Novel strategies to expand supply of yellow fever vaccine
A new special report commissioned and published by PATH concludes that delivering yellow fever vaccine at a reduced dose through a method referred to as dose-sparing could be a pragmatic and low-risk strategy for maximizing the availability of yellow fever vaccine.
The report, titled Yellow Fever Vaccination: The Potential of Dose-Sparing to Increase Vaccine Supply and Availability, finds that dose-sparing could help make more vaccine available in times of need, especially in mass immunization campaigns where supply shortages negatively impact human health.
Constrained vaccine supplies
Each year, yellow fever affects more than 200,000 people, with about 30,000 dying of the infection. Although there is no cure, the infection can be prevented with one dose of live attenuated yellow fever vaccine. Only four manufacturers currently produce yellow fever vaccines that have received prequalification status from the World Health Organization (WHO), allowing for the purchase and use of the vaccine by United Nations agencies. This can result in insufficient vaccine supply to compensate for problems or disruptions in vaccine production or to meet spikes in demand when outbreaks occur.
Addressing supply gaps
As part of PATH’s ongoing efforts to explore innovative ways to improve vaccine delivery in low-resource settings, the new report investigates the potential benefits, obstacles, and costs of dose-sparing for yellow fever vaccine. It also assesses to what extent different delivery routes and novel delivery devices, such as needle-free jet injectors, could help facilitate the implementation of dose-reduction strategies.
Among the key findings:
- Dose-sparing can induce levels of immunity comparable to a standard dose for some vaccines, including yellow fever vaccine, potentially helping to stretch limited supplies of existing vaccines.
- Dose-sparing could result in a fivefold increase in the number of vaccine doses per vial.
- Preventive yellow fever vaccination campaigns that include dose-sparing strategies could help conserve 24 to 42 million doses of yellow fever vaccine annually and up to 420 million doses by 2022—a savings of US$340 million in vaccine purchase costs over the next decade.
- To prevent vaccine wastage, dose-sparing strategies are likely to be more appropriate for immunization settings that involve a large number of vaccinations, such as preventive or outbreak-control campaigns.
- A reduced dose of yellow fever vaccine could potentially be administered through the intradermal and/or subcutaneous delivery route.
- Additional clinical trials are needed to confirm the safety and immunogenicity of reduced doses of yellow fever vaccines and to determine the best route of delivery.