Pandemic influenza vaccine development: Status of

preparedness

Ruben Donis

Influenza Division, NCIRD, CCID, CDC

Pandemic Influenza Vaccines: Building a Platform for Global Collaboration

Beijing, China; January 28-30, 2007

Organizers and Sponsors

• Chinese Center for Disease Control and Prevention

• The National Bureau of Asian Research

• Bill and Melinda Gates Foundation

• Wellcome Trust

• Other partner organizations

Pandemic Vaccines: challenges and opportunities

• Challenges – Insufficient capacity to immunize the world population

• Opportunities– Strengthen virus detection– Increase vaccine production capacity by 6-fold– Deliver vaccines to everyone in a timely fashion– Develop improved vaccines

Immunization Strategies

• Non-replicating vaccines– Inactivated influenza virions

• Subviral (split) or whole virion• Produced in eggs or (soon) cell culture

– Recombinant expression systems• Baculovirus, insect cells, VLP (HA-NA-NP-M)

– Nucleic acid vaccines and Adenovirus vectors

• Replicating vaccines– Live attenuated cold-adapted strains

• Produced in eggs or (soon) cell culture

– Viral vectored: alphavirus, flavivirus, paramyxovirus

Licensed in USA for use as Seasonal Vaccines

Immunization Challenges

• Protective immunity induced by currently licensed vaccines is largely strain specific– Strain differences reduce vax efficacy– Vaccine stockpiles become obsolete– Prepare many homologous pandemic vaccines

• Challenge:• Broaden specificity of protective immunity

– Live and inactivated vaccines

Immunization Challenges

• Inactivated avian HA subtype vaccines appear to be poorly immunogenic in humans– Requiring 2 doses of 90 µg (6-fold > seasonal flu)– Adjuvants reduce the required dose increase

• Challenge:• Increase the immunogenicity of inactivated

vaccines – Develop adjuvants– Alternative immunogens or routes of delivery

Pandemic Vaccine Development Challenges

Pandemic Influenza (H5N1)

Pandemic Vaccine (H5N1)

Person-to-person Transmission

Immunity to Influenza (H5N1)

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Surveillance Challenges

• Virologic surveillance is critical – Strengthen PH systems and laboratory support– Collaboration with animal health authorities critical– Rapid bedside pandemic flu diagnostics needed– Lab confirmation of all human cases

• Molecular methods: realtime PCR• Virus culture in BSL3

– Facilities: expand local BSL3 lab capacity

• Opportunities– Library of viruses for diagnostic and vaccine development– Expanded molecular databases– International sharing of strains and sequences is essential– WHO IHR recommendations in effect June 1 ‘07

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Vaccine Strain Selection

• Antigenic analysis of viral isolates– Resource intensive process– BSL3 enhanced facilities, personnel, ferrets– Panels of antisera to numerous virus strains

• Genetic characterization– Sequence analysis increasing rapidly– Public access to virus sequences is improving

• Genbank, LANL, BGI

• Challenge– Sharing reagents and sequences is critical– WHO International Health Regulations (IHR) buy-in

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Engineer Safe Vaccine VirusesReverse GeneticsEngineer Safe Vaccine VirusesReverse Genetics

9 days

High YieldAttenuated virus (PR8)

Virulent Hemagglutinin

High Yieldavirulent vaccineVero Cells

BSL3-enhanced virus

BSL2 virus

High Yield Reassortants by Reverse Genetics

• Work must be done in BSL3• HA modification required for BSL2 mfg

– 6:2 reassortants (PR8:H5N1) • RG Technically robust

– Applicable to inactivated and LAIV

• Challenges– Requires vaccine-certified Vero cells – Commercial use RG process is protected by

patents

CDC RG reassortant stocks

• 3 H5N1 candidate vaccines distributed by CDC• No fees charged to users

– A/Vietnam/1203/2004: Clade 1• 54 recipients

– A/Indonesia/5/2005: Clade 2.1• 49 recipients

– A/Anhui/1/2005: Clade 2.3• Collaboration with China National Influenza Center• 14 recipients in 1st quarter 2007

• MTA for RG required by Medimmune

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

a. Safety testing: permit to transfer from BSL3 into BSL2

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Transfer virus from BSL3 to BSL2

• USA HPAI is restricted to BSL3 by Dep't of Agriculture– “USDA Select Agent”

• Apply for permit to use RG vaccine reassortants in BSL2– Source of materials (viruses, plasmids, description of

modification)

– Sequence analysis of the HA gene • amino acid motif at the HA cleavage site

– Pathogenicity testing in chickens

– Plaque characterization on chicken embryo fibroblast (CEF) cells with or without trypsin

– With permit approval, all subsequent work done at BSL-2 level

RG Ressortant: WHO safety evaluation

• RG Reassortant Reference Stock– WHO Guidelines: Lack of pathogenicity

• Ferrets– Intranasal challenge: ≥ 6 logs– Level of virus replication and symptoms ~ PR8– No replication in brain tissue

• Mouse pathotyping optional• Chickens

– Intravenous pathogenicity test

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Egg-based production

• Supply of fertile eggs for vaccine– No surge capacity

• Production must be scheduled many months in advance

• FY04 HHS-CDC Contract Sanofi-Pasteur – Guaranteed production of fertile eggs for

vaccines

• Short term fix to secure a minimum of pandemic vax production

Pandemic Vaccine Manufacturers

• Australia– CSL

• Austria– Baxter

• Canada– ID-GSK

• China– Sinovac

• France– Sanofi-Pasteur

• Germany– GSK

• Italy – Chiron-Novartis

• Japan– Denka-Seiken, Kaketsuken,

Kitasato

• Netherlands– Solvay, Nobilon

• Switzerland– Berna

• UK– Chiron-Novartis

• USA– Medimmune, Merck, Sanofi,

Novartis

Egg production, source (partial listing)

Production Challenge

• Current annual total monovalent vaccine production capacity worldwide– 900-1,000 Million doses @ 15 µg/dose

• Sufficient for 15% of population (only one dose)• >5 years required to immunize everyone• Inactivated and live vaccines produced in eggs• Fertile egg supplies not likely to increase • Challenge

– New technologies are needed

Cell-based production

• Vertebrate cells used as substrate to propagate virus in large scale

• US HHS awarded ~ $1,000 million in FY06– Goal: Production capacity to deliver 600

million doses (@ 15 µg) in 6 months

• Awardees:• Baxter• GSK• MedImmune

• Novartis• Sanofi-Pasteur• Solvay

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Potency Evaluation

• Determine HA content in bulk vaccine– Required for formulation and dispensing

• Single Radial Immunodiffusion (SRID)– Homologous monovalent sheep serum

• Several weeks to develop and validate• Requires purified HA to immunize sheep

– Calibrated homologous antigen

• Challenge– Calibrated antisera and antigen made available quickly– Prevent duplication of effort

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Regulatory Compliance Challenges

• Food and Drug Administration, CBER– Licenses vaccines in USA

• Code of Federal Regulations• International Conference on Harmonization (ICH)

Guidelines• Cell substrates

– Vero cells

• FDA to view egg-based inactivated pandemic vaccine as strain change for seasonal flu

• No discrimination due to reverse genetics

Overview of Inactivated Pandemic Vaccine Production

1. Surveillance: access to viruses from patients at diverse locations

a. Knowledge of strains that infect humans

2. Antigenic analysisa. Identify the prevailing antigenic types, select representative

strain

3. Produce avirulent high-yield reassortant virus by reverse genetics

4. Manufacture vaccine in eggs5. Potency testing6. Regulatory approval7. Distribute vaccine public health & private networks

Distribution Challenges

• Timeliness– Pandemic modeling studies

• Speed of vaccine deployment may be as important as antigenic match

– USA: target capacity of 10 million doses/week• Germann et al. PNAS 103:5935; 2006

Pandemic Vaccines Development Timeline

21 z3 4 5 6 7 8 9 x y

RG reassortant

Safety

Large scale production in eggs

Working seed

Produce & Standardize Potency Reagents

Week

Formulate and fill

•Support cell culture-based vaccines

•Improve growth of pandemic candidate vaccines

•Improve methods and reagents

• Increase speed and reliability of RG system (Vero cell alternatives)

Sustainability Challenges

• Pandemic preparedness in year 2020– Political system fatigue– New initiatives are more appealing

• How to sustain pandemic preparedness?– Strengthen seasonal influenza control– Strengthen links with animal health control – Think beyond H5N1

• H9N2, H7N*, H2N2, etc remain a threat

• Global Platforms for Collaboration

Acknowledgements

• WHO GIP Surveillance Network• Catherine Gerdil, Sanofi Pasteur, France• Ervin Fodor, Cambridge, UK• Erich Hoffmann, (MedImmune) St. Jude, Memphis, USA• Yumi Matsuoka, ID, CDC• Kanta Subbarao, NIH• Alexander Klimov, ID, CDC• Jacqueline Katz, ID, CDC• Tim Uyeki, ID, CDC• Robin Robinson, HHS• Zhiping Ye, FDA• John Wood, NIBSC• David Swayne; USDA, ARS, Southeast Poultry Research Laboratory,

Athens, GA, USA Nancy Cox, IB, CDC• Many more….

Thanks!