Public Health Interventions: lessons learned

Mark Loeb MD, MSc

McMaster University

Public Health Interventions Influenza (H1N1) 2009

• Non-pharmacologic interventions - school closure, quarantine - PPE • Pharmacologic interventions

- targeted use of anti-virals - uptake and effectiveness of vaccination

MMWR July 30, 2010

Context • 2009 H1N1 pandemic less virulent than expected, plans

based on previous assumptions had to be rethought

• Interventions previously planned had to be reassessed

• Tension between the urgent need to collect and understand information and the need to take immediate action

• Because implementation takes place at the local level, it had to be adapted to local capabilities and existing systems.

Pandemic influenza as 21th century urban public health crisis

Mexico City NYC Shared Elements

Initial appearance

National surveillance

School introduction

Core activities:

Intensive, multi-faceted mediaCampaign

Novel syndromic surveillance developed pre-pandemic were activated

Coordination of government at different levels; collaboration of public health and emergency response

Promotion of personal hygiene

Extensive public communications campaign via pre-existing program

Surveillance a function of organization and provision of health services

Extensive social distancing, wide spread school closures

Selective school closure Criteria for re-opening schools were unclear

Bell DM et al. Emerg Infect Dis 2009; 15:1963 - 1969

School Closure and Mitigation of Pandemic (H1N1) 2009, Hong Kong

Wu JT et al. Emerg Infect Dis 2010; 3:538-541

Quarantine Methods and Prevention of Secondary Outbreak of Pandemic (H1N1) 2009

Chu CY et al, Emerg Infect Dis 2010; August

N95 respirators vs Surgical Masks pH1N1

• Considerable uncertainty about the effectiveness of personal respiratory devices against pH1N1

• In the inter-pandemic setting, surgical masks, which filter large droplet particles, are recommended for HCWs

• For H1N1, recommendations vary from uniform use of N95 (CDC) to N95 use restricted to aerosol generating procedures (WHO)

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Surgical Masks to protect HCWs against pH1N1

Figure 1.  Weekly number of confirmed cases of pandemic novel swine‐origin influenza A (H1N1)–2009 among patients and health care workers (HCWs) at Tan Tock Seng Hospital, Singapore, 26 April–31 August 2009.

Summary of the Four Outbreaks of 2009 H1N1 Influenza and Efficacy Prophylaxis and Other Interventions

Lee VJ et al. N Engl J Med 2010;362:2166-2174

Oseltamivir Ring Prophylaxis for Containment of 2009 H1N1 Influenza Outbreaks

Lee VJ et al, NEJM 2010: 362;2166-74

Phylogenetic Relationships among the Viruses Identified during the Four Outbreaks with the Use of Whole-Genome Sequencing

Lee VJ e Lee VJ et al, NEJM 2010: 362;2166-74 t al. N

Oseltamivir Ring Prophylaxis for Containment of 2009 H1N1 Influenza Outbreaks

Uptake of Influenza A (H1N1) 2009 Monovalent Vaccine: MMWR 2010 Apr 9(13)397

• Median 37% (21% to 85%) children aged 6 months to 17 yrs

• 33% (19% to 56%) for ACIP target groups by state

• Median 25% (10% to 47%) for adults 25 to 64 years at high risk

Public’s Response to 2009 H1N1 influenza Pandemic

Steelfisher GK et al. NEJM 2010; 362: e65

Interim Results: Influenza A (H1N1) 2009 Monovalent and Seasonal Influenza Vaccination Coverage Among Health-Care Personnel — United States, August 2009–January 2010

MMWR 2010 Apr 9;59 (13)397

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Nolan, T. et al. JAMA 2010;303:37-46.

Immune Responses After the First and Second Vaccinations With 2009 Influenza A(H1N1) Vaccine as Measured by the Hemagglutination Inhibition (HI) Assay

Pandemic Influenza Breakthrough infections and estimates of vaccine effectiveness in Germany 2009-2010

Wichmann et al, Euro Surveill 2010; 15 (18); 19561

Vaccine effectiveness in pandemic influenza – primary care reporting (VIPER): an observational study to assess the effectiveness of the pandemic influenza A (H1N1)vaccine

• Study from Scotland, retrospective cohort design• Network of 41 general practises (250,000

patients), n=59, 712• Linked medical records data with laboratory

testing H1N1 (October to December 2009)• 1,492 swabs (only 1 vaccinated was positive)• Report 95% effectiveness (95%CI 76% to 100%) of

H1N1 vaccine in high priority groups

Simpson et al, Health Tech Assess 2010; 14: 3131-346

Hutterite Cluster RCT

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Loeb, M. et al. JAMA 2010;303:943-950.

Flow Diagram of Trial

RCT – Year 2 Data• Follow up from November 2009 to May 2010• N=3840• 14 day post vaccine analysis• 1077/3840 (28%) = H1N1 vaccine• 54 cases of H1N1 (PCR confirmed) - 1/1072 or 0.1%(H1N1 vaccine) - 53/2768 or 2% (No H1N1 vaccine)

Vaccination and H1N1 (2009) InfectionMonovalent vaccine

n=1071

No monovalent vaccine

n=2715

P Value

Protective Effectiveness

Participants with H1N1 (2009) influenza detected by RT-PCR– no.(%)*

1 (0.1%) 53(2%) 95% (65% to 99%)0.003

SeasonalVaccine

n=994

No seasonalVaccine

n=2846

HR (95% CI)

Participants with H1N1 (2009)Detected by RT-PCR – no. (%) 17 (1.7%) 37 (1.3%) 1.36 (0.74-2.34) 0.35

Summary

• Selected nonpharmacological interventions appear to be have had an effect

• Ring prophylaxis (military setting) highly effective

• Early data support effectiveness of the monovalent vaccine

• Need improvement on vaccine uptake in both community and healthcare settings