The authors did a very good job of collaborating across the globe to get a large data set of single year age data. I do wonder however, why they didn’t include a more robust literature review of the pre-2009 serum cultures other countries have been doing that prove largely the same conclusions found in this paper. (1) Those studies were considerably smaller but in my mind provided the basis of these authors work. Another limitation to this study was the inability to control for the differences in hospitalization rates among different sub-sets of the population being studied. The authors admit that certain regions have different criteria for admission to the hospital or different levels of access to hospitals. However, there are many other reasons why splitting the data based on hospitalization status may not be the most indicative of true levels of disease severity in the population. For cultural reasons certain genders or ethnicities may be disproportionately underrepresented in hospitals, also age, socioeconomic status, other comorbidities, even job status could prevent your ability to rely on a hospital for care. Finally, I also think the authors could have provided a greater discussion of future work that needs to be done in this field.
The policy implications of this study are interesting to explore. Seasonal flu jabs are important for the seasonal flu at hand but it can also be important later in life if a pandemic flu develops that is antigenically similar to the immunity you received from your flu inoculation when you were younger. The idea that a public health intervention that occurs at a relatively young age may protect you when you are old and frail should have an impact on our thinking on who should get a seasonal flu vaccination. This is also important to consider economically when weighing the costs and benefits of a flu vaccination program. These inoculations may have both short and long term benefits.
1. Ikonen N, Strengell M, Kinnunen L, Österlund P, Pirhonen J, Broman M, Davidkin I, Ziegler T, Julkunen I. High frequency of crossreacting antibodies against 2009 pandemic influenza A(H1N1) virus among the elderly in Finland. Euro Surveill. 2010;15(5). Available online: http://www.eurosurveillan...
Miller E, Hoschler K, Hardelid P, Stanford E, Andrews N, Zambon M. Incidence of 2009 pandemic influenza A H1N1 infection in England: a cross-sectional serological study. Lancet. Published Online 21 January 2010.
Prachayangprecha S, Makkoch J, Payungporn S, Chieochansin T, Vuthitanachot C, et al. (2010) Serological analysis of human pandemic influenza (H1N1)in Thailand. J Health