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Usefulness of health registries when estimating vaccine effectiveness during the influenza A(H1N1)pdm09 pandemic in Norway.

Guzmán Herrador BR, Aavitsland P, Feiring B, Riise Bergsaker MA, Borgen K - BMC Infect. Dis. (2012)

Bottom Line: Based on these registries, we aimed at estimating the vaccine effectiveness (VE) and describing vaccine failures during the pandemic in Norway, in order to evaluate the role of the vaccine as a preventive measure during the pandemic.More than 30% of the vaccine failures were found in people below 10 years of age.It is also important to consider including information on underlying diseases in registries already existing, in order to make it feasible to conduct more complete VE estimations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway. BernardoRafael.Guzman.Herrador@fhi.no

ABSTRACT

Background: During the 2009-2010 pandemic in Norway, 12 513 laboratory-confirmed cases of pandemic influenza A(H1N1)pdm09, were reported to the Norwegian Surveillance System for Communicable Diseases (MSIS). 2.2 million persons (45% of the population) were vaccinated with an AS03-adjuvanted monovalent vaccine during the pandemic. Most of them were registered in the Norwegian Immunisation Registry (SYSVAK). Based on these registries, we aimed at estimating the vaccine effectiveness (VE) and describing vaccine failures during the pandemic in Norway, in order to evaluate the role of the vaccine as a preventive measure during the pandemic.

Methods: We conducted a population-based retrospective cohort study, linking MSIS and SYSVAK with pandemic influenza vaccination as exposure and laboratory-confirmed pandemic influenza as outcome. We measured VE by week and defined two thresholds for immunity; eight and 15 days after vaccination.

Results: The weekly VE ranged from 77% to 96% when considering 15 days or more after vaccination as the threshold of immunity and from 73% to 94% when considering eight days or more. Overall, 157 individuals contracted pandemic influenza eight or more days after vaccination (8.4/100,000 vaccinated), of these 58 had onset 15 days or more after vaccination (3.0/100,000 vaccinated). Most of the vaccine failures occurred during the first weeks of the vaccination campaign. More than 30% of the vaccine failures were found in people below 10 years of age.

Conclusions: Having available health registries with data regarding cases of specific disease and vaccination makes it feasible to estimate VE in a simple and rapid way. VE was high regardless the immunity threshold chosen. We encourage public health authorities in other countries to set up such registries. It is also important to consider including information on underlying diseases in registries already existing, in order to make it feasible to conduct more complete VE estimations.

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Related in: MedlinePlus

Rates of vaccine failures per week and overall during the main wave of the influenza pandemic in Norway. Rates of vaccine failures (per 100,000 vaccinated) per week and overall of the AS03-adjuvanted monovalent vaccine during the main wave (weeks 45-53, 2009) of the influenza pandemic in Norway. Blue bars indicate immunity as eight days and later after vaccination; red bars as 15 days and later.
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Figure 1: Rates of vaccine failures per week and overall during the main wave of the influenza pandemic in Norway. Rates of vaccine failures (per 100,000 vaccinated) per week and overall of the AS03-adjuvanted monovalent vaccine during the main wave (weeks 45-53, 2009) of the influenza pandemic in Norway. Blue bars indicate immunity as eight days and later after vaccination; red bars as 15 days and later.

Mentions: A total of 157 individuals were considered vaccine failures, i.e. they had onset of symptoms of pandemic influenza eight days or more after vaccination (8.4 per 100,000 vaccinated). When defining vaccine failure as those who had onset 15 days or more after vaccination, the number of vaccine failures decreased to 58 (3.0 per 100,000 vaccinated). There were slightly more females than males: 33 (52%) when using 15 days or more as the immunity threshold and 81 (57%) when using eight days. Most of the vaccine failures occurred during the first weeks of the vaccination campaign. After week 46, the proportion of failures decreased gradually to become minimal during the last weeks of the year (Figure 1).


Usefulness of health registries when estimating vaccine effectiveness during the influenza A(H1N1)pdm09 pandemic in Norway.

Guzmán Herrador BR, Aavitsland P, Feiring B, Riise Bergsaker MA, Borgen K - BMC Infect. Dis. (2012)

Rates of vaccine failures per week and overall during the main wave of the influenza pandemic in Norway. Rates of vaccine failures (per 100,000 vaccinated) per week and overall of the AS03-adjuvanted monovalent vaccine during the main wave (weeks 45-53, 2009) of the influenza pandemic in Norway. Blue bars indicate immunity as eight days and later after vaccination; red bars as 15 days and later.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3344681&req=5

Figure 1: Rates of vaccine failures per week and overall during the main wave of the influenza pandemic in Norway. Rates of vaccine failures (per 100,000 vaccinated) per week and overall of the AS03-adjuvanted monovalent vaccine during the main wave (weeks 45-53, 2009) of the influenza pandemic in Norway. Blue bars indicate immunity as eight days and later after vaccination; red bars as 15 days and later.
Mentions: A total of 157 individuals were considered vaccine failures, i.e. they had onset of symptoms of pandemic influenza eight days or more after vaccination (8.4 per 100,000 vaccinated). When defining vaccine failure as those who had onset 15 days or more after vaccination, the number of vaccine failures decreased to 58 (3.0 per 100,000 vaccinated). There were slightly more females than males: 33 (52%) when using 15 days or more as the immunity threshold and 81 (57%) when using eight days. Most of the vaccine failures occurred during the first weeks of the vaccination campaign. After week 46, the proportion of failures decreased gradually to become minimal during the last weeks of the year (Figure 1).

Bottom Line: Based on these registries, we aimed at estimating the vaccine effectiveness (VE) and describing vaccine failures during the pandemic in Norway, in order to evaluate the role of the vaccine as a preventive measure during the pandemic.More than 30% of the vaccine failures were found in people below 10 years of age.It is also important to consider including information on underlying diseases in registries already existing, in order to make it feasible to conduct more complete VE estimations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway. BernardoRafael.Guzman.Herrador@fhi.no

ABSTRACT

Background: During the 2009-2010 pandemic in Norway, 12 513 laboratory-confirmed cases of pandemic influenza A(H1N1)pdm09, were reported to the Norwegian Surveillance System for Communicable Diseases (MSIS). 2.2 million persons (45% of the population) were vaccinated with an AS03-adjuvanted monovalent vaccine during the pandemic. Most of them were registered in the Norwegian Immunisation Registry (SYSVAK). Based on these registries, we aimed at estimating the vaccine effectiveness (VE) and describing vaccine failures during the pandemic in Norway, in order to evaluate the role of the vaccine as a preventive measure during the pandemic.

Methods: We conducted a population-based retrospective cohort study, linking MSIS and SYSVAK with pandemic influenza vaccination as exposure and laboratory-confirmed pandemic influenza as outcome. We measured VE by week and defined two thresholds for immunity; eight and 15 days after vaccination.

Results: The weekly VE ranged from 77% to 96% when considering 15 days or more after vaccination as the threshold of immunity and from 73% to 94% when considering eight days or more. Overall, 157 individuals contracted pandemic influenza eight or more days after vaccination (8.4/100,000 vaccinated), of these 58 had onset 15 days or more after vaccination (3.0/100,000 vaccinated). Most of the vaccine failures occurred during the first weeks of the vaccination campaign. More than 30% of the vaccine failures were found in people below 10 years of age.

Conclusions: Having available health registries with data regarding cases of specific disease and vaccination makes it feasible to estimate VE in a simple and rapid way. VE was high regardless the immunity threshold chosen. We encourage public health authorities in other countries to set up such registries. It is also important to consider including information on underlying diseases in registries already existing, in order to make it feasible to conduct more complete VE estimations.

Show MeSH
Related in: MedlinePlus