Incidence of Influenza in Ontario Following the Universal Influenza

Immunization Campaign

Dianne Groll PhD, University of Ottawa

David J Thomson PhD, Queen’s UniversityCPHA 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.

•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

High-Risk Individuals Are:

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

Monthly Ontario Influenza Rates per 100,000 PopulationJanuary 1990 – August 2005

0

20

40

60

80

100

120

140

160

180

Jan

-90

Jul-

90

Jan

-91

Jul-

91

Jan

-92

Jul-

92

Jan

-93

Jul-

93

Jan

-94

Jul-

94

Jan

-95

Jul-

95

Jan

-96

Jul-

96

Jan

-97

Jul-

97

Jan

-98

Jul-

98

Jan

-99

Jul-

99

Jan

-00

Jul-

00

Jan

-01

Jul-

01

Jan

-02

Jul-

02

Jan

-03

Jul-

03

Jan

-04

Jul-

04

Jan

-05

Jul-

05

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), p<0.01, and a component at ~4.8 (5)-year cycle significant at the p<0.05 level.

1999 - 2000 2000 - 2005

Multitaper average monthly number of cases 109.5 164

Standard Deviation 20 50.3

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

0

50

100

150

200

250

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

rate

per

100

,000

ONT QUE BC Prarie Maritime Canada

Year19951996

19961997

19971998

19981999

19992000

20002001

20012002

20022003

20032004

20042005

Ont. 222 537 1466 1329 2899 852 2249 936 4512 5135

Canada 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

Number of influenza cases and % of cases in Ontario

Mean 1995 – 2000 = 31.9%, Mean 2000 – 2005 = 32.0%

Influenza Vaccination RatesBy age, presence of chronic conditions, household population aged 20 or

older

Age 65 or older At leastone Chronic condition +

Total populationage 20 or older

1996/97 2000/01 1996/97 2000/01 1996/97 2000/01% % %

Ontario 59.5 72.5 39.1 58.2 18.4 37.0

Canada 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

FiscalYear

Vaccine Doses Provincial GovernmentCosts

Distributed Administered Coverage%

Vaccine($)

Total($)

1999/2000 2.10 million 1.90 million 16 3.97 m 7.41 m

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.