The case for a typhoid vaccine probe study and overview of design elements

Area of Science:

• Infectious disease epidemiology
• Vaccinology
• Public health policy

Background:

• Advances in typhoid vaccines and potential Gavi support may enable introduction into national immunization programs.
• Current decisions are hindered by insufficient data on the true burden of typhoid fever in endemic regions.
• Existing surveillance challenges include limited access to care, diagnostic inaccuracies, and incomplete data on mortality and complications.

Purpose of the Study:

• To propose and outline a vaccine probe study approach for accurately assessing typhoid disease burden.
• To address limitations in current data collection methods, including syndromic surveillance and antibiotic resistance.
• To provide a framework for evaluating the impact of typhoid conjugate vaccines in diverse healthcare settings.

Main Methods:

• A cluster randomized trial design involving mass immunization across all age groups is proposed.
• Monitoring of various outcomes over a 4-year period.
• The primary outcome measure is the incidence of vaccine-preventable prolonged fever hospitalization.

Main Results:

• Sample size calculations indicate the feasibility of conducting such a study under reasonable assumptions.
• The proposed approach aims to provide more definitive disease burden information.
• This method accounts for underreporting and diagnostic limitations inherent in endemic settings.

Conclusions:

• The vaccine probe study offers a robust method to determine typhoid disease burden and inform vaccine policy.
• This approach can provide critical data for countries considering the introduction of typhoid vaccines.
• Accurate burden estimation is essential for maximizing the impact of public health interventions like vaccination.