Influenza
Conditions
Keywords
Influenza, Influenza type A, Influenza type B, hospitalization, Manitoba, Canada
Brief summary
This study compares the epidemiology and clinical outcomes of laboratory confirmed influenza type A to type B following clinical diagnosis of influenza. Multivariate models are used to assess the effects of influenza type on clinical outcomes while accounting for potential confounders.
Detailed description
Annual epidemics of influenza are an important public health problem globally and in Canada. Each year, 10-25% of the Canadian population become infected with influenza. Most of these infections are typically asymptomatic or associated with a mild self-limiting illness. However, influenza can cause severe illness leading to hospitalization and death, especially among the very young, the elderly and among those with underlying chronic conditions. It has been estimated that on average about 4,000 influenza-related deaths occur in Canada each year. In addition, the economic burden of influenza is significant because of the high direct costs associated with increased utilization of services and the indirect costs caused by school and work absenteeism. This project compares laboratory-confirmed cases of influenza A and B in terms of their epidemiology, and the overall and cause-specific incidence rates of important clinical outcomes including physician visits, hospitalization and death following clinical diagnosis of influenza cases in Manitoba over the period from 1993 to 2008. The study assesses secular and seasonal trends in the incidence rates of influenza A and B cases in Manitoba during the period of 1993-2008, to determine whether these rates vary for different subsets of the population defined by demographic (e.g., age group, gender), socioeconomic, geographic (neighborhood of residence) and clinical (e.g., vaccination, presence of chronic conditions, immune status) characteristics. The analysis by influenza type then compares the overall and cause-specific incidence rates of physician visits, hospitalization and death following the diagnosis of a laboratory-confirmed influenza. The effects of influenza type on clinical outcomes (e.g., hospitalization) are assessed with multivariate models while accounting for potential confounding by demographic, socioeconomic, geographic and clinical (e.g., co-morbidity, immune status) characteristics.
Interventions
None listed
Sponsors
International Centre for Infectious Diseases, Canada
Study design
Observational model
COHORT
Time perspective
RETROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
6 Months to No maximum
Healthy volunteers
No
Inclusion criteria
* Any person who normally resides in Manitoba and who has been continuously covered by Manitoba Health during the study period will be eligible for inclusion in the study.
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Risk of Death Due to Any Cause During 30 Days Following the Index Date of Laboratory Confirmed Cases of Influenza A and B in the Province of Manitoba | Upto 15 years |
| Age Adjusted Percentage of Participants With a Physician Visit Due to Any Diagnosis Within 30 Days of the Index Date of the Confirmed Influenza A and B Cases in the Province of Manitoba | up to 15 years |
| Percentage of Participants With a Risk of Hospitalization Due to Any Diagnosis Within 30 Days Following the Index Date of Confirmed Cases of Influenza A and B in the Province of Manitoba | upto 15 years |
Countries
Canada
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Confirmed Cases of Influenza A Laboratory confirmed cases of influenza A diagnosed by PCR, viral culture or florescence microscopy | 1,404 |
| Confirmed Cases of Influenza B Laboratory confirmed cases of influenza B diagnosed by PCR, viral culture or florescence microscopy | 445 |
| Total | 1,849 |
Baseline characteristics
| Characteristic | Confirmed Cases of Influenza A | Confirmed Cases of Influenza B | Total |
|---|---|---|---|
| Age, Categorical <=18 years | 511 Participants | 236 Participants | 747 Participants |
| Age, Categorical >=65 years | 568 Participants | 80 Participants | 648 Participants |
| Age, Categorical Between 18 and 65 years | 325 Participants | 129 Participants | 454 Participants |
| Region of Enrollment Canada | 1404 participants | 445 participants | 1849 participants |
| Sex: Female, Male Female | 758 Participants | 245 Participants | 1003 Participants |
| Sex: Female, Male Male | 646 Participants | 200 Participants | 846 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 0 / 0 | 0 / 0 |
| serious Total, serious adverse events | 0 / 0 | 0 / 0 |
Outcome results
Primary
Age Adjusted Percentage of Participants With a Physician Visit Due to Any Diagnosis Within 30 Days of the Index Date of the Confirmed Influenza A and B Cases in the Province of Manitoba
Time frame: up to 15 years
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Confirmed Cases of Influenza A | Age Adjusted Percentage of Participants With a Physician Visit Due to Any Diagnosis Within 30 Days of the Index Date of the Confirmed Influenza A and B Cases in the Province of Manitoba | 23.5 Percentage of participants |
| Confirmed Cases of Influenza B | Age Adjusted Percentage of Participants With a Physician Visit Due to Any Diagnosis Within 30 Days of the Index Date of the Confirmed Influenza A and B Cases in the Province of Manitoba | 22.1 Percentage of participants |
Primary
Percentage of Participants With a Risk of Hospitalization Due to Any Diagnosis Within 30 Days Following the Index Date of Confirmed Cases of Influenza A and B in the Province of Manitoba
Time frame: upto 15 years
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Confirmed Cases of Influenza A | Percentage of Participants With a Risk of Hospitalization Due to Any Diagnosis Within 30 Days Following the Index Date of Confirmed Cases of Influenza A and B in the Province of Manitoba | 9.0 Percentage of participants |
| Confirmed Cases of Influenza B | Percentage of Participants With a Risk of Hospitalization Due to Any Diagnosis Within 30 Days Following the Index Date of Confirmed Cases of Influenza A and B in the Province of Manitoba | 7.0 Percentage of participants |
Primary
Risk of Death Due to Any Cause During 30 Days Following the Index Date of Laboratory Confirmed Cases of Influenza A and B in the Province of Manitoba
Time frame: Upto 15 years
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Confirmed Cases of Influenza A | Risk of Death Due to Any Cause During 30 Days Following the Index Date of Laboratory Confirmed Cases of Influenza A and B in the Province of Manitoba | 4.5 percentage of participants |
| Confirmed Cases of Influenza B | Risk of Death Due to Any Cause During 30 Days Following the Index Date of Laboratory Confirmed Cases of Influenza A and B in the Province of Manitoba | 2.0 percentage of participants |