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Field effectiveness of pandemic and 2009-2010 seasonal vaccines against 2009-2010 A(H1N1) influenza: estimations from surveillance data in France.
PLoS One. 2011 May 10; 6(5):e19621.Plos

Abstract

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.

Authors+Show Affiliations

UPMC Université Paris 06, UMRS 707, Paris, France. pelat@u707.jussieu.frNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21573005

Citation

Pelat, Camille, et al. "Field Effectiveness of Pandemic and 2009-2010 Seasonal Vaccines Against 2009-2010 A(H1N1) Influenza: Estimations From Surveillance Data in France." PloS One, vol. 6, no. 5, 2011, pp. e19621.
Pelat C, Falchi A, Carrat F, et al. Field effectiveness of pandemic and 2009-2010 seasonal vaccines against 2009-2010 A(H1N1) influenza: estimations from surveillance data in France. PLoS ONE. 2011;6(5):e19621.
Pelat, C., Falchi, A., Carrat, F., Mosnier, A., Bonmarin, I., Turbelin, C., Vaux, S., van der Werf, S., Cohen, J. M., Lina, B., Blanchon, T., & Hanslik, T. (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. https://doi.org/10.1371/journal.pone.0019621
Pelat C, et al. Field Effectiveness of Pandemic and 2009-2010 Seasonal Vaccines Against 2009-2010 A(H1N1) Influenza: Estimations From Surveillance Data in France. PLoS ONE. 2011 May 10;6(5):e19621. PubMed PMID: 21573005.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Field effectiveness of pandemic and 2009-2010 seasonal vaccines against 2009-2010 A(H1N1) influenza: estimations from surveillance data in France. AU - Pelat,Camille, AU - Falchi,Alessandra, AU - Carrat,Fabrice, AU - Mosnier,Anne, AU - Bonmarin,Isabelle, AU - Turbelin,Clément, AU - Vaux,Sophie, AU - van der Werf,Sylvie, AU - Cohen,Jean Marie, AU - Lina,Bruno, AU - Blanchon,Thierry, AU - Hanslik,Thomas, Y1 - 2011/05/10/ PY - 2010/11/11/received PY - 2011/04/08/accepted PY - 2011/5/17/entrez PY - 2011/5/17/pubmed PY - 2011/8/31/medline SP - e19621 EP - e19621 JF - PloS one JO - PLoS ONE VL - 6 IS - 5 N2 - 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. SN - 1932-6203 UR - https://www.unboundmedicine.com/medline/citation/21573005/Field_effectiveness_of_pandemic_and_2009_2010_seasonal_vaccines_against_2009_2010_A_H1N1__influenza:_estimations_from_surveillance_data_in_France_ L2 - http://dx.plos.org/10.1371/journal.pone.0019621 DB - PRIME DP - Unbound Medicine ER -