Public Health Interventions: lessons learned Mark Loeb MD, MSc McMaster University
Dec 17, 2015
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
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)
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
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
Copyright restrictions may apply.
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
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