First human challenge testing of a pneumococcal vaccine: Double-blind randomized controlled trial

Rationale: New vaccines are urgently needed to protect the vulnerable from bacterial pneumonia. Clinical trials of pneumonia vaccines are slow and costly, requiring tens of thousands of patients. Studies of pneumococcal vaccine efficacy against colonization have been proposed as a novel method to down-select between vaccine candidates. Objectives: Using our safe and reproducible experimental human pneumococcal colonization model, we aimed to determine the effect of 13-valent pneumococcal conjugate vaccine (PCV) on colonization. Methods: A total of 100 healthy participants aged 18-50 years were recruited into this double-blind randomized placebocontrolled trial. They were randomly assigned to PCV (n = 49) or hepatitis A (control, n = 50) vaccination and inoculated with 80,000 CFU/100 μl of Streptococcus pneumoniae (6B) per naris. Measurements and Main Results: Participants were followed up for 21days todetermine pneumococcal colonization by culture ofnasal wash. The PCV group had a significantly reduced rate of 6B colonization (10% [5 of 48]) compared with control subjects (48% [23 of 48]) (risk ratio, 0.22; confidence interval, 0.09-0.52; P < 0.001). Density of colonization was reduced in the PCV group compared with the control group following inoculation. The area under the curve (density vs. day) was significantly reduced in the PCV compared with control group (geometric mean, 259 vs. 11,183; P = 0.017). Conclusions: PCV reduced pneumococcal colonization rate, density, and duration in healthy adults. The experimental human pneumococcal colonization model is a safe, cost-effective, and efficient method to determine the protective efficacy of new vaccines on pneumococcal colonization;PCVprovides a gold standard against which to test these novel vaccines. Copyright © 2015 by the American Thoracic Society.