Transcript Incidence of Influenza in Ontario Following the Universal Influenza Immunization Campaign Dianne Groll PhD, University of Ottawa David J Thomson PhD, Queen’s University CPHA 2005

Incidence of Influenza in Ontario
Following the Universal Influenza
Immunization Campaign
Dianne Groll PhD, University of Ottawa
David J Thomson PhD, Queen’s University
CPHA 2005
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.
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
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
Who was Targeted by the
Universal Influenza Immunization
Campaign
• Healthy individuals between the ages of 2 – 65
not identified in any high risk category.
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
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.
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 Canada’s ‘Flu Watch’ website
(http://www.phac-aspc.gc.ca/fluwatch). Ontario influenza
data for 1990 – 2002 were obtained directly from Health
Canada.
• This study used only the laboratory-confirmed cases of
influenza only.
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).
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
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
Results
0
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
Jul-97
Jan-97
Jul-96
Jan-96
Jul-95
Jan-95
Jul-94
Jan-94
Jul-93
Jan-93
Jul-92
Jan-92
Jul-91
Jan-91
Jul-90
Jan-90
Monthly Ontario Influenza Rates per 100,000 Population
January 1990 – August 2005
180
160
140
120
100
80
60
40
20
Time Series Analysis
Multitaper average monthly number of cases
Standard Deviation
1999 - 2000
2000 - 2005
109.5
164
20
50.3
• 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), p<0.01, and a
component at ~4.8 (5)-year cycle significant at the p<0.05
level.
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?
Annual Influenza Rates per 100,000 Population
250
rate per 100,000
200
150
100
50
0
1996
1997
ONT
1998
1999
QUE
BC
2000
2001
Prarie
2002
2003
Maritime
2004
Canada
2005
Number of influenza cases and % of cases in Ontario
Year
1995
1996
1996
1997
1997
1998
1998
1999
1999
2000
2000
2001
2001
2002
2002
2003
2003
2004
2004
2005
Ont.
222
537
1466
1329
2899
852
2249
936
4512
5135
1075
1930
3802
4203
7027
4154
6766
3480
11370
4162
20.7
27.8
38.6
31.6
41.2
20.5
33.2
26.9
39.7
39.9
Canada
%
Mean 1995 – 2000 = 31.9%,
Mean 2000 – 2005 = 32.0%
Influenza Vaccination Rates
By age, presence of chronic conditions, household population aged 20 or
older
Age 65 or older
1996/97
2000/01
At least
one Chronic condition +
1996/97
%
Ontario
Canada
2000/01
Total population
age 20 or older
1996/97
%
2000/01
%
59.5
72.5
39.1
58.2
18.4
37.0
51.1
66.8
33.8
47.2
15.5
28.1
Data sources: 1996/97 National Population Health Survey; 2000/01 Canadian Community Health Survey
+
Asthma, chronic bronchitis/emphysema, diabetes, heart disease, cancer, effects of stroke
Source: Statistics Canada : Health Reports, Vol 15, No 2. March 2004
Dr. Karim Kurji, Associate Chief Medical Officer of Health National Influenza
Vaccine Summit, Atlanta, U.S.A., April 2004
Vaccine Uptake/Vaccine Costs
Fiscal
Year
Vaccine Doses
Provincial Government
Costs
Vaccine
Total
($)
($)
3.97 m
7.41 m
Distributed
Administered
1999/2000
2.10 million
1.90 million
Coverage
%
16
2000/2001
7.90 million
5.76 million
44
17.3 m
40.2 m
2001/2002
6.00 million
4.90 million
42
18.5 m
~ 40 m
2002/2003
5.40 million
4.26 million
42
18.5 m
~ 40 m
2003/2004
6.01 million
5.52 million *
44 *
22.5 m
~ 42 m
* 2003/04 data is still being analyzed
Dr. Karim Kurji, Associate Chief Medical Officer of Health National Influenza Vaccine
Summit, Atlanta, U.S.A., April 2004
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.
Conclusions
There has not been a significant reduction in
influenza cases in Ontario following the
introduction of the Universal Influenza
Immunization Campaign.