Projecting vaccine demand and impact for emerging zoonotic pathogens

Area of Science:

• Epidemiology
• Public Health
• Vaccinology

Background:

• Several zoonotic pathogens pose a threat due to their epidemiological characteristics and evolutionary potential.
• The Coalition for Epidemic Preparedness Innovations is developing vaccines for WHO-priority pathogens.
• A key challenge is anticipating vaccine stockpile demand for outbreak response.

Purpose of the Study:

• To develop a modeling framework for outbreak response for emerging zoonoses.
• To assess sustainable vaccine manufacturing needs and stockpile requirements.
• To evaluate the potential impact of reactive vaccination strategies.

Main Methods:

• Developed a modeling framework incorporating geographically variable zoonotic spillover, human-to-human transmission, and reactive vaccination.
• Applied the framework to Lassa virus, Nipah virus, MERS coronavirus, and Rift Valley fever virus.
• Assessed three reactive vaccination strategies: population-wide, ring vaccination, and targeting healthcare workers (HCWs).

Main Results:

• Annual vaccine needs for population-wide strategies ranged from over 670,000 to 1.19 million regimens.
• Ring vaccination or targeting HCWs required significantly fewer vaccine regimens (several orders of magnitude lower).
• Targeting HCWs demonstrated a higher per-regimen impact on preventing cases compared to population-wide vaccination.

Conclusions:

• The developed framework aids in estimating vaccine stockpile needs and demand distribution for outbreak response.
• Identified knowledge gaps in surveillance, spillover routes, and human-to-human transmission are critical for accurate targeting.
• Pathogen evolution could necessitate adjustments to vaccine stockpile requirements, highlighting the need for adaptable strategies.