tetano
Editor, Senior Moderator
Camille Pelat1,2*, Alessandra Falchi1,2, Fabrice Carrat1,2,3, Anne Mosnier4, Isabelle Bonmarin5, Cl?ment Turbelin1,2, Sophie Vaux5, Sylvie van der Werf6,7,8, Jean Marie Cohen4, Bruno Lina9, Thierry Blanchon1,2, Thomas Hanslik2,10,11
1 UPMC Universit? Paris 06, UMRS 707, Paris, France, 2 U707, INSERM, Paris, France, 3 Unit? de Sant? Publique, H?pital Saint-Antoine, Assistance Publique-H?pitaux de Paris, Paris, France, 4 R?seau des GROG, Groupes R?gionaux d'Observation de la Grippe, Paris, France, 5 Institut de Veille Sanitaire, Saint-Maurice, France, 6 Unit of Molecular Genetics of RNA Viruses, National Influenza Center (Northern-France), Department of Virology, Institut Pasteur, Paris, France, 7 URA3015, CNRS, Paris, France, 8 Universit? Paris Diderot, Sorbonne Paris Cit?, Paris, France, 9 Laboratoire de Virologie, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, CNR des Virus Influenzae - R?gion Sud, Bron, France, 10 Service de M?decine Interne, H?pital Ambroise-Par?, Assistance Publique-H?pitaux de Paris, Boulogne Billancourt, France, 11 Universit? Versailles-Saint-Quentin-en-Yvelines, Versailles, France
Abstract Top
Background
In this study, we assess how effective pandemic and trivalent 2009-2010 seasonal vaccines were in preventing influenza-like illness (ILI) during the 2009 A(H1N1) pandemic in France. We also compare vaccine effectiveness against ILI versus laboratory-confirmed pandemic A(H1N1) influenza, and assess the possible bias caused by using non-specific endpoints and observational data.
Methodology and Principal Findings
We estimated vaccine effectiveness by using the following formula: VE = (PPV-PCV)/(PPV(1-PCV)) ? 100%, where PPV is the proportion vaccinated in the population and PCV the proportion of vaccinated influenza cases. People were considered vaccinated three weeks after receiving a dose of vaccine. ILI and pandemic A(H1N1) laboratory-confirmed cases were obtained from two surveillance networks of general practitioners. During the epidemic, 99.7% of influenza isolates were pandemic A(H1N1). Pandemic and seasonal vaccine uptakes in the population were obtained from the National Health Insurance database and by telephonic surveys, respectively. Effectiveness estimates were adjusted by age and week. The presence of residual biases was explored by calculating vaccine effectiveness after the influenza period. The effectiveness of pandemic vaccines in preventing ILI was 52% (95% confidence interval: 30?69) during the pandemic and 33% (4?55) after. It was 86% (56?98) against confirmed influenza. The effectiveness of seasonal vaccines against ILI was 61% (56?66) during the pandemic and 19% (−10?41) after. It was 60% (41?74) against confirmed influenza.
Conclusions
The effectiveness of pandemic vaccines in preventing confirmed pandemic A(H1N1) influenza on the field was high, consistently with published findings. It was significantly lower against ILI. This is unsurprising since not all ILI cases are caused by influenza. Trivalent 2009-2010 seasonal vaccines had a statistically significant effectiveness in preventing ILI and confirmed pandemic influenza, but were not better in preventing confirmed pandemic influenza than in preventing ILI. This lack of difference might be indicative of selection bias.
Citation: Pelat C, Falchi A, Carrat F, Mosnier A, Bonmarin I, et al. (2011) Field Effectiveness of Pandemic and 2009-2010 Seasonal Vaccines against 2009-2010 A(H1N1) Influenza: Estimations from Surveillance Data in France. PLoS ONE 6(5): e19621. doi:10.1371/journal.pone.0019621
Editor: Benjamin J. Cowling, University of Hong Kong, Hong Kong
Received: November 11, 2010; Accepted: April 8, 2011; Published: May 10, 2011
Copyright: ? 2011 Pelat et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was funded by a European Vaccine Manufacturers grant through the Epiconcept society. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019621
1 UPMC Universit? Paris 06, UMRS 707, Paris, France, 2 U707, INSERM, Paris, France, 3 Unit? de Sant? Publique, H?pital Saint-Antoine, Assistance Publique-H?pitaux de Paris, Paris, France, 4 R?seau des GROG, Groupes R?gionaux d'Observation de la Grippe, Paris, France, 5 Institut de Veille Sanitaire, Saint-Maurice, France, 6 Unit of Molecular Genetics of RNA Viruses, National Influenza Center (Northern-France), Department of Virology, Institut Pasteur, Paris, France, 7 URA3015, CNRS, Paris, France, 8 Universit? Paris Diderot, Sorbonne Paris Cit?, Paris, France, 9 Laboratoire de Virologie, Centre de Biologie et de Pathologie Est, Hospices Civils de Lyon, CNR des Virus Influenzae - R?gion Sud, Bron, France, 10 Service de M?decine Interne, H?pital Ambroise-Par?, Assistance Publique-H?pitaux de Paris, Boulogne Billancourt, France, 11 Universit? Versailles-Saint-Quentin-en-Yvelines, Versailles, France
Abstract Top
Background
In this study, we assess how effective pandemic and trivalent 2009-2010 seasonal vaccines were in preventing influenza-like illness (ILI) during the 2009 A(H1N1) pandemic in France. We also compare vaccine effectiveness against ILI versus laboratory-confirmed pandemic A(H1N1) influenza, and assess the possible bias caused by using non-specific endpoints and observational data.
Methodology and Principal Findings
We estimated vaccine effectiveness by using the following formula: VE = (PPV-PCV)/(PPV(1-PCV)) ? 100%, where PPV is the proportion vaccinated in the population and PCV the proportion of vaccinated influenza cases. People were considered vaccinated three weeks after receiving a dose of vaccine. ILI and pandemic A(H1N1) laboratory-confirmed cases were obtained from two surveillance networks of general practitioners. During the epidemic, 99.7% of influenza isolates were pandemic A(H1N1). Pandemic and seasonal vaccine uptakes in the population were obtained from the National Health Insurance database and by telephonic surveys, respectively. Effectiveness estimates were adjusted by age and week. The presence of residual biases was explored by calculating vaccine effectiveness after the influenza period. The effectiveness of pandemic vaccines in preventing ILI was 52% (95% confidence interval: 30?69) during the pandemic and 33% (4?55) after. It was 86% (56?98) against confirmed influenza. The effectiveness of seasonal vaccines against ILI was 61% (56?66) during the pandemic and 19% (−10?41) after. It was 60% (41?74) against confirmed influenza.
Conclusions
The effectiveness of pandemic vaccines in preventing confirmed pandemic A(H1N1) influenza on the field was high, consistently with published findings. It was significantly lower against ILI. This is unsurprising since not all ILI cases are caused by influenza. Trivalent 2009-2010 seasonal vaccines had a statistically significant effectiveness in preventing ILI and confirmed pandemic influenza, but were not better in preventing confirmed pandemic influenza than in preventing ILI. This lack of difference might be indicative of selection bias.
Citation: Pelat C, Falchi A, Carrat F, Mosnier A, Bonmarin I, et al. (2011) Field Effectiveness of Pandemic and 2009-2010 Seasonal Vaccines against 2009-2010 A(H1N1) Influenza: Estimations from Surveillance Data in France. PLoS ONE 6(5): e19621. doi:10.1371/journal.pone.0019621
Editor: Benjamin J. Cowling, University of Hong Kong, Hong Kong
Received: November 11, 2010; Accepted: April 8, 2011; Published: May 10, 2011
Copyright: ? 2011 Pelat et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was funded by a European Vaccine Manufacturers grant through the Epiconcept society. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019621