Incidence of Influenza in Ontario Following the Universal Influenza Immunization Campaign

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Incidence of Influenza in Ontario Following the
Universal Influenza Immunization Campaign

• Dianne Groll PhD, University of Ottawa
• David J Thomson PhD, Queens University
• CPHA 2005

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Background

• The Canadian National Advisory Committee on
  Immunization (NACI) has recommended yearly
  influenza vaccination for persons at high-risk
  for influenza-related complications since 1989
• In 1993, the publicly funded influenza
  immunization program in Ontario was expanded to
  include the vaccination of healthcare workers.
• In 1999 this program was expanded further to
  include all workers in long-term care facilities
  and hospitals, and all members of the regulated
  health professions.

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High-Risk Individuals Are

• Everyone 65 years of age or older
• Anyone with a serious, long-term health problem,
  such as heart, kidney, or lung disease
  (including asthma)
• Anyone with diabetes or other metabolic disease,
  cancer, or blood disorder
• Anyone whose immune system is weakened
• Anyone aged six months to 18 years on long-term
  treatment with acetylsalicylic acid (ASA).
• Anyone who lives, works, or volunteers in a
  nursing home, chronic care institution, or
  retirement home
• Healthcare workers and essential service workers
  (i.e., ambulance staff, fire and police)
• Anyone who volunteers in a hospital or other
  health care facility
• Anyone who lives in the same household as people
  in any high risk group who are unable to get
  vaccinated

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Background

• In July 2000, the Ministry of Health and Long
  Term Care of Ontario announced a Universal
  Influenza Immunization Program for all residents
  of Ontario extending the current coverage to
  include low-risk adults and children.
• Vaccination under this program started in October
  2000.
• The two identified objectives of this program
  were to
• Decrease the impact of influenza on emergency
  department visits, and
• Decrease the number and severity of cases of
  influenza in Ontario

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Who was Targeted by the Universal Influenza
Immunization Campaign

• Healthy individuals between the ages of 2 65
  not identified in any high risk category.

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Background

• In August 2001, the Ontario Minister of Health
  stated that the Campaign had been a success in
  reducing influenza and called for a second year
  at 43 million plus 3 million in advertising.
• Cumulative cost of this program as of 2004 is
  more than 200 million

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Present Study

• The purpose of this study was to compare the
  annual incidence of influenza in Ontario before
  and after the implementation of the Universal
  Influenza Immunization Campaign.

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Influenza Data Collection

• This is a population-based, retrospective study
  of laboratory-confirmed influenza cases as
  reported to Health Canada from January 1 1990
  August 31 2005.
• Provincial and national influenza data for 2002
  2005 were obtained from Health Canadas Flu
  Watch website (http//www.phac-aspc.gc.ca/fluwatc
  h). Ontario influenza data for 1990 2002 were
  obtained directly from Health Canada.
• This study used only the laboratory-confirmed
  cases of influenza only.

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Analysis

• All monthly influenza counts were changed to rate
  per 100,000 population using annual Ontario
  population estimates from Statistics Canada
  (www.statcan.ca).
• The percent of influenza found in Ontario with
  respect to the rest of Canada was calculated for
  the years 1996 2005 (years for which Flu Watch
  data for the country as a whole was available).

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Time Series Analysis

• We used multitaper method of time-series analysis
  supplemented by the harmonic F-test for periodic
  components.
• Multitaper analysis is similar to the commonly
  used Autoregressive Integrated Moving Average
  (ARIMA) method of first identifying the period by
  finding a peak in the autocorrelation function
  and then averaging periods to increase the
  signal-to-noise ratio.
• However the ARIMA period averaging method retains
  all periodic information, including harmonic
  content that is not statistically significant.
• The multitaper relies on an F-statistic to
  determine the statistical significance of
  individual harmonics leaving out statistically
  insignificant harmonics, thereby reducing
  spurious noise in the signal

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Vaccination Coverage

• Information on the number of vaccines distributed
  and the proportion of high and low risk
  individuals vaccinated was obtained from
  published Health Canada Sources.
• Vaccination data was collected through telephone
  interviews and from the National Population
  Health Survey and the Canadian Community Health
  Survey

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Results
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Monthly Ontario Influenza Rates per 100,000
PopulationJanuary 1990 August 2005
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Time Series Analysis

• Multitaper analysis shows that there has been no
  significant decrease in mean monthly influenza
  cases between 1990/2000 and 2000/05.
• In addition to the annual component, there is a
  strong periodic component at 4 cycles/year
  (3.25 months), plt0.01, and a component at 4.8
  (5)-year cycle significant at the plt0.05 level.

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Why no Change?

• Lack of change in influenza rate may be a result
  of increased awareness and thus increased
  reporting.
• Look at influenza rates in other provinces
  compare rate ratios
• Look at the number of cases in Ontario with
  respect to the rest of Canada - of cases in
  Ontario.
• Look at coverage did it decrease?

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Annual Influenza Rates per 100,000 Population
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Number of influenza cases and of cases in
Ontario
Mean 1995 2000 31.9, Mean 2000 2005
32.0
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Influenza Vaccination RatesBy age, presence of
chronic conditions, household population aged 20
or older
Dr. Karim Kurji, Associate Chief Medical Officer
of Health National Influenza Vaccine Summit,
Atlanta, U.S.A., April 2004
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Vaccine Uptake/Vaccine Costs
Dr. Karim Kurji, Associate Chief Medical Officer
of Health National Influenza Vaccine Summit,
Atlanta, U.S.A., April 2004
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Limitations

• There is presently no systematic data collection
  regarding vaccination status of individuals and
  subsequent health outcomes.
• There was no systematically collected baseline
  data prior to the implementation of this program,
  so all evaluations will rely on the same data as
  used in this analysis.

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Conclusions

• There has not been a significant reduction in
  influenza cases in Ontario following the
  introduction of the Universal Influenza
  Immunization Campaign.