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2 Influenza Virus and Influenza Vaccines: A Primer
Pages 25-58

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From page 25...
... . Global health experts have long warned of the risks of influenza and the need for preparedness, not only for the seasonal influenza variants, but also for variants with the potential to cause a pandemic.
From page 26...
... . In this chapter, the committee provides an overview of seasonal and pandemic influenza viruses and the production platforms that manufacturers use today, as well as ones they may use in the near future, to produce both seasonal and pandemic influenza vaccines.
From page 27...
... Pandemic Viruses Pandemic influenza is a global outbreak that affects a much larger segment of the population than a normal influenza season. WHO considers a potential pandemic variant to be an influenza virus for which people have little or no immunity and that is capable of sustained human-to-human transmission.
From page 28...
... . While the pandemic caused fewer deaths than anticipated, it served as an alert for public health authorities about the challenges of new influenza viruses (Kaplan et al., 2013)
From page 29...
... : see Figure 2-1. The collaborating centers conduct advanced antigenic and genetic analyses that form the basis for WHO recommendations on the composition of a given year's seasonal influenza vaccine.
From page 30...
... . Other countries, such as those in the European Union, also have animal health surveillance systems in place (European Commission, n.d.)
From page 31...
... Figure 2-2 shows the timeline from surveillance and strain selection to availability of vaccines for seasonal influenza. TABLE 2-2 Stages of and Data for Seasonal Influenza Vaccine Development and Manufacturing Stage of Development Data Collected Strain Selection Data from the World Health Organization and the Global Influenza Surveillance and Response System based on global surveillance.
From page 32...
... . Pandemic Influenza Vaccines For previous influenza pandemics, researchers and vaccine manufacturers focused efforts on refining existing production platforms that balance speed and quality, with less emphasis on developing new platforms.
From page 33...
... VACCINE PRODUCTION Seasonal Influenza Vaccines Manufacturing vaccines requires complex and sophisticated production facilities that in turn require substantial financial investment to construct and maintain. Construction of new vaccine manufacturing facilities can cost upwards of $500 million (Plotkin et al., 2017)
From page 34...
... Manufacturers Seqirus Current Share of 85–90 percent 10–15 percent 1–2 percent U.S. Market NOTES: Based on influenza vaccines licensed for use in the United States.
From page 35...
... Together, these four facilities account for 5 percent of seasonal influenza vaccine production capacity. There are two licensed recombinant vaccines, manufactured by Sanofi Pasteur in China, France, Japan, Mexico, and the United States and by CPL Biologicals in India (Sparrow et al., 2021)
From page 36...
... VACCINE PRODUCTION PLATFORMS Egg-Based Vaccines Egg-based manufacturing is used to make two different types of seasonal influenza vaccines, one containing inactivated virus that is administered as an injection, the other using live attenuated, or weakened, virus that is administered by nasal spray. In the United States, the production process starts with the CDC or another GISRS laboratory creating candidate vaccine viruses (CVVs)
From page 37...
... , which are then grown in a BOX 2-1 Adjuvants for Influenza Vaccines Adjuvants are substances added to a vaccine to boost the immune response to the vaccine's antigens by improving the ability of the host immune system to recognize the administered antigen as foreign and respond to it. In the case of influenza vaccines, adjuvants are used to boost responses in populations with poor immune responses, including individuals who are immunosuppressed (Dikow et al., 2011; Yam et al., 2014)
From page 38...
... . Recombinant Vaccines Recombinant influenza vaccines are created synthetically.
From page 39...
... approval process, the European Medicines Agency took many years to approve its version of the vaccine. Novel Vaccine Platforms While the egg-based, cell-based, and recombinant vaccine platforms have proven sufficient for producing safe and effective influenza vaccines for both seasonal and pandemic influenza, research on other platforms continues.
From page 40...
... Moreover, the quality of the mRNA vaccines that were developed at a record pace bodes well for balancing the issue of speed versus efficacy. One potential issue for mRNA influenza vaccines could be their instability at ambient and refrigerator temperatures, as evidenced by the need to store the COVID-19 mRNA vaccines at below-freezing temperatures.
From page 41...
... , though prior exposure to the parent virus can attenuate that response. Currently, three different types of viral-vectored influenza vaccines are in clinical trials (Sebastian and Lambe, 2018)
From page 42...
... If seasonal influenza vaccines were seen as more effective in preventing serious illness and greater consideration
From page 43...
... . Producing seasonal influenza vaccines in LMICs is not usually lucrative because there is low demand.
From page 44...
... Bilateral Agreements Under bilateral agreements, governments can enter into advance purchase agreements with vaccine manufacturers to procure doses of a vaccine ahead of when they will be needed. Such agreements are legally binding FIGURE 2-4 Vaccine manufacturing network.
From page 45...
... . UNICEF has procured seasonal influenza vaccine in limited quantities and faces challenges meeting demand due to a lack of accurate demand forecasting within countries (see Chapter 4)
From page 46...
... Countries with no national manufacturing capacity may be at a significant disadvantage for procuring vaccines depending on whether they have sufficient resources to readily meet their needs through purchasing products from other countries. As of 2019, 80 percent of pandemic influenza vaccine manufacturing facilities were located in high-income countries, which have only 16 percent of the world's population (Sparrow et al., 2021)
From page 47...
... authority for licensing new vaccines and approving annual modifications to previously approved seasonal influenza vaccines. Guidance issued by CBER provides two pathways for approval of a new vaccine: a traditional biologics license application (BLA)
From page 48...
... license for an approved seasonal influenza vaccine and the manufacturing process used to make the pandemic vaccine is the same as for the approved seasonal vaccine, CBER will approve a product containing inactivated virus based on the hemagglutination inhibition antibody response, with the added requirement of a detailed post-marketing surveillance plan. Vaccines containing live attenuated virus can also use the hemagglutination inhibition antibody response, as well as alternative endpoints that assess other immunological processes that live attenuated viruses can activate.
From page 49...
... Limited manufacturing capacity of influenza vaccines in LMICs is a significant barrier to expanding vaccine access. Procurement mechanisms for influenza vaccines are relatively recent, as no influenza vaccines had obtained WHO prequalification prior to 2006.
From page 50...
... . Through GAP, pandemic and seasonal influenza vaccines gained WHO prequalification (Palkonyay and Fatima, 2016)
From page 51...
... 2021. "Needs in Influenza Vaccine Manufacturing Preparedness." NASEM Commit tee on Addressing Issues of Vaccine Distribution and Supply Chains to Advance Pandemic and Seasonal Influenza Preparedness and Response, Committee Meeting #1, Washington, DC, March 19, 2021.
From page 52...
... 2015. Report on the second WHO integrated meeting on development and clinical trials of influenza vaccines that induce broadly protective and long-lasting immune responses: Geneva, Switzerland, 5–7 May 2014.
From page 53...
... 2014. Seasonal and pandemic influenza vaccine: Demand, supply and vaccine availability.
From page 54...
... 2016. A decade of adaptation: Regulatory contributions of the World Health Organization to the global action plan for influenza vaccines (2006–2016)
From page 55...
... Report to the President on reengineering the influenza vaccine production enterprise to meet the challenges of pandemic influenza. Washington, DC.
From page 56...
... Seasonal influenza vaccine: Sup ply update. https://www.unicef.org/supply/media/5206/file/Seasonal-influenza-vaccine supply-note-September-2020.pdf (accessed October 1, 2021)
From page 57...
... 2021. Promising adjuvants and platforms for influenza vaccine development.


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