H1N1 (Swine Flu): The ECDC looks forward: Flu risk assessment with likely scenarios for 2010 and the 2010/2011 Influenza season in Europe
The ECDC (The European version of the CDC) has just published an interesting work trying to gauge the likely scenario for the flu in Europe for the next year. This is to help them with resource allocation and vaccine planning. The work was done in conjunction with their Advisory Forum, other European health experts and the WHO.
The work was specifically designed to “imagine” what could 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 additional information that needs to be gathered through surveillance and research in order to determine vaccine strategies.
Evidence, data and information were considered from a number of sources including prior pandemics, the European experience during this pandemic, sero-epidemiology, modeling and especially what happened in the Southern Hemisphere in 2009/10 following their initial autumn/winter wave.
The findings are presented in a short, well-documented paper:
- On the basis of this it seems unlikely that there will be another spring/summer pandemic wave in Europe unless there are significant unrecognized 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 authorized 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 authorized 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. 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 would be the same as the previous seasonal influenza.
Keep in mind, as the researchers note, that influenza is highly unpredictable…best words of advice – get vaccinated, pay attention and keep your plans current.