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With the EYE campaign now running at full speed, the global vaccine supply could increase up to 175 million doses by 2025, Nguyen said. However, manufacturers are not currently able to meet that demand, according to a 2017 report from Gavi. The yellow fever vaccine market was deemed “in a low state of health” and may not be able to match demand in case of a serious outbreak. While the vaccine meets Gavi’s requirements for immunization, the agency is working with manufacturers on improving supply and procurement processes so as to increase global production.


Current vaccine production involves culturing the vaccine virus strain in chick embryos, a method that was developed in the 1930s. The process is efficient but resource-intensive, and limits the ability to manufacture doses at scale, meaning supply doesn’t always meet demand.


Sanofi is developing a new vaccine that uses a cell-culture technology, which has been shown to speed up, improve robustness, and simplify the manufacturing process. It can also be administered to populations with contraindications to the egg-derived vaccines, including people with severe allergies to egg proteins.

Lyophilisation
Val de Reuil, France - April 2011
Copyright: Sanofi Pasteur / Alexis Chezière

Yellow Fever vaccine manufacturing facility
Val de Reuil Sanofi Pasteur site, France, June 2013 Copyright: Sanofi Pasteur / Patrick Boulen

“The use of a modern approach such as Vero cell cultures will lead to greater production efficiency and will significantly contribute to the sustainability of this vaccine for all those who need it,” Sanofi’s Kester said.


The company’s new vaccine will ultimately replace the two vaccines it currently distributes. Having a single vaccine will help Sanofi respond to demand more efficiently, according to Kester. The new manufacturing process will also make it possible to increase production capacities in a shorter time frame so that global demands are better met, either for routine immunization or for outbreak response.


If the stockpile were to be depleted during future outbreaks, WHO would divert doses from preventive campaigns and revert to using fractional doses again, according to Gavi documents. Additional studies will provide more evidence regarding the long-term effectiveness of fractional doses, but this might threaten the integrity of the vaccine, Kester said. Sanofi follows a multiyear review process to secure government approval for specific uses of the vaccine, and fractioning isn’t one of them, he added.


“We respect WHO's position, especially in the context of an outbreak or when there's limitations on the global stockpile,” Kester said. “But it represents an off-label use, and as a company, we have to adhere to how our products have been approved. For a company to talk about their products in an off-label manner really goes against the whole regulatory paradigm.”

“The use of a modern approach such as Vero cell cultures will lead to greater production efficiency and will significantly contribute to the sustainability of this vaccine for all those who need it,” Sanofi’s Kester said.


The company’s new vaccine will ultimately replace the two vaccines it currently distributes. Having a single vaccine will help Sanofi respond to demand more efficiently, according to Kester. The new manufacturing process will also make it possible to increase production capacities in a shorter time frame so that global demands are better met, either for routine immunization or for outbreak response.


If the stockpile were to be depleted during future outbreaks, WHO would divert doses from preventive campaigns and revert to using fractional doses again, according to Gavi documents. Additional studies will provide more evidence regarding the long-term effectiveness of fractional doses, but this might threaten the integrity of the vaccine, Kester said. Sanofi follows a multiyear review process to secure government approval for specific uses of the vaccine, and fractioning isn’t one of them, he added.


“We respect WHO's position, especially in the context of an outbreak or when there's limitations on the global stockpile,” Kester said. “But it represents an off-label use, and as a company, we have to adhere to how our products have been approved. For a company to talk about their products in an off-label manner really goes against the whole regulatory paradigm.”