[Source: European Centre for Disease Prevention and Control (ECDC), full PDF document: (LINK). Extracts, edited.]
Seasonal influenza 2012/13 in Europe (EU/EEA countries) - February 2013
- The 2012/13 seasonal influenza epidemics in Europe started earlier than in 2011/12 (a particularly late and mild season) in western EU/EEA countries and Scandinavia. South-western European countries (Spain and Portugal) have been less affected to date.
- Countries in central and eastern Europe are advised to prepare for a similar pattern of transmission and intensity to that seen in the western Scandinavian countries.
- Overall, there is no clear dominance of any particular influenza viruses. A(H3N2), A(H1N1)* and both lineages of B viruses (Yamagata and Victoria) are all circulating in substantial numbers with different countries reporting different dominant viruses. This differs from what is observed in the United States where influenza A(H3N2) viruses have predominated among the A viruses.
- As one group of influenza B viruses circulating (B Victoria-lineage) has not been included in the current trivalent vaccine, the antigenic match this season between the circulating strains and the vaccine components is imperfect. However, the B Victoria-lineage accounts for only a small proportion of all viruses circulating this season.
- Following replacement of the A(H3N2) component of the 2011/12 vaccine, the vaccine effectiveness of the 2012/-13 influenza vaccine is expected to be higher against influenza A(H3) infection than the especially low levels observed in Europe for the 2011/12 season. First indications from the UK confirm this although the estimates are in the range of 45% to 55%.
- Informal reports suggest that national seasonal influenza vaccine coverage is similar to last season, although the VENICE data show there have been some small declines in coverage in older people in a number of countries since 2009.
- There were some indications that pressure on primary care and emergency room services in the first affected countries was higher than during the equivalent period of the 2011/12 epidemic. However, this increased pressure maybe partly due to the fact that the epidemics started before the Christmas and New Year holidays when primary care services scale down in some countries.
- There are some indications of local pressures on secondary healthcare services and intensive care units in some areas justifying preparation for surge capacity, but these are not strong enough to support putting hospital services on general alert.
- To date only one oseltamivir-resistant A(H1N1) virus with the H275Y mutation has been reported. It was detected in the Netherlands in an immuno-compromised patient after treatment with oseltamivir. All other viruses tested have been susceptible to the neuraminidase inhibitors. All screened influenza A viruses are resistant to adamantanes and there is no basis for the use of these drugs.
- There is some indication of excess mortality from all causes in older people in some countries in temporal association with influenza epidemics. This applies especially in Denmark where influenza A(H3N2) virus is dominant. It is too early to determine whether this excess mortality is associated with cold weather, influenza virus infection or other causes.
- In the UK in recent weeks, there has been an apparent rise in the number of cases of severe pneumonia due to toxin-producing strains of Staphylococcus aureus (PVL-SA), possibly associated with influenza. It remains to be seen whether this phenomenon will occur in other EU countries. Health practitioners should therefore be vigilant and clinicians are encouraged to report cases to their national authorities.
- There are no concerns over the safety of seasonal influenza vaccines in use this season.
- The main uncertainties are the impact that the substantial circulation of influenza A(H1N1) will have among younger patients, especially as regards the severity of disease, and if and how circulating B Victoria-lineage viruses might affect vaccine effectiveness.
ECDC’s scientific and public health advice
It should be remembered that influenza can cause severe disease and death, especially in older patients and patients with underlying conditions and this is being seen from hospital surveillance this season. Even young healthy persons are at some risk of experiencing severe disease.
The scientific and public health data support an emphasis on traditional methods of reducing transmission: respiratory hygiene, regular hand-washing and early self-isolation when ill.
In view of the continued circulation of influenza viruses in Europe, countries still experiencing significant transmission should continue to offer seasonal vaccines to those recommended by national authorities. VENICE* surveys have indicated that the most commonly recommended groups are older people, those with chronic disease, healthcare workers and (in many but not all countries) pregnant women. Vaccination remains the most effective single method of protecting people against influenza.
Influenza A(H3N2) outbreaks in nursing homes for older people and among those with chronic illness were observed during the late stages of the previous season in some of the first affected countries. Immunisation of both staff and patients is recommended if that has not been done already.
Neuraminidase inhibitors should be used, as prophylaxis or early treatment, according to national guidance, especially in outbreaks among vulnerable groups such as in care homes.
Epidemiology and impact on primary healthcare services
The 2012/13 season started around week 49/2012 and influenza activity has been increasing since then. During week 3/2013, 14 of 26 countries reporting clinical data stated that they were experiencing medium or high intensity of influenza activity.
In weeks 52/2012, 1/2013, 2/2013 and 3/2013, geographical spread of influenza activity was reported as regional or widespread by 7, 13, 15 and 16 countries, respectively, mainly in western and northern Europe (with the exception of Portugal and Spain) (see Maps 1–3). In week 3/2013, many countries were still reporting rising trends of ILI or ARI. The majority of the 13 countries which returned the questionnaire mentioned that it was too early to estimate any particular pressure on primary healthcare services. Some noted that the epidemics had started before the Christmas and New Year holidays, putting pressures on emergency rooms that were operating at reduced capacity over the holiday period.
In the majority of countries, the most affected age group as reported from primary care services has been 0–4 year-olds, even though in Belgium, Iceland, Ireland, Malta and Norway, rates of influenza-like illness and acute respiratory infection (ILI/ARI) have been higher among 15–64 year-olds. In all countries but Iceland and parts of the UK (Northern Ireland and Scotland), a lower incidence of cases with mild illness seeking primary care was observed in the older age groups (>64 years old). This is the distribution of care-seeking by age group that is typically observed and may not necessarily represent the incidence of infection and disease. From the questionnaire, Denmark reported much higher percentages of ILI consultation in the Capital region putting pressure on the on-call service over Christmas compared with other regions.
The respiratory syncytial virus (RSV) activity had already peaked in week 51/2012 and has continuously declined since then. RSV may have contributed to an observed increase in respiratory symptoms, especially in children.
Epidemiology and impact on secondary healthcare services
Countries reporting severe influenza surveillance data have applied case definitions for laboratory-confirmed influenza requiring hospitalisation or severe acute respiratory infection sometimes without laboratory confirmation. For the purpose of this report, and following the reporting preference of most EU/EEA countries, only those reporting laboratory-confirmed hospitalised influenza were included in the analysis.
From week 40/2012 to week 3/2013, 593 laboratory-confirmed hospitalised influenza cases were reported by eight countries (Belgium, France, Ireland, Romania, Slovakia, Spain, Sweden and the UK). Of these cases, 320 (54%) tested positive for influenza type A and 273 (46%) for type B. Of 162 subtyped influenza A viruses, 91 (56%) were A(H1) and 71 (44%) were A(H3) viruses.
The male-to-female ratio was 1:1. Of 273 cases with reported age, 92 (34%) were in the 45–64 year-old group (Figure 1). This distribution differs from the one observed in the 2011/12 season where the largest proportion of cases had been in the youngest and oldest age groups and A(H3) had dominated.
Of the 226 hospitalised influenza cases with known outcome, 18 died; giving a hospitalised case–fatality rate of 8%. Out of the 18 cases with a fatal outcome, one was reported with influenza A(H3), seven with influenza A with an unknown subtype, six with influenza A(H1), and four with influenza B virus. The median age of the 18 fatal cases was 60 years (range: 3–102 years).
Of 164 hospitalised laboratory-confirmed influenza cases with information on underlying conditions, 69 (42%) had at least one recognised risk factor for severe disease, most commonly obesity (18/69). Five cases were pregnant women, which is about 3% of the cases with known underlying conditions.
Of 122 cases with known vaccination status, 113 (93%) were reported as not vaccinated.
In Belgium, paediatric surveillance of influenza activity started when RSV was still present, while in the previous season, the epidemics were dissociated. This may have had a significant impact on the perception of paediatricians. Many more respiratory samples were collected from hospitals than last season, at the same period of the epidemic (i.e. week 1/2013). So far, in 29 confirmed cases, no ICU admission, no critical state on admission, no acute respiratory distress syndrome and only one fatality in a very old patient (102 years old) with co-morbidities were noted. The age distribution of severe influenza cases is similar to the last season.
In the Czech Republic, up to the end of week 1/2013, a cumulative total of 33 severe-illness patients with laboratory-confirmed influenza A(H1N1) or influenza A (not subtyped), including four deaths, were reported by intensive and resuscitation care units. These high numbers of severe influenza caused a similar pressure as in the two previous years.
In Denmark, some regions reported more hospitalisations in press releases than in previous years, but according to the national surveillance system of ICU admissions due to influenza, there are fewer cases than in the two previous seasons. However, the burden of influenza among the elderly seems to be higher this season.
In France, the mean age of laboratory-confirmed influenza patients admitted to ICU is lower than the previous season (34 years versus 51).
In Ireland, more influenza B cases have been observed this season, but no further details on the impact or the virus lineage are available as yet.
In Spain, only 29 severe hospitalised cases have been reported up to week 3/2012, compared to 65 cases during a similar period in the previous season. Of these cases, 70% were influenza B virus and their median age was 35 years (IQR: 5–55), which is comparable to the median age among severe hospitalised influenza B cases in the season 2011/12 (30; IQR: 3–61).
In the UK (England), a surveillance system with comparable data for both hospital admissions and ICU admissions was established in 2011/12, but reporting through similar systems in 2010/11 showed larger pressures. Chronic respiratory conditions are to date the most frequently reported underlying clinical risk factor in 2012/13 for ICU admissions reported through the sentinel network. There has been an apparent rise in Panton–Valentine leukocidin (PVL) pneumonia cases and possible association with influenza. PVL cytotoxin-producing strains of Staphylococcus aureus (PVL-SA) typically cause skin and soft tissue infections. They can sometimes cause more severe invasive infections and the association with severe community-acquired pneumonia (CAP) is recognised with high (50–75%) mortality rates reported. Over the four–week period 6 December 2012 to 7 January 2013, the national UK reference laboratory confirmed 18 cases of severe CAP caused by PVL-SA; all have been admitted to intensive care units and four (22%) have died. This compares to a national figure of 30–40 PVL-CAP cases per year across England, usually peaking in the winter months. Fourteen have been due to meticillin-sensitive S. aureus infection and four due to meticillin-resistant S. aureus, associated with a variety of strains. Most cases have reported an influenza-like prodrome with at least six confirmed with an influenza B co-infection. Influenza has been circulating in the community in England, with the dominant strain being influenza B. Cases have been distributed around the country with at least two small household clusters identified. Patients were aged from four to 63 years (median 41 years) and 11 (61%) were female. Further epidemiological and microbiological work is underway*.
The UK (Scotland) has reported 20 ICU cases of confirmed seasonal influenza despite only being a few weeks into the season. During the previous season, 17 cases were admitted to ICU in total. However, there are no reports of any severe pressure on general admission to hospitals. Geographically, these ICU cases are representative of the population distribution. So far, there have been three deaths among the 20 ICU cases (two with influenza A(H3N2) and one with influenza A, not subtyped). The mean age is lower than for the previous season (45 years versus 62). RSV co-infection in an infant and an invasive group A streptococcal infection in an adult ICU case who died have been documented. An increase in the number of invasive meningococcal infections or invasive group A streptococcal infections has been noticed in those geographical areas in which cases of influenza are being reported.
Circulating viruses from sentinel sources
Of the 2 948 influenza virus detections in sentinel specimens from week 40/2012 to week 3/2013, 1 430 (48.5%) were type A, and 1 518 (51.5%) were type B viruses. Of 1 253 influenza A viruses subtyped, 732 (58%) were A(H1) and 521 (42%) were A(H3), showing the return of A(H1N1) which hardly circulated in Europe last season. Of the 269 type B viruses ascribed to a lineage, 231 (86%) were Yamagata and 38 (14%) were Victoria. The latter lineage is not included in the 2012/13 vaccine. 
Circulating viruses from non-sentinel sources
Of the 11 719 influenza viruses detected from non-sentinel sources from week 40/2012 to week 3/2013, 8 440 (72%) were type A, and 3 279 (28%) were type B. Of 4 368 type A viruses subtyped, 3 110 (71%) were A(H1) and 1 258 (29%) were A(H3). Of the 456 B viruses ascribed to a lineage, 412 (90%) were Yamagata and 44 (10%) were Victoria. The higher proportion of influenza A viruses is not surprising, as non-sentinel specimens are collected for diagnostic purposes, e.g. in hospitals, suggesting that specimens were taken from more severe cases. 
Antigenic and genetic characteristics
From week 40/2012 to week 3/2013, 168 antigenic characterisations of influenza viruses from sentinel and non-sentinel specimens were reported: the majority (92) have been characterised as A(H3)/Victoria/361/2011-like, 16 as A(H1) A/California/7/2009 (H1N1)-like, 42 as B/Wisconsin/1/2010-like (B/Yamagata/16/88-lineage), one as B/Florida/4/2006-like (B/Yamagata/16/88 lineage), 13 as B/Brisbane /60/2008-like (B/Victoria/2/87 lineage) and three strains have not been attributed to any category. 
Of the 143 genetic characterisations of influenza viruses reported for sentinel and non-sentinel specimens from week 40/2012 to week 3/2013, 58 were A(H3) clade representative A/Victoria/208/2009 and fell in groups 3A, 3C and 5; 40 were A(H1) from groups 6 and 7; 18 were B(Yam)-lineage clade representing B/Estonia/55669/2011; 12 were B(Yam)-lineage clade representing B/Wisconsin/1/2010; 11 were B(Vic) lineage clade representing B/Brisbane/60/2008 and three strains were not attributed to any clade/group. 
Susceptibility to antivirals
From week 40/2012 to week 3/2013, 196 influenza A and B viruses from Denmark, Germany, the Netherlands, Norway, Spain, Sweden and the UK have been tested for neuraminidase inhibitor (oseltamivir and zanamivir) susceptibility and none showed genetic (markers) or phenotypic (IC50) evidence for (highly) reduced inhibition. All 19 influenza A viruses screened for M2-blocker susceptibility were resistant. Recently in the Netherlands, an oseltamivir-resistant A(H1N1) virus with the H275Y amino acid substitution was detected in a hospitalised immuno-compromised patient. This resistant variant emerged during oseltamivir therapy and was detected shortly after oseltamivir was stopped and before zanamivir therapy was started. The patient was also treated with antibiotics for pneumonia due to Haemophilus influenzae, improved rapidly and was discharged 20 days after onset of respiratory symptoms (A. Meijer, personal communication). Hence it remains the case that no oseltamivir-resistant infections have been found to be circulating in Europe. 
Susceptibility – seroepidemiology
As in previous years, the only country undertaking an early annual seroepidemiological survey was Norway. In contrast to the two previous years, no particular virus type or subtype could be identified as likely to predominate this season . With respect to age distribution, the results are highly compatible with the age-specific incidence of laboratory-confirmed influenza in Norway with lower incidence in the 5–24 year age group for A(H1N1), in the 0–24 year-olds for A(H3N2), and in the 15–24 year-olds for Yamagata-lineage influenza B. The apparently good immunity in the 5–24 year-olds against A(H1N1) is corroborated by the relatively few numbers of laboratory-confirmed cases in this age group in Norway. Even so, Norway experienced a significant incidence of influenza in weeks 1 and 2/2013, with A(H1N1) as the predominant virus. The Norwegian reporter commented that other age groups (e.g. infants and/or adults above 25) may play a larger role in the spread of this virus than commonly thought. There have been deaths, including in younger persons, associated with A(H1N1) in Norway this season and in the Czech Republic.
Seasonal vaccine coverage data are not yet available from the VENICE project* for the 2012/13 season. From the questionnaire, Latvia reported a lower proportion of people vaccinated while the UK (England) reported vaccination coverage comparable to 2011/12. Preliminary results from England estimate an uptake of >70% among those aged ≥65 years and around 50% in those under 65 years old in a clinical risk group, with a much higher uptake among pregnant women than during the previous season. Among the nursing homes affected by ARI outbreaks in France, the vaccine coverage (81%) was the lowest observed since 2003/04. This proportion is still to be confirmed, but it could reflect a lower national vaccine coverage among older people this season. The UK (Scotland) reported an increased uptake by pregnant women; 48.3% in those without risk factors and 64.6% in those with risk factors. Norway mentioned low vaccination coverage in risk groups. There is no information on immunisation of healthcare workers. Overall, it should be noted that there have been small declines in vaccine coverage in older age groups (the only risk group with consistent data) in a number of EU countries since the 2007/08 season .
Match between circulating and vaccine strains
Notwithstanding the absence of influenza B Victoria lineage from the composition of the vaccine , the remaining viruses circulating this season seem to be well-matched with the components of the 2012/13 seasonal vaccine viruses. Nevertheless, this match does not necessarily mean that the vaccine effectiveness is as high as would be desirable [9,10].
Characterisation of A(H3N2) viruses collected in Denmark, Germany, Norway, Sweden and the UK (England) from 1 September to 31 December 2012 have shown antigenic similarity to the vaccine strain A/Victoria/361/2011. A(H1N1) viruses continued to show genetic drift from the vaccine virus A/California/07/2009, but the vast majority remained antigenically similar .
A recent American study  published an early estimate of influenza vaccine effectiveness non-adjusted for age of 62% (95% CI: 51%–71%) for 2012/13 which is better than for the previous season in the United States. A study from Canada showed somewhat lower levels . However, it is essential to note that the US estimates were not adjusted for age, risk groups and other confounders and the proportions of circulating viruses in the USA and the EU are quite different this season: there are few A(H1N1) viruses circulating in the USA. Also, the analytic approach is different; in Europe the focus is more on effectiveness in the high risk groups. Hence, the US percentage should be interpreted with caution and may not reflect the vaccine effectiveness in Europe or for high risk groups. Early estimates of vaccine effectiveness in the UK have shown an overall adjusted vaccine effectiveness of 51% (CI: 27%–68%) with 49% against influenza A alone and 52% against influenza B . Further results from the I-MOVE consortium are expected in the coming weeks.
In France, none of the 24 cases admitted to ICU had been vaccinated.
In the UK (Scotland), an ICU case had been infected by an influenza B Victoria-lineage not included in the trivalent vaccine. There have been a further three recent vaccine failures in ICU cases – all influenza A infections (results from detailed molecular testing are awaited).
A number of countries undertake their own monitoring of death statistics. In addition, all-cause mortality by age group in 16 EU/EEA countries is monitored in a timely manner by the EUROMOMO* project, using a common algorithm to standardise excess mortality estimates across Europe. Monitoring early mortality data is useful for detecting the impact on mortality of unusual severe events like influenza epidemics, heatwaves or cold weather.
Pooled analysis for week 3/2013  does not show any excess of all-cause mortality so far this season. However, two of the 16 reporting countries, Denmark and the UK (Scotland & England) saw increased mortality in people 65 years of age and above. The increase was particularly evident in Denmark, where influenza A(H3N2) transmission is predominant and peaked around Christmas.
Due to reporting delays, excess mortality associated with influenza may also appear after an interval. It has been estimated that there may be up to 38 500 premature deaths in the EU/EEA associated with influenza in a single influenza season .
Situation in other temperate countries in the northern hemisphere 
In Canada, some regions have reported widespread and localised influenza activity and 107 additional influenza outbreaks have been reported. Influenza virus detections by type/subtype to date have been as follows: 97.5% influenza A (33.2% A(H3), 1.2% A(H1N1) and 65.6% A(not subtyped)) and 2.5% influenza B. 
In the United States, influenza activity has remained elevated, but may have peaked in some regions. The virological pattern has been considerably different to that in Europe as there have been very few influenza A(H1N1) viruses. The proportions of influenza A and B viruses have been 80% and 20%, respectively. Among subtyped influenza A viruses, the proportion of A(H1N1) has been 1%. 
In China, influenza activity has remained at a low level in the south but has continued to increase in the north. The distribution of circulating viruses has been 82% to 99% of influenza A and 1% to 18% of influenza B. Among subtyped influenza A viruses, 67% to 75% have been A(H3N2) and 15% to 18% have been A(H1N1) viruses. No resistance to neuraminidase inhibitors has been observed. 
In Japan, A(H3) virus has largely dominated, followed by a few B(Victoria lineage) and some A(H1N1) viruses .
In summary, the intensity of influenza activity in northern hemisphere countries outside Europe is high, but heterogeneous. Similar to the previous season in the EU/EEA, the proportion of A(H1N1) is very low in North America and Japan. It is higher in China, but not dominant.
Except in some areas of North America, there are no clear indications of particular impact (stress) on healthcare services or other essential services this season.
Situation in the temperate countries of the southern hemisphere in the 2012 season [16,21]
In Australia there were very few notifications of influenza A(H1N1). Influenza A(H3N2) was the predominant circulating virus, along with increasing co-circulation of influenza B. 
Of 2 330 detected influenza viruses in New Zealand with known subtype or lineage, 1 526 (65%) were influenza A(H3N2), 244 (10%) A(H1N1), 252 (11%) B (Victoria-lineage) and 69 (3%) B (Yamagata-lineage). 
In South Africa 116 A(H3N2) viruses, 1 A(H1N1) virus and 115 B viruses were detected. 
The influenza A(H3N2) virus was predominant in Chile and Uruguay, while in Paraguay and Argentina transmission was essentially associated with A(H1N1). Few influenza B were detected. 
Influenza A(H1N1) was dominant in Brazil with fewer A(H3) and B viruses. Towards the end of the season, A(H3) became dominant. 
The intensity of reported influenza-like illness was similar to the previous season in almost all countries of the southern hemisphere.
Implications for Europe
The virological influenza pattern observed on other continents was not consistent enough to make a clear prediction for the 2012/13 season in Europe. However, in general, the findings on the impact of influenza in the southern hemisphere in 2012 are reassuring. The match of the A(H3N2) viruses with the vaccine was considered good and there was no evidence of resistance to neuraminidase inhibitors.
Safety of interventions in Europe
In the trivalent Novartis vaccine, flocculation was observed which was not considered unsafe, but was responsible for a limited shortage. Other than that, there were no indications of any new adverse event following immunisation (AEFI) safety signals related to the 2012/13 trivalent seasonal influenza vaccines being used in the EU. Likewise, no convincing adverse event signals have been reported for the neuraminidase inhibitors, the antivirals used the most in Europe .
ECDC’s scientific and public health advice
Simple protective measures
While the scientific base on effectiveness for measures like early self-isolation, hand-washing and good respiratory hygiene is not that strong for influenza, such evidence that exists supports a recommendation of these simple measures.
Many people for whom influenza vaccination is recommended by their national health authorities are still unvaccinated. Although it is late for immunisation, it is advantageous to immunise these risk groups, especially in countries where transmission is not yet declining in a convincing manner . After the replacement of the A(H3N2) strain, vaccine effectiveness is somewhat higher this season than last . Vaccination is recommended by Member States for older people, those in medical risk groups and for healthcare workers. The majority of countries also recommend immunising pregnant women. Vaccination remains the most effective single way of protecting individuals and their families against influenza infection and disease, but more effective vaccines are needed .
Notwithstanding controversies over interpretation and re-analysis of historic trials against different earlier influenza viruses, the available data on balance continue to support the early use of antiviral treatment in all those presenting with severe influenza-like illness pending virological confirmation, in those with risk factors with milder disease and those in risk groups and thought to have been exposed [29,30]. This has been confirmed by recent observational analyses of effectiveness against influenza A(H1N1) which now accounts for a sizeable proportion of the seasonal viruses in Europe. This season, no reduced antiviral susceptibility or resistance has been detected in screened circulating strains, unless one oseltamivir-resistant strain in an immuno-compromised patient treated with oseltamivir was very recently detected in the Netherlands. The evidence suggests that older people and especially those in residential care will especially benefit from early antiviral treatment or prophylaxis, even immunised persons when outbreaks occur in those settings [29–31].
The early experience from western Europe indicates that there is only limited reason to alert hospital services of potentially increased numbers of influenza patients needing hospital/intensive care in the next few weeks. This may, however, not be the case in countries were A(H1N1) predominates and vaccine coverage in risk groups is low.
With the return of A(H1N1), the mean age of patients, compared to previous seasons, will probably decrease in affected countries, but classical underlying conditions and old age remain the main risk factors for severe influenza disease, particularly due to A(H3N2) infection.
Outbreaks in nursing homes for older people and those with chronic illness were reported last season. This supports prevention through immunisation and/or prophylactic use of antivirals in patients and in particular in staff, if that has not been done already, and treatment of outbreaks of influenza-like illness with antivirals [31–33].
The 2012/13 season started early, being most apparent in north-western Europe with a suggestion of the west-to-east geographic progression seen in earlier years. This may allow non-affected countries, especially in central and eastern Europe, to be better prepared.
The single available sero-survey (Norway) suggests that a wide range of viruses is likely to circulate, but it is difficult to anticipate what will happen in other countries as Norway had a very high coverage with A(H1N1) monovalent vaccine.
While there are some indications of particular pressures in ICUs in some countries, the pattern is heterogeneous, making it difficult to estimate the possible workload for ICUs in individual countries.
With the replacement of the A(H3N2) component, the effectiveness of the 2012/13 vaccines among risk groups is somewhat better than in the 2011/12 season, but further vaccine effectiveness studies, such as I-MOVE* field effectiveness studies using the ECDC-developed standard protocols, are needed to confirm this hypothesis.
- WHO Report of the Review Committee on the Functioning of the International Health Regulations (2005) and on Pandemic Influenza A (H1N1) 2009 (Fineberg Report) Final submitted to the World Health Assembly 2011 http://apps.who.int/gb/ebwha/pdf_files/WHA64/A64_10-en.pdf
- Nicoll A, Ammon A, Amato Gauci A, Ciancio B, Zucs P, Devaux I, Plata F, Mazick A, Mølbak K , Asikainen T, Kramarz P. Experience and lessons from surveillance and studies of the 2009 pandemic in Europe. Public Health 2010 124:14–23.
- Nicoll A Planning for uncertainty: a European approach to informing responses to the severity of influenza epidemics and pandemics Bulletin of the World Health Organization 2011;89:542-544. doi: 10.2471/BLT.11.089508 http://www.who.int/bulletin/volumes/89/7/11-089508/en/index.html
- Reed C, Biggerstaff M, Finelli L, Koonin LM, Beauvais D, Uzicanin A, et al. Novel framework for assessing epidemiologic effect of influenza epidemics and pandemics. Emerg Infect Dis 2013; 19(1): 85-91.
- European Centre for Disease Prevention and Control. Weekly influenza surveillance overview. 25 January 2013. Stockholm: ECDC;2013. Available from http://ecdc.europa.eu/en/publications/Publications/Forms/ECDC_DispForm.aspx?ID=1042
- Norwegian Institute of Public Health Rapport om scenarioer for influensaepidemi i 2013, 2 Januar 2013. Folkehelseinstituttet Jan 2012. (Norway) accessible to http://www.fhi.no/dokumenter/a74a08b952.pdf
- Seasonal influenza vaccination in EU/EEA, influenza season 2010-11. VENICE II consortium. Available from http://venice.cineca.org/Final_Seasonal_Influenza_2010-11.pdf
- WHO Recommended composition of influenza virus vaccines for use in the 2012–2013 northern hemisphere influenza season Report of strain selection meeting February 2012. http://www.who.int/influenza/vaccines/virus/recommendations/201202_recommendation.pdf
- Early Estimates of Seasonal Influenza Vaccine Effectiveness — United States, January 2013. MMWR 2013 accessible at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6202a4.htm?s_cid=mm6202a4_w
- Nicoll A, Sprenger M. Low effectiveness undermines promotion of seasonal influenza vaccine. Lancet 2013; 13: 7-9
- CNRL report, December 2012. accessible at http://www.ecdc.europa.eu/en/publications/Publications/influenza-virus-characterisation-CNRL-dec-2012.pdf
- Skowronski DM, Janjua NZ, De Serres G, Dickinson JA, Winter A, Mahmud SM, Sabaiduc S, Gubbay JB, Charest H, Petric M, Fonseca K, Van Caeseele P, Kwindt TL, Krajden M, Eshaghi A, Li Y. Interim estimates of influenza vaccine effectiveness in 2012/13 from Canada’s sentinel surveillance network, January 2013. Euro Surveill. 2013;18(5):pii=20394. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20394
- McMenamin, 2013 McMenamin J, Andrews N, Robertson C, Fleming DM, Durnall H, von Wissmann B, Ellis J, Lackenby A, Cottrell S, Smyth B, Zambon M, Moore C, Watson JM, Pebody RG. Effectiveness of seasonal 2012/13 vaccine in preventing laboratory-confirmed influenza infection in primary care in the United Kingdom: mid-season analysis 2012/13. Euro Surveill. 2013;18(5):pii=20393. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20393
- EuroMOMO. European mortality bulletin week 4, 2013. Available from http://www.euromomo.eu/results/pooled.html
- Nicoll A, Ciancio BC, Lopez Chavarrias V, Mølbak K, Pebody R, Pedzinski B, Penttinen P, van der Sande M, Snacken R, Van Kerkhove MD. Influenza-related deaths - available methods for estimating numbers and detecting patterns for seasonal and pandemic influenza in Europe . Euro Surveill. 2012;17(18):pii=20162. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20162
- World Health Organization. Influenza Update No 178. 31 January 2013. Available from http://www.who.int/influenza/surveillance_monitoring/updates/2013_02_01_surveillance_update_178.pdf
- Public Health Agency of Canada. Fluwatch. December 30, 2012 to January 5, 2013 (Week 01). Available from http://www.phac-aspc.gc.ca/fluwatch/12-13/w01_13/pdf/fw2013-01-eng.pdf
- Centers for Disease Control and Prevention. FluView. 2012-2013 Influenza Season Week 52 ending December 29, 2012 [internet]. Available from http://www.cdc.gov/flu/weekly/weeklyarchives2012-2013/weekly52.htm
- Chinese National Influenza Center. Chinese weekly influenza surveillance report. Week 52 2012 [internet]. Available from http://www.cnic.org.cn/eng/show.php?contentid=624
- Infectious Agents Surveillance Report [Japan]. Weekly reports of influenza virus isolation/detection, 2008/09 - 2012/13. Available from https://nesid3g.mhlw.go.jp/Byogentai/Pdf/data2e.pdf
- World Health Organization. Review of the 2012 winter influenza season, southern hemisphere. WER 2012; 44 (87) 421-36.
- Australian Government. Department of Health and Ageing. Australian influenza report 2012—29 September to 12 October 2012 (#10/2012) [internet]. Available from http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm
- Public Health Surveillance [New Zealand]. Influenza Weekly Update 2012/39: 24 – 30 September 2012. Available from http://www.surv.esr.cri.nz/PDF_surveillance/Virology/FluWeekRpt/2012/FluWeekRpt201239.pdf
- National Institute for Communicable Diseases [South Africa]. Influenza surveillance report - South Africa [internet]. Available from http://www.nicd.ac.za/?page=seasonal_influenza&id=72
- Boletim Informativo de Influenza: Semana Epidemiológica 44. [internet]. Available from http://portalsaude.saude.gov.br/portalsaude/noticia/8100/785/boletim-informativo-de-influenza:-semana-epidemiologica-44.html
- European Medicines Agency. Pandemic influenza pharmacovigilance safety updates. Available from: http://www.ema.europa.eu/ema/index.jsp?curl=pages/special_topics/general/general_content_000246.jsp&murl=menus/special_topics/special_topics.jsp&mid=WC0b01ac058004bf57
- Mereckiene J, Cotter S, D'Ancona F, Giambi C, Nicoll A, Lévy-Bruhl D, Lopalco PL, Weber JT, Johansen K, Dematte L, Salmaso S, Stefanoff P, Greco D, Dorleans F, Polkowska A, O’Flanagan D, on behalf of the VENICE project gatekeepers group. Differences in national influenza vaccination policies across the European Union, Norway and Iceland 2008-2009 . Euro Surveill. 2010;15(44):pii=19700. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19700
- Kissling E, Kissling E, Valenciano M, Larrauri A, Oroszi B, Cohen JM, Nunes B, Pitigoi D, Rizzo C, Rebolledo J, Paradowska-Stankiewicz I, Jiménez-Jorge S, Horváth JK, Daviaud I, Guiomar R, Necula G, Bella A, O’Donnell J, Głuchowska M, Ciancio BC, Nicoll A, Moren A. Low and decreasing vaccine effectiveness against influenza A(H3) in 2011/12 among vaccination target groups in Europe: results from the I-MOVE multicentre case–control study. Euro Surveill. 2013;18(5):pii=20390. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20390
- Moscona A. Neuraminidase inhibitors for influenza. N Engl J Med. 2005;353:1363-1373
- Hernan MA and Lipsitch M Oseltamivir and Risk of Lower Respiratory Tract Complications in Patients With Flu Symptoms: A Meta-analysis of Eleven Randomized Clinical Trials Clin. Infect. Diseases; first published online: June 15, 2011 http://cid.oxfordjournals.org/content/early/2011/06/14/cid.cir400.full
- Muthuri SG, Myles PJ, Venkatesan S, Leonardi-Bee J, Nguyen-Van-Tam J. Impact of neuraminidase inhibitor treatment on outcomes of public health importance during the 2009-10 influenza A (H1N1) pandemic: a systematic review and meta-analysis in hospitalised patients. J Infect Dis 2012. doi: 10.1093/infdis/jis726
- Hayward, A.C., et al., Effectiveness of an influenza vaccine programme for care home staff to prevent death, morbidity, and health service use among residents: cluster randomised controlled trial. BMJ, 2006. 333(7581): 1241 Citation BMJ, doi:10.1136/bmj.39010.581354.55 (published 1 December 2006)
- Hayward AC, Watson J Effectiveness of influenza vaccination of staff on morbidity, and mortality of residents of long term care facilities for the elderly. 2011 Mar 16;29(13):2357-8. Epub 2011 Feb 2.
* Throughout this document ‘A(H1N1)’ refers to the pandemic 2009 virus strain officially designated A(H1N1)pdm09. This is now one of the circulating seasonal influenza viruses.
* For further information, see http://www.hpa.org.uk/hpr/news/#pvlsa and for clinical guidance see http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1267551719486 and http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1218699411960
* Vaccine European New Integrated Collaboration Effort. http://venice.cineca.org/
* The European Mortality Monitoring Project. http://www.euromomo.eu/