Background: New tuberculosis (TB) vaccines are being developed to combat the global epidemic. A phase
IIb trial of a candidate vaccine, MVA85A, was conducted in a high burden setting in South Africa to
evaluate proof-of-concept efficacy for prevention of TB in infants.
Objective: To describe the study design and implementation lessons from an infant TB vaccine efficacy
trial.
Methods: This was a randomised, controlled, double-blind clinical trial comparing the safety and efficacy
of MVA85A to Candin control administered to 4e6-month-old, BCG-vaccinated, HIV-negative infants at
a rural site in South Africa. Infants were followed up for 15e39 months for incident TB disease based on
pre-specified endpoints.
Results: 2797 infants were enrolled over 22 months. Factors adversely affecting recruitment and the
solutions that were implemented are discussed. Slow case accrual led to six months extension of trial
follow up.
Conclusion: The clinical, regulatory and research environment for modern efficacy trials of new TB
vaccines are substantially different to that when BCG vaccine was first evaluated in infants. Future infant
TB vaccine trials will need to allocate sufficient resources and optimise operational efficiency. A stringent
TB case definition is necessary to maximize specificity, and TB case accrual must be monitored closely