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ECDC FORWARD LOOK RISK ASSESSMENT - Likely scenarios for influenza in 2010 and the 2010/2011 influenza season in Europe and the consequent work priorities (ECDC, excerpts, edited)
ECDC FORWARD LOOK RISK ASSESSMENT - Likely scenarios for influenza in 2010 and the 2010/2011 influenza season in Europe and the consequent work priorities (ECDC, excerpts, edited)
[Source Full PDF Document, European Centre for Diseases Prevention andControl (ECDC), March 8, 2010: LINK. EDITED.]
ECDC FORWARD LOOK RISK ASSESSMENT - Likely scenarios for influenza in 2010 and the 2010/2011 influenza season in Europe and the consequent work priorities
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Executive summary
Work has been undertaken by ECDC with substantial input from its Advisory Forum, other European experts and WHO in order to inform EU stakeholders as to the likely scenarios for influenza transmission (pandemic and inter-pandemic) in Europe in the immediate future.
Specifically, this work has been looking at what can most reasonably be expected in the first half of 2010 and to the end of the 2010/11 influenza season. It has also identified the further information that needs to be gathered through surveillance and research in order to determine vaccine strategies, including implementation of the new EU Health Council Recommendation on seasonal influenza immunisation.
Evidence, data and information were considered from a number of sources including prior pandemics, the European experience during this pandemic, sero-epidemiology, modelling and especially what happened in the Southern Hemisphere in 2009/10 following their initial autumn/winter wave.
On the basis of this it seems unlikely that there will be another spring/summer pandemic wave in Europe unless there are significant unrecognised uninfected populations or the virus changes and becomes more transmissible.
Serological surveys (measuring the levels of immunity in the community) could help reduce this uncertainty.
However, only a limited number of Member States are currently using this tool to assess susceptibility. Other important data and analyses are lacking and hence priority work has been identified for Member States and ECDC to undertake, especially to inform vaccination strategies using the currently authorised monovalent pandemic vaccines and the anticipated 2010/2011 seasonal trivalent influenza vaccines (which will include the pandemic H1N1 strain).
It seems highly likely that even when WHO judges the post-peak and post-pandemic phases to have been reached, Europe will continue to experience low-level transmission and small outbreaks of the pandemic 2009 A(H1N1) influenza. This is the most likely scenario throughout the whole of 2010. However, larger outbreaks cannot be excluded given the lack of information from seroepidemiology.
Epidemic transmission of the pandemic virus is highly likely in the next (2010/2011) winter season, at least in very young children and other susceptible individuals. It is also most likely that pandemic influenza A(H1N1) will become the dominant virus in the coming winter season along with influenza B viruses, though the presence of influenza A(H3N2) viruses as well cannot presently be excluded. By then Europe will probably be referring to this combination as the ?new seasonal influenza?.
There is currently no evidence of a changed pathogenicity of the circulating pandemic influenza virus.
No significant genetic or antigenic changes to the pandemic influenza virus have so far been reported and so patterns in morbidity and mortality similar to those seen during the pandemic should initially be expected from this virus next winter though numbers of cases will be considerably smaller because of the previous transmission and vaccination.
In summary, the implications for vaccination strategies from this conservative forward look is that transmission of the pandemic virus will continue through 2010 albeit at low levels, and that this will be the predominant influenza A virus causing seasonal influenza in the winter of 2010/2011. At present the currently authorised monovalent pandemic vaccines and the new 2010/2011 seasonal influenza vaccines are likely to be effective against the 2009 A(H1N1) strain for the coming 6?10 months. Therefore, for Member States wishing to protect unimmunised citizens in the spring of 2010 and autumn/winter of 2010?2011, there will be advantages to continuing to offer these vaccines (or trivalent vaccines with the pandemic antigen when they are available) to their chosen risk and target groups. ECDC?s advice to EU citizens remains to accept influenza vaccination when it is offered to them.
Influenza viruses are notorious for their unpredictability and so this forward look risk assessment must not be seen as representing anything more than the most likely scenario. It will also be updated as relevant and significant data become available.
There are a number of uncertainties about the new seasonal influenza that Europe will face in the winter of 2010/11 concerning the burden of disease, the clinical picture and the groups at higher risk of experiencing severe disease. It should not be assumed that this will be the same as the previous seasonal influenza. ECDC has identified eight priority areas for surveillance and research where it advises work should be undertaken to clarify these uncertainties, particularly in support of the new EU Health Council Recommendation on Seasonal Influenza Immunisation.
This document represents guidance from ECDC and does not necessarily represent the opinions of those who contributed to the work or their employing institutions. Comments on this forward look are welcomed and should be sent to influenza@ecdc.europa.eu.
Rationale of this risk assessment
This work is needed for a number of planning purposes, notably to inform decisions on short- and long-term influenza vaccination strategies. It is urgently required because:
Source, date and type of request
ECDC internal decision informed by discussion at the ECDC Advisory Forum No. 20 (8 December 2009).
Objectives
Specific objectives of the work are:
The processes that this will inform (though not necessarily determine) are:
Consulted experts
Internal ECDC experts. ECDC Advisory Forum members or individuals nominated by them, World Health Organization, relevant experts and specialists from EU and other countries, notably from WHO and EU pandemic modelling groups (Annex 1).
Background
This work is similar to that which ECDC undertook with its Advisory Forum (AF) (or their nominated representatives), WHO and other contributors for revising pandemic planning assumptions to fit the parameters of the 2009 pandemic. The outcome of that work was published in November on the ECDC websitei. There are also links with ECDC?s 2009 Pandemic Risk Assessments(ii)
The members of the group advising ECDC are listed in Annex I. There is continuity with the group which undertook the work on planning assumptions. However, ECDC again invited all AF members to join in the process or to nominate representatives and work undertaken by an ECDC Pandemic Modelling Group and a global group convened by WHO [2].(iii)
Terminology and assumptions
ECDC would like to thank all those who contributed to this work at what was an exceptionally busy period. A number of European countries have also been generous in sharing unpublished analyses and data and one of these appears as Annex II.
For this pandemic, ECDC finds it preferable to use the terms spring-summer wave and autumn-winter wave rather than first wave, second wave, etc. This is because the latter can be taken to imply that all countries will experience two or more pandemic waves which may not be the case
Previous experience is that all pandemics ?settle down? and dominate the new pattern of inter-pandemic influenza (also known as seasonal influenza), which can be significantly different in its characteristics from what was experienced prior to the pandemic (Table 1, Figure 1). The timeframe for the transition from a pandemic to a seasonal pattern is uncertain. As explained below, it can happen quite quickly (1957 pandemic) or take two seasons (1918 and 1968 pandemics) [3]. The formal name of the transition phase (which is still in the pandemic period) is ?post-peak? and it is followed by a post-pandemic phase, sometimes interrupted by a renewed wave (Table 2) [4].
Methodology, available information and evidence assessment
The methodology used was simple, to consider all relevant sources of data and analyses. Four data sources or types of analyses are available:
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(i) (LINK)
(ii) (LINK)
(iii) The names of those in the earlier group are at the bottom of the front page of the planning document. In addition, other members of the Advisory Forum, though unable to participate, expressed interest in the outcome and/or contributed to national data or analyses.
(iv) Information in [square brackets] means the countries or larger grouping from which data were made available either in published form or in confidence. In addition, there is important information on the apparent risk group and mortality data which differ somewhat from that seen for the previous seasonal influenza [9,10,11,12]. Further, to determine the risk and target groups for immunisation, data will be needed from the experience with the 2009 pandemic A(H1N1), especially concerning the risk factors associated with experiencing severe disease and death from this infection.
(i) Council Recommendation of 22 December 2009 on seasonal influenza vaccination (2009/1019/EU). Official Journal of the European Union. OJ L 348, 29 December 2009. (LINK)
(ii) Note the components of the vaccine are determined during meetings convened by WHO and EMA but information and analyses such as those contained here contribute to that process. WHO published their latest recommendation on 18 February: Recommended viruses for influenza vaccines for use in the 2010-2011 northern hemisphere influenza season. See also ECDC Public Health Development (19 February 2010).
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[Source Full PDF Document, European Centre for Diseases Prevention andControl (ECDC), March 8, 2010: LINK. EDITED.]
ECDC FORWARD LOOK RISK ASSESSMENT - Likely scenarios for influenza in 2010 and the 2010/2011 influenza season in Europe and the consequent work priorities
(...)
Executive summary
Work has been undertaken by ECDC with substantial input from its Advisory Forum, other European experts and WHO in order to inform EU stakeholders as to the likely scenarios for influenza transmission (pandemic and inter-pandemic) in Europe in the immediate future.
Specifically, this work has been looking at what can most reasonably be expected in the first half of 2010 and to the end of the 2010/11 influenza season. It has also identified the further information that needs to be gathered through surveillance and research in order to determine vaccine strategies, including implementation of the new EU Health Council Recommendation on seasonal influenza immunisation.
Evidence, data and information were considered from a number of sources including prior pandemics, the European experience during this pandemic, sero-epidemiology, modelling and especially what happened in the Southern Hemisphere in 2009/10 following their initial autumn/winter wave.
On the basis of this it seems unlikely that there will be another spring/summer pandemic wave in Europe unless there are significant unrecognised uninfected populations or the virus changes and becomes more transmissible.
Serological surveys (measuring the levels of immunity in the community) could help reduce this uncertainty.
However, only a limited number of Member States are currently using this tool to assess susceptibility. Other important data and analyses are lacking and hence priority work has been identified for Member States and ECDC to undertake, especially to inform vaccination strategies using the currently authorised monovalent pandemic vaccines and the anticipated 2010/2011 seasonal trivalent influenza vaccines (which will include the pandemic H1N1 strain).
It seems highly likely that even when WHO judges the post-peak and post-pandemic phases to have been reached, Europe will continue to experience low-level transmission and small outbreaks of the pandemic 2009 A(H1N1) influenza. This is the most likely scenario throughout the whole of 2010. However, larger outbreaks cannot be excluded given the lack of information from seroepidemiology.
Epidemic transmission of the pandemic virus is highly likely in the next (2010/2011) winter season, at least in very young children and other susceptible individuals. It is also most likely that pandemic influenza A(H1N1) will become the dominant virus in the coming winter season along with influenza B viruses, though the presence of influenza A(H3N2) viruses as well cannot presently be excluded. By then Europe will probably be referring to this combination as the ?new seasonal influenza?.
There is currently no evidence of a changed pathogenicity of the circulating pandemic influenza virus.
No significant genetic or antigenic changes to the pandemic influenza virus have so far been reported and so patterns in morbidity and mortality similar to those seen during the pandemic should initially be expected from this virus next winter though numbers of cases will be considerably smaller because of the previous transmission and vaccination.
In summary, the implications for vaccination strategies from this conservative forward look is that transmission of the pandemic virus will continue through 2010 albeit at low levels, and that this will be the predominant influenza A virus causing seasonal influenza in the winter of 2010/2011. At present the currently authorised monovalent pandemic vaccines and the new 2010/2011 seasonal influenza vaccines are likely to be effective against the 2009 A(H1N1) strain for the coming 6?10 months. Therefore, for Member States wishing to protect unimmunised citizens in the spring of 2010 and autumn/winter of 2010?2011, there will be advantages to continuing to offer these vaccines (or trivalent vaccines with the pandemic antigen when they are available) to their chosen risk and target groups. ECDC?s advice to EU citizens remains to accept influenza vaccination when it is offered to them.
Influenza viruses are notorious for their unpredictability and so this forward look risk assessment must not be seen as representing anything more than the most likely scenario. It will also be updated as relevant and significant data become available.
There are a number of uncertainties about the new seasonal influenza that Europe will face in the winter of 2010/11 concerning the burden of disease, the clinical picture and the groups at higher risk of experiencing severe disease. It should not be assumed that this will be the same as the previous seasonal influenza. ECDC has identified eight priority areas for surveillance and research where it advises work should be undertaken to clarify these uncertainties, particularly in support of the new EU Health Council Recommendation on Seasonal Influenza Immunisation.
This document represents guidance from ECDC and does not necessarily represent the opinions of those who contributed to the work or their employing institutions. Comments on this forward look are welcomed and should be sent to influenza@ecdc.europa.eu.
Rationale of this risk assessment
This work is needed for a number of planning purposes, notably to inform decisions on short- and long-term influenza vaccination strategies. It is urgently required because:
- authorities need to decide whether to continue pandemic vaccination in 2010;
- it cannot be assumed that the pandemic is over;
- previous recommendations about risk and target groups in the EU should be revisited, preferably before the summer, as the ones for the previous seasonal influenza may no longer entirely apply [1].
Source, date and type of request
ECDC internal decision informed by discussion at the ECDC Advisory Forum No. 20 (8 December 2009).
Objectives
Specific objectives of the work are:
- to inform Member States, the European Commission, the European Medicines Agency and others as to possible scenarios for influenza transmission (pandemic and inter-pandemic) that can reasonably be expected, or excluded, in the first half of 2010 in Europe and more tentatively through to the end of the 2010/2011 influenza season; and
- to determine what further information is needed to inform vaccine strategies including implementation of the new EU Health Council Recommendation on seasonal influenza immunisation(i)
The processes that this will inform (though not necessarily determine) are:
- Planning for possible pressures on health services in early 2010.
- Decisions on continuation of vaccination with the specific pandemic vaccines.
- Selection of the vaccine components and formulation for the 2010/2011 season(ii)
- Elaboration of more detailed seasonal vaccine strategies, including identification of the risk groups and other groups to be offered seasonal vaccination. .
Consulted experts
Internal ECDC experts. ECDC Advisory Forum members or individuals nominated by them, World Health Organization, relevant experts and specialists from EU and other countries, notably from WHO and EU pandemic modelling groups (Annex 1).
Background
This work is similar to that which ECDC undertook with its Advisory Forum (AF) (or their nominated representatives), WHO and other contributors for revising pandemic planning assumptions to fit the parameters of the 2009 pandemic. The outcome of that work was published in November on the ECDC websitei. There are also links with ECDC?s 2009 Pandemic Risk Assessments(ii)
The members of the group advising ECDC are listed in Annex I. There is continuity with the group which undertook the work on planning assumptions. However, ECDC again invited all AF members to join in the process or to nominate representatives and work undertaken by an ECDC Pandemic Modelling Group and a global group convened by WHO [2].(iii)
Terminology and assumptions
ECDC would like to thank all those who contributed to this work at what was an exceptionally busy period. A number of European countries have also been generous in sharing unpublished analyses and data and one of these appears as Annex II.
For this pandemic, ECDC finds it preferable to use the terms spring-summer wave and autumn-winter wave rather than first wave, second wave, etc. This is because the latter can be taken to imply that all countries will experience two or more pandemic waves which may not be the case
Previous experience is that all pandemics ?settle down? and dominate the new pattern of inter-pandemic influenza (also known as seasonal influenza), which can be significantly different in its characteristics from what was experienced prior to the pandemic (Table 1, Figure 1). The timeframe for the transition from a pandemic to a seasonal pattern is uncertain. As explained below, it can happen quite quickly (1957 pandemic) or take two seasons (1918 and 1968 pandemics) [3]. The formal name of the transition phase (which is still in the pandemic period) is ?post-peak? and it is followed by a post-pandemic phase, sometimes interrupted by a renewed wave (Table 2) [4].
Methodology, available information and evidence assessment
The methodology used was simple, to consider all relevant sources of data and analyses. Four data sources or types of analyses are available:
- Observations of what happened in the Southern Hemisphere temperate countries in their 2009/2010 spring and summer [Australia, Chile, New Zealand and South Africa](iv)
- Observations of what happened during previous pandemics and inter-pandemic periods (Figure 1), with particular attention being paid to the 1957 and 1968 pandemics [Italy, Spain, Sweden, UK and USA]. . What is happening in other regions of the world [5] and in Europe in the winter of 2009/2010 [6,7].
- Estimations of the likely numbers and proportions of people who are immune due to prior immunity, by having been infected during this pandemic or from being immunised [France, Germany, UK]. Hence, from these estimations, whether there are sufficient susceptible individuals to sustain transmission. Because of the difficulties of dealing with overlapping estimations and the indeterminate sizes of the overlap, particular attention should be paid to the serological data becoming available.
- Mathematical modelling based on the above assessments. Especially, estimations of the proportions of the population that are needed to be immune for transmission to terminate given the transmission characteristics (especially the values for R) observed to date [EU Modeling Group, Germany, UK] [2,8].
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(i) (LINK)
(ii) (LINK)
(iii) The names of those in the earlier group are at the bottom of the front page of the planning document. In addition, other members of the Advisory Forum, though unable to participate, expressed interest in the outcome and/or contributed to national data or analyses.
(iv) Information in [square brackets] means the countries or larger grouping from which data were made available either in published form or in confidence. In addition, there is important information on the apparent risk group and mortality data which differ somewhat from that seen for the previous seasonal influenza [9,10,11,12]. Further, to determine the risk and target groups for immunisation, data will be needed from the experience with the 2009 pandemic A(H1N1), especially concerning the risk factors associated with experiencing severe disease and death from this infection.
(i) Council Recommendation of 22 December 2009 on seasonal influenza vaccination (2009/1019/EU). Official Journal of the European Union. OJ L 348, 29 December 2009. (LINK)
(ii) Note the components of the vaccine are determined during meetings convened by WHO and EMA but information and analyses such as those contained here contribute to that process. WHO published their latest recommendation on 18 February: Recommended viruses for influenza vaccines for use in the 2010-2011 northern hemisphere influenza season. See also ECDC Public Health Development (19 February 2010).
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