/2/2012. These 52 isolates are antigenically similar to the B/Phuket/3073/2013 virus, the influenza B/Yamagata lineage virus selected for all trivalent and quadrivalent Northern hemisphere influenza vaccines. Genetic characterisation data from viruses isolated from the UK and elsewhere in Europe report a higher percentage of influenza viruses that are distinguishable from the influenza viruses included in the 2014/15 Northern hemisphere influenza vaccine [7, 8]. Effectiveness of the 2014/15 seasonal influenza vaccine in the UK The effectiveness of influenza vaccination in preventing laboratory-confirmed general practice consultations for influenza is estimated annually (at mid-season and end of season) in the UK, using the test negative case control method. This annual study uses sentinel surveillance data provided by the public health agencies in England, Scotland, Northern Ireland and Wales. Results of the United Kingdom 2014/15 end of season analysis indicate that the overall vaccine effectiveness against influenza was 34.3% (95% confidence interval (CI) 17.8% to 47.5%) [8]. Adjusted vaccine effectiveness against influenza A(H3N2) was 29.3% (95% CI 8.6 to 45.3) and against influenza B it was 46.3% (95% CI 13.9 to 66.5). Although vaccine effectiveness was lower during 2014/15 than in previous years, evidence suggests that the vaccine still provided significant protection. The lower estimate of vaccine effectiveness this season likely reflects the circulation of drifted strains of influenza A(H3) and influenza(b), which were not well-matched to the strains contained in the 2014/15 northern hemisphere influenza vaccine. Lower than usual estimates of vaccine effectiveness were also reported in Canada (against medically attended, laboratory confirmed influenza [9] and laboratoryconfirmed influenza-related hospitalisation [10]) and the USA (against laboratory-confirmed influenza associated with medically attended acute respiratory illness [11]). Vaccine mismatch, such as that seen during the 2014/15 season, occurs occasionally. Before 2014/15, strains of influenza contained in the trivalent seasonal influenza vaccine have been well-matched to the dominant circulating types of influenza. Due to the mismatch, the estimate of vaccine effectiveness reported in 2014/15 is lower than vaccine effectiveness estimates that have been reported in previous years. Page 19 of 43

20 Antiviral prescribing rates The GP prescribing rate of oseltamivir (measured using data collected through Audit+ on coded prescriptions in general practice) in Wales followed a similar trend to the sentinel GP consultation rate for ILI. The prescribing rate, per 100,000 practice population, peaked at 3.0 during week (week ending January 12 th, Figure 11), which was one week after the peak for ILI consultations in sentinel practices. The peak in prescribing rate during 2014/15 was higher than in any season since in Wales (Table 2). During the 2014/15 season, globally and in the UK, only small numbers of viruses were detected with reduced sensitivity to oseltamivir or zanamivir [5]. Figure 11. Prescribing rate for oseltamivir per 100,000 practice population in Wales from weeks to week Oseltamivir prescribing rate 23.2 Sentinel GP consultation rate for ILI Rate per 100,000 practice population Antiviral trigger announced Antiviral trigger rescinded Table 2. Peak sentinel GP consultation rates for ILI per 100,000 practice population and peak all Wales prescribing rates per 100,000 for influenza seasons from 2010/11 to 2014/15 Influenza season Peak sentinel GP consultation rate for ILI (per 100,000 practice population) Peak all Wales GP prescribing rate for oseltamivir (per 100,000 practice population) 2010/ / / / / Page 20 of 43

21 Influenza immunisation in Wales 2014/15 Data collection Primary Care data Data on influenza immunisation for the 2014/15 campaign were collected directly from General Practices using the Audit+ Data Quality System. Audit+ interrogates General Practice systems using specified Read codes and automatically relays the relevant anonymous aggregate data to a central database. This provides the information required to monitor uptake of influenza immunisation in Wales, whilst minimising impact on General Practices. Data were collected on immunisations given and recorded on General Practice systems between September 2014 and May 2015 (this report contains data submitted by 5 th May 2015). On a weekly basis throughout 2014/15 data were received from approximately 90% of General Practices in Wales. If data from individual general practices were not received for a particular week, a roll-up exercise was carried out; where the most recent previous submission of data from the relevant general practice was identified and used. This report is based on data submitted from 458 out of 460 practices automatically through Audit+ along with manually extracted data from two practices. The submission rate for 2014/15 through Audit+ was 99.6%. This rose to 100.0% when manual submissions were included. Using Audit+, data were collected on immunisations given to those aged 65 years and older (defined as aged 65 years on 31 March 2014), those aged between six months and 64 years recorded as belonging to one or more clinical risk category (in total and by specific risk category) and children aged two to four years. Uptake data for influenza immunisation during pregnancy include women whose General Practice records contained Read codes associated with pregnancy at any point during September 2014 to January Immunisation uptake figures for pregnant women calculated from General Practice data represent the proportion of women who were recorded as pregnant at any point between September 2014 and January 2015 who had received an influenza vaccine. All data from General Practices were extracted through Audit+ using searches based on the Read codes defined in the PRIMIS Seasonal Influenza Vaccine Uptake Reporting Specification for 2014/15 [12]. Point of delivery survey data of coverage in pregnant women During early February 2015 (one Health Board conducted the survey from 9 to 13 March 2015), Public Health Wales Vaccine Preventable Disease Programme and the Heads of Midwifery and midwife colleagues in all Welsh Health Boards, conducted a survey of how many women delivering in the major maternity units in each Health Board had been offered influenza immunisation and how many had received it [13]. During the five day period information was collected from 431 women giving birth across Wales. This information provides a useful comparison to the uptake data submitted by General Practices, although the uptake measure from the point of delivery survey includes only women whose pregnancies go to full term and the General Practice uptake figures will also include in the denominator women whose pregnancies were not full term and ended before they could be offered vaccination. Year 7 schoolchildren immunisation data Data on uptake of influenza immunisation in the School Year 7 age group were manually submitted by Health Board Immunisation Coordinators on a fortnightly basis throughout the campaign. Uptake figures represent the proportion of all children in school and offered the vaccine who were immunised. The denominator for uptake calculations does not include children in this age group who were not in full time education and the numerator does not include children who were vaccinated in primary care. Page 21 of 43

22 NHS staff immunisation data Immunisation uptake data for NHS staff were provided on a monthly basis from October 2014 to March 2015 by health board occupational health departments. Denominator data were sourced at the start of the campaign, from health boards using Knowledge and Skills Framework (KSF) staff groupings. The approach to offering influenza immunisation to staff not normally considered to have direct patient contact may vary between Health Boards. Data provided relates to immunisations given to all staff and uptake figures presented in this report for staff, with direct patient contact are calculated by aggregating data for staff groups most of which would normally have direct contact with patients. General Practice staff immunisation data An internet-based survey of immunisation uptake in general practices in Wales was conducted by Public Health Wales Vaccine Preventable Disease Programme and Communicable Disease Surveillance Centre, working with the Public Health Wales Informatics Team, in April A link to a Public Health Wales internet site page containing the survey and explanatory information was distributed to all GP Practice Managers in Wales, with a request to participate. The survey enquired about immunisation uptake, by staff group, in each of the practices and also enquired about the number of staff who had declined influenza immunisation. Submitted responses were automatically collated by the Public Health Wales internet site content management system, Cascade, which was provided by the NHS Wales Informatics Service. Data submission rates Data relating to immunisation uptake in patients aged 65y years and older, those at clinical risk and those recorded as being carers were submitted by 100% of general practices in Wales (Tables 1 and 2). This is an increase of 4.9% compared to the 2013/14 season. General Practice data submission rates were 100.0% for all Health Boards. All Health Boards provided uptake data for immunisations given to children in School year seven. All Health Boards in Wales contributed to the point of delivery survey of pregnant women. All Health Boards in Wales provided NHS staff immunisation uptake data. Survey responses were received from 22.5% of general practices in Wales on influenza immunisation uptake among general practice staff. Page 22 of 43

23 Influenza Immunisation uptake Uptake in those aged 65 years and older and those aged six months to 64 years in clinical risk groups Uptake in those aged 65 years and over was 68.0%, a decrease of 0.3 from 68.3% in the 2013/14 season following a five year rising trend (Figure 12). This is below the Welsh Government target of 75%. Ninety per cent of immunisations given to those 65 years and over were delivered by the week ending 13 th January 2015 (Figure 13). Uptake varied by Health Board from 64.9% (Hywel Dda UHB) to 70.1% (Betsi Cadwaladr UHB, Table 3 and Figures 14 and 16) and ranged by Local Authority (LA) from 59.9% (Ceredigion) to 75.2% (Monmouthshire) (Table 3, Figure 14). No Health Board areas achieved the 75% target, however uptake in one LA area (Monmouthshire) exceeded 75%, and in five LAs uptake was above 70% (Table 2). Uptake in those aged six months to 64 years and in a clinical risk group was 49.3%. This is a decrease of 1.8 from 51.1% in the 2013/14 season (Figure 12). Ninety per cent of immunisations given to those aged six months to 64 years in clinical risk groups were delivered by week ending 03 February 2015 (Figure 13). Uptake ranged by Health Board from 44.0% (Abertawe Bro Morgannwg UHB) to 52.9% (Aneurin Bevan UHB, Table 3 and Figures 15 and 17) and by LA from 43.3% (Swansea) to 57.7% (Monmouthshire) (Table 3, Figure 15). According to the data submitted, the proportion of all patients aged six months to 64 years recorded in one or more clinical risk categories was 13.9% (an increase from 13.1% recorded in 2013/14). Figure 12. Trends in seasonal influenza immunisation uptake in patients aged 65 years and over and in those aged six months to 64 years in clinical risk groups, Wales, 2008/ /15. Patients aged 65y and over Patients aged under 65y at risk 59.5% 63.5% 65.7% 67.7% 67.7% 68.3% 68.0% 40.8% 49.1% 48.5% 50.0% 49.7% 51.1% 49.3% Page 23 of 43

24 Figure 13. Uptake of influenza vaccine in patients aged 65 years and over and in those aged six months to 64 years in clinical risk groups, Wales, Uptake (%) y and older uptake y and older uptake m to 64y uptake m to 64y uptake % 0 05/10/ /10/ /10/ /10/ /11/ /11/ /11/ /11/ /11/ /12/ /12/ /12/ /12/ /01/ /01/ /01/ /01/ /02/ /02/ /02/ /02/ /03/ /03/ /03/ /03/ /03/ /04/2015 Week ending Table 3. Trends in uptake of influenza immunisation in Health Boards, Wales, 2012/13 to 2014/15. Uptake in patients aged 65y and older (%) Uptake in patients younger than 65y at risk (%) Practices submitting data (%) Health Board 2012/ / / / / / / / /15 Abertawe Bro Morgannwg UHB Aneurin Bevan UHB Betsi Cadwaladr UHB Cardiff and Vale UHB Cwm Taf UHB Hywel Dda UHB Powys Teaching HB Wales total Page 24 of 43

25 Figure 14. Uptake of influenza immunisation in General Practices during 2014/15, by Health Board, in: (a) patients aged 65 years and over and (b) patients aged six months to 64 years in clinical risk groups. (a) (b) % uptake (0) (2) (3) 0-65 (2) % uptake (0) (0) (0) 0-65 (7) Figure 15. Uptake of influenza immunisation in General Practices during 2014/15, by Local Authority of practice location, in: (a) patients aged 65 years and over and (b) patients aged six months to 64 years in clinical risk groups. (a) (b) % uptake (1) (4) (14) 0-65 (3) % uptake (0) (0) (0) 0-65 (22) Page 25 of 43

26 Figure 16. Uptake of influenza immunisation in Health Boards in Wales in patients aged 65 years and over, 2012/ /15 ranked by uptake in 2014/ / / /2015 Target Uptake (%) Betsi Cadwaladr UHB Aneurin Bevan UHB Cardiff and Vale UHB Wales total Cwm Taf UHB Powys Teaching HB Abertawe Bro Morgannwg Hywel Dda UHB UHB Figure 17. Uptake of influenza immunisation in Health Boards in Wales in patients aged six months to 64 years in clinical risk groups, 2012/ /15 ranked by uptake in 2014/ / / /2015 Target 75 Uptake (%) Aneurin Bevan HB Betsi Cadwaladr UHB Cardiff and Vale UHB Cwm Taf UHB Wales total Powys Teaching HB Hywel Dda UHB Abertawe Bro Morgannwg UHB Page 26 of 43

27 Immunisation uptake by risk group Chronic heart disease or a related condition was recorded in 2.4% of patients aged six months to 64 years, of whom 48.4% were immunised against influenza (Figure 18). Uptake by Health Board ranged from 42.8% (Powys Teaching HB) to 52.7% (Aneurin Bevan UHB, Data table 3). Chronic respiratory disease was recorded in 7.4% of patients aged six months to 64 years, of whom 48.6% were immunised against influenza (Figure 18), ranging by Health Board from 43.7% (Abertawe Bro Morgannwg UHB) to 51.9% (Aneurin Bevan UHB, Data table 3). Chronic kidney disease was recorded in 0.6% of patients aged six months to 64 years, of whom 53.9% were immunised against influenza (Figure 18), ranging by Health Board from 46.9% (Abertawe Bro Morgannwg UHB) to 58.3% (Betsi Cadwaladr UHB, Data table 3). Diabetes was recorded in 3.2% of patients aged six months to 64 years, of whom 64.8% were immunised against influenza (Figure 18), ranging by Health Board from 59.7% (Abertawe Bro Morgannwg UHB) to 68.6% (Cardiff and Vale UHB, Data table 3). Immunosuppression due to disease or treatment was recorded in 0.9% of patients aged six months to 64 years, of whom 58.6% were immunised against influenza (Figure 18), ranging by Health Board from 49.3% (Abertawe Bro Morgannwg UHB) to 62.7% (Betsi Cadwaladr UHB, Data table 3). Chronic liver disease was recorded in 0.3% of patients aged six months to 64 years, of whom 42.0% were immunised against influenza (Figure 18), ranging by Health Board from 37.4% (Abertawe Bro Morgannwg UHB) to 47.6% (Powys Teaching HB, Data table 3). Chronic neurological conditions (including stroke and TIA) were recorded in 1.4% of patients aged six months to 64 years, of whom 46.8% were immunised against influenza (Figure 18), ranging by Health Board from 41.7% (Abertawe Bro Morgannwg UHB) to 49.6% (Aneurin Bevan UHB & Betsi Cadwaladr UHB, Data table 3). In total, there were 24,426 people aged six months to 64 years recorded as being a carer (including carers who are also in a clinical risk group), of whom 53.4% were immunised against influenza (Figure 18). These figures only include those who have identified themselves as a carer to their GP, and have been coded appropriately in the GP records; the true denominator for carers is likely to be higher. Uptake ranged by Health Board from 49.9% (Abertawe Bro Morgannwg UHB) to 59.8% (Cwm Taf UHB, Data table 4). Figure 18. Summary of influenza uptake rates in patients aged 65 years and over and six months to 64 years at risk, by individual risk group, Wales, 2014/ summary data 65y and older Younger than 65y at risk Diabetes Immunosuppression Chronic kidney disease Chronic respiratory disease Chronic heart disease Neurological conditions Chronic liver disease 68.1% 49.3% 64.8% 58.6% 53.9% 48.6% 48.4% 46.8% 42.0% Pregnant women Carers 53.4% 72.4% Page 27 of 43