WHO Prioritizes Endemic Pathogens for Vaccine Development

Vaccine development is traditionally driven by financial return opportunities for investors, disease outbreaks, and a specific focus on emerging diseases. However, a new systematic, transparent, and inclusive approach aims to prioritize pathogens based on socioeconomic and public health criteria.

A team led by the World Health Organization (WHO), with funding from the Bill & Melinda Gates Foundation, has published a list of endemic pathogens for which new vaccines are urgently needed.

Inclusive Methodology

The initiative involved policymakers, healthcare professionals, and public health and immunization experts. Factors considered included regional disease burden, socioeconomic impacts, and epidemiological differences between regions.

The list comprises 17 priority pathogens, with five classified as priorities in all regions and six identified as critical in specific areas. This approach ensures that pathogens with a significant regional health impact are not overlooked, even if they do not pose a global threat.

In the consensus view of the leaders of the Regional Immunization Technical Advisory Groups, which have been established in each of the six WHO regions, “The methodology applied ensures that these priorities reflect not only burden in terms of cases and deaths but also the values of stakeholders in different settings with respect to impact of long-term sequelae on quality of life, contribution to inequity and the broader socioeconomic toll of a pathogen. The approach is a departure from the conventional ‘top-down’ prioritization largely driven by the interests of people from high-income countries.”

Pathogen List

The WHO grouped pathogens on the basis of their stage of research and development (R&D), regulatory status, and feasibility of vaccine or monoclonal antibody development:

Vaccine Research Needed

• Group A streptococcus
• Hepatitis C virus
• HIV-1
• Klebsiella pneumoniae

Vaccines Needing Accelerated R&D

• Cytomegalovirus
• Influenza virus (broadly protective vaccine)
• Leishmania spp.
• Non-typhoidal Salmonella
• Norovirus
• Plasmodium falciparum
• Shigella spp.
• Staphylococcus aureus

Vaccines Nearing Regulatory Approval or Introduction

• Dengue virus
• Group B streptococcus
• Extraintestinal pathogenic Escherichia coli
• Mycobacterium tuberculosis
• Respiratory syncytial virus

Among the factors considered in the analysis were the contribution to antimicrobial resistance (AMR), highlighting the growing recognition of the role of vaccines in reducing the burden of AMR.

Leaving No One Behind

Regional lists were developed before consolidating the 17 global priorities. This process ensured evidence-based decisions that reflect the unique challenges faced by different areas.

Prioritization is essential for the efficient use of limited resources, and this list complements previous work by the WHO that identified priority pathogens with potential to cause future epidemics or pandemics.

This latest initiative, the “Immunization Agenda 2030”, is described by the WHO team as a global strategy aiming “to leave no one behind,” based on the principles of being data-driven, people-centered, partnership-based, and country-owned.

After an initial review that identified more than 150 potential pathogens for vaccine R&D, 26 were selected based on inclusion and exclusion criteria. Only those that cause diseases in humans, against which vaccines or monoclonal antibodies are in clinical development, and for which vaccine R&D is needed on the basis of specific disease control strategies, were considered. Additionally, pathogens recommended by regional WHO advisors were included.

Policymakers and immunization stakeholders from each WHO region were called upon to evaluate eight prioritization criteria. Experts identified the factors they considered most relevant when deciding which vaccines to introduce and use.

Eight Prioritization Criteria:

1. Annual deaths in children under 5
2. Annual deaths in people older than 5
3. Years lived with disability
4. Social and economic burden per case
5. Disruption due to outbreaks and epidemics
6. Contribution to inequality
7. Contribution to AMR
8. Unmet needs for prevention and treatment

For each criterion, five levels of evaluation were established, ranging from very low to very high. For example, the criterion “contribution to inequality” was rated very low if it affected all communities equally, while it was considered very high if the burden fell primarily on socially and economically disadvantaged groups, such as women.

Analysis of these preferences, combined with regional data for each pathogen, resulted in the top 10 priority pathogens for each WHO region. The regional lists were then consolidated into the global list, resulting in 17 priority endemic pathogens for which new vaccines need to be researched, developed, and deployed.

Limitations and Challenges

The initiative is not without its challenges and limitations. Not all countries participated. From the Americas, only half (51%) of the countries responded: Argentina, Bahamas, Barbados, Bolivia, Brazil, Canada, Chile, Colombia, Cuba, Ecuador, El Salvador, Guatemala, Guyana, Jamaica, Mexico, Peru, Suriname, and the United States.

Additionally, the data are based on the 2019 Global Burden of Disease Study, which does not account for the impacts of COVID-19 or recent increases in dengue cases.

This story was translated fromMedscape’s Portuguese edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.