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Influenza risk factors and ethnic differences Michael Baker Department of Public Health University of Otago, Wellington Outline • Risk factors for what? • Infection vs. Progression • Why identify risk factors? • Socio-demographic vs. Modifiable? • Hospitalisations in Auckland • Seasonal, 2000-09 • Pandemic influenza, 2009 • Conclusions & discussion points Infection vs. Progression Influenza susceptibility: Influenza progression cofactors: Influenza vaccination Chronic illness, Pregnancy Immune deficits School & Work exposure Age Obesity Obesity, Smoking Urban domicile Immune competence Pneumococcal immunisation Smoking Antiviral treatment Influenza exposure: Seasonal virus load Household crowding Children in house Weather Indoor air Influenza infection Age, Sex, Ethnicity Primary care access Quality of hospital care Influenza illness Serious influenza Influenza death Modifiable risk factors Risk factors for infection and/or poor outcome Evidence Exposure factors Household crowding * Poor indoor air quality in household * Susceptibility factors Lack of influenza vaccination *** Active & Passive smoke exposure ** Immune deficiencies ** Progression factors Micronutrient deficiencies eg vitamin D deficiency * Obesity * Chronic illness, eg COPD, asthma, diabetes ** Poor access to primary healthcare * Lack of antiviral treatments ** Lack of pneumococcal vaccination * Broad determinants Poverty ** Risk factors Influenza hospitalisations by year, Auckland 2000-10 (J09=474, J10=367, J11=569) 600 J09 Pandemic Influenza 500 J11 Clinical influenza Number 400 J10 Confirmed Influenza 300 200 100 0 2000 2001 2002 2003 2004 2005 Year 2006 2007 2008 2009 2010 Risk factors Numbers of Hospitalisations (2000-2008) Influenza hospitalisations by month, Auckland 2000-08 (Ref = Summer) 180 160 J11 Clinical influenza 140 J10 Confirmed Influenza 120 100 Winter RR=12.5 80 60 Winter RR=59.0 40 20 0 Jan Feb Mar Apr May Jun Months Jul Aug Sep Oct Nov Dec Risk factors Influenza hospitalisation rate by age group, Auckland 2000-08 (Ref = 30-39 years) Average annual rate (cases / 100,000) 70 RR=4.6 Seasonal influenza (J10+J11) 60 Confirmed influenza (J10) 50 Pandemic influenza (J09) 40 RR=38.6 30 RR=6.7 20 RR=1.5 RR=4.3 10 RR=0.2 0 0-4 5-9 10-19 20-29 30-39 40-49 Age group (years) 50-59 60-69 70-79 80+ Risk factors Average annual rate (cases / 100,000) Influenza hospitalisation rate by ethnicity, Auckland 2000-08 (Ref = European/Other) 70 Seasonal influenza (J10+J11) 60 50 RR=7.1 Confirmed influenza (J10) Pandemic influenza (J09) 40 RR=3.6 30 RR=3.5 20 RR=1.6 RR=5.5 RR=1.7 10 RR=0.8 RR=2.2 RR=1.0 0 European/Other Māori Pacific Ethnic group Asian Risk factors Influenza hosp rate by deprivation, Auckland 2000-08 (Ref = NZDep 1-2) Average annual rate (cases / 100,000) 35 30 RR=3.2 Seasonal influenza (J10+J11) Confirmed influenza (J10) 25 Pandemic influenza (J09) 20 15 RR=3.3 10 RR=5.8 5 0 1-2 3-4 5-6 7-8 Deprivation quintile (NZDep 96) 9-10 = high deprivation 9-10 Risk factors Pandemic influenza rate ratios for outcomes by ethnic group, NZ 2009 (age & dep stand.) Risk-adjusted event rate ratio to European/Other rate 9 Consultations Other flu hospitalisations J09 hospitalisations ICU cases Deaths 8 7 6 5 4 3 2 1 1.00 1.00 1.00 1.00 1.00 0.88 1.74 2.44 2.01 1.14 0.90 2.21 4.16 5.03 3.28 0.72 0.60 0.98 0.77 0.76 European/Other Māori Pacific Asian 0 Ethnicity Risk factors Pandemic influenza rate ratios for outcomes by deprivation, NZ 2009 (age & ethnicity stand.) Consultations Other flu hospitalisations J09 hospitalisations ICU cases Deaths Risk-adjusted rate ratio to quintile NZDep 1-2 8 7 6 5 4 3 2 1 1.001.001.001.001.00 0.590.670.470.240.34 0.921.461.261.552.60 0.581.131.140.650.73 0.561.421.371.422.22 1-2 3-4 5-6 7-8 9-10 0 NZDep quintile Respiratory infections, NZ Hosp. rates for IDs vs. Non-IDs, 1989-2008 Hospitalisations per 100,000 people per year 8000 All-cause hospitalisations Non-infectious diseases 7000 6000 5000 4000 3000 2000 1000 0 Year Source: Baker et al 2012, Lancet in press Infectious diseases Respiratory infections, NZ Hospitalisations per 100,000 people per year Hospitalisation rates for ID categories, 2009 600 1989-1993 1994-1998 1999-2003 2004-2008 500 400 300 200 100 0 Blood Neurological Bone, Heart Neoplasms STIs Lower Skin and Enteric Digestive Genito- URTIs, Postrespiratory soft tract, urinary includingprocedure stream and eye joint, and from and ear and circulationinfection HIV tract tissue including liver connective tissues Infectious disease category Source: Baker et al 2012, Lancet in press Other Respiratory infections, NZ Hosp. SRR for IDs, by ethnicity, 1989-2008 Hospitalisation rate ratio to European & Other 2.50 European & Other (reference) 2.02 2.00 Māori 2.33 1.93 2.06 1.92 Pacific 2.35 2.15 1.77 1.50 1.00 0.50 0.00 1989-1993 1994-1998 1999-2003 Five-year period Source: Baker et al 2012, Lancet in press 2004-2008 Conclusions • Large differences in occurrence of serious influenza (hospitalised) across population groups ⇒ differences in risk factors • Relatively high rates of hospitalisation & serious outcomes for Māori and Pacific • Risk factors include: Exposure factors; Susceptibility factors; Progression factors • Some risk factors are modifiable ⇒ important to identify these • Small existing research base for seasonal influenza, some studies for pandemic influenza 2009 Discussion Points • What are ‘modifiable’ risk factors for influenza? • Do modifiable risk factors matter vs. increasing vaccine coverage? Acknowledgements • University of Otago: Jane Zhang, Lucy Telfar Barnard, James Stanley, Nick Wilson, and others • ESR: Sue Huang, Don Bandaranayake, Graham Mackereth and others • NZ Ministry of Health • US Centers for Disease Control and Prevention and NZ Health Research Council for funding support