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VRBPAC November 2012 Joseph Bresee Epidemiology and Prevention Branch Influenza Division

Measurement of vaccine effectiveness against pandemic influenza vaccine: CDC perspective. VRBPAC November 2012 Joseph Bresee Epidemiology and Prevention Branch Influenza Division National Center for Immunization and Respiratory Diseases CDC. Review of human H5N1 Cases.

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VRBPAC November 2012 Joseph Bresee Epidemiology and Prevention Branch Influenza Division

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  1. Measurement of vaccine effectiveness against pandemic influenza vaccine: CDC perspective VRBPAC November 2012 Joseph Bresee Epidemiology and Prevention Branch Influenza Division National Center for Immunization and Respiratory Diseases CDC

  2. Review of human H5N1 Cases May - Dec. 1997, Hong Kong: 18 cases, 6 deaths Jan - Feb. 2003, Hong Kong: 2 cases, 1 death November 2003 to present: 608 confirmed cases (15 countries)* 359 deaths (59% mortality) Sporadic cases (children, young adults) Wintertime seasonality – poultry and human cases Risk factors Direct/close contact with sick/dead poultry Visiting a live poultry market Some cases without identified exposure source Late presentation/hospitalization/delayed treatment Case clusters Most are due to poultry exposures Limited human-to-human H5N1 virus transmission 2nd generation (most clusters) Two clusters of 3rd generation transmission (Pakistan, Indonesia) Ungchusak et al., NEJM 2005; Kandun et al. NEJM 2006; Wang et al., Lancet 2008; WER 2009; WHO, unpublished data *Reported to WHO as of August 10, 2012

  3. Human H5N1 Cases Reported to WHONov. 2003 - 2012 (N = 608; 15 countries)

  4. 2012 Human H5N1 Cases* N = 30 cases (6 countries) Egypt (10) Indonesia (8) Cambodia (3) China (2) Vietnam (4) Bangladesh (3) 37.5% fewer infections than in 2011 (Jan-Sept) Case fatality proportion: 63% (19/30) Median age overall: 22 years (range: 1 - 45 years) [n = 23] *Reported to WHO as of August 10, 2012

  5. Number of H5N1 human cases reported to WHO 55 45 Entire 2011 35 Jan-Aug 2012 25 15 5 48 63 Fatality 38 50 83 100 0 0 0 50 100 50 100 100 -5 Rate Egypt Indonesia Cambodia Bangladesh Viet Nam China/HK(SAR) Total Geographic distribution of H5N1 human cases since January 2012 China/HK(SAR) clade 2.3.2.1, 2.3.4.2 Bangladesh Egypt Clade 2.2.1 Clade 2.3.2.1 Cambodia Vietnam Clade 1.1 Clade 1.1 Indonesia Clade 2.1.3.2 Countries reporting human H5N1 cases Provinces with human H5N1 Source: WHO, CDC

  6. Summary • Epidemiology and clinical characteristics largely unchanged in recent years • Sporadic human illness caused by infection with HPAI H5N1 virus continues to occur and be identified • Children, young adults • Exposure to sick/dead poultry continues to be major risk factor • Seasonality continues (colder periods) • Relatively fewer cases in 2012 compared previous years • Confirmed cases are an underestimate of human H5N1 virus infections • Risk remains • Humans exposed, especially in endemic countries • Viruses continue to evolve

  7. CDC’s Vaccine Effectiveness Program

  8. CDC’s Influenza Division program to measure influenza vaccine effectiveness in the U.S. 6 – 59 mo. OP, Hosp. Adults >18 y Hosp. Adults > 50 y Hosp. 6–59m Hosp. 6 – 23 m Hosp. New Vaccine Surv. Network Emerging Infections Program Special studies US VE Network - 2 US VE Network - 1 ACIP recommended groups MAARI Marshfield Clinic, WI ACIP recommended groups - MAARI All Ages MAARI School HCWs, Peds. ICU, Pregnant Household VE 04-05 03-04 05-06 06-07 07-08 08-09 09-10 10-11 11-12 12-13 Influenza season

  9. US Flu VE Network • Purpose • Estimate VE for prevention of healthcare visits due to influenza, by age group and type/subtype • Not designed to develop product-specific estimates Sites Five medical systems and geographic regions: • Group Health Cooperative (WA) • Marshfield Clinic (WI) • Scott & White Healthcare (TX) • University of Michigan (MI) • University of Pittsburgh (PA) EnrolleesChildren and adults with medically attended acute respiratory illness (MAARI)

  10. US Flu VE networkMethods • Design: Prospective case-control study • Cases: MAARI with RT-PCR influenza • Controls: MAARI but negative for influenza • Vaccination status: confirmation through record review pending • Immunization: defined by receipt of at 1+ dose of vaccine 14 or more days before onset of respiratory symptoms • Analysis: VE = (1-adjusted OR) x 100%, estimated with logistic regression models, with assessment for potential confounding by • age, sex, race, ethnicity • date of symptom onset • days between symptom onset and testing for influenza • insurance status, self-reported health status • Self-report of medical conditions that increase the risk of influenza-related complications

  11. US Flu VE Network2011-12 Results, overall and type/subtype Unpublished data, CDC

  12. US Flu VE Network2011-12 results, by age group Unpublished data, CDC

  13. US Flu VE Network Evaluating monovalent H1N1 vaccine effectiveness during the pandemic, 10/2009 – 04/2010 Adjusted pandemic vaccine effectiveness for all four licensed vaccines and for all ages combined was 56% (95% CI = 23%-75%) --low numbers prevented demonstrating significant protection for many subgroup analyses (age, vaccine type) Griffin, M et al. (2010) . Plos ONE 6 (8): e23085

  14. Emerging Infections Program Influenza Surveillance • Population-based surveillance for laboratory-confirmed influenza-associated hospitalizations • Children (<18 years) and adults • Current network covers • 10 states: CA, CO, CT, GA, MD, MN, NM, NY, OR, and TN • Represents ~7% of the US population • Conducted studies to measure VE for influenza-positive hospitalizations from 2005-2011 • By age groups

  15. Estimating VE against hospitalizations in EIP during the pandemic, 2009-2010 EIP Adult H1N1 Hospitalizations Successful in calculating significant and consistent overall VE Low enrollment limited ability to estimate VE among subgroups (or vaccine types) Average enrollment start date (≥10% vaccine coverage)

  16. Maine School-Located Influenza Vaccination Campaign during the 2009 HIN1 pandemic • Maine distributed most of their 2009 H1N1pdm MIV through school-located influenza vaccine campaigns • US CDC and Maine CDC collaborated on a state-wide evaluation of VE against absenteeism • VE was 33% (95% CI = 26-40) against absences of 3+ days a • VE against lab-confirmed influenza in Cumberland county • VE was 69% (95% CI = 12-89) b (a) Graitcer, SB et al. (2012) . Vaccine 30: 4835-4841.. (b) Uzicanin, A et al. (2012) . JID 206: 1059-1067

  17. Respiratory Virus Circulation and 2009 H1N1pdm MIV Uptake, Maine, 20092010

  18. Key points related to Influenza Vaccine Effectiveness Program at CDC • Robust system for measuring VE • Most seasons, able to estimate overall VE as well as age group-specific VE • Able to formulate rapid (intra-season) VE estimates • Important for seasonal and pandemic communications • Geographically dispersed sites – so mitigates risk of geographic variability in disease occurrence • During 2009 H1N1 pandemic • Sites mobilized quickly and effectively despite early onset of disease • Able to initiate special project to address VE in specific populations to augment understanding of vaccine performance • Late arrival of vaccine compared to disease limited ability to conduct subgroup analyses

  19. Can the US VE system measure product-specific VE during a pandemic? Limitation: • Temporal overlap between disease and vaccination will limit power Attribute: • Robust system for measuring VE – so, with high AR, can get VE • High mortality associated with H5 pandemic may reduce ability to fully mobilize sites • Mobilized US VE sites and other platforms for 2009 H1N1 pandemic successfully • Geographic location of sites might not reflect distribution of product in a way that makes product VE estimates possible • Geographically dispersed sites – so should capture cases • Currently, 30% of product information is left blank, reducing power to address this question • Capture vaccine product information

  20. Conclusions • CDC plans to estimate overall and age-group-specific VE for pandemic vaccine during the next pandemic • Using existing seasonal VE program platforms, primarily • CDC can’t guarantee that product-specific VE estimates will be derived from its work during the next pandemic • Sample size available: • number of sites/cases in current systems • late delivery of vaccines compared with disease • Limited ability to expand during a severe pandemic • Limited ability to maintain a larger system in advance of a pandemic • Human resource challenges during a severe pandemic • Distribution of vaccine products uncertain • Will continue to plan for pandemic VE work, and this conclusion could be modified in the future

  21. THANK YOU

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