The Japanese 23-valent pneumococcal polysaccharide vaccine randomized clinical trial: Further reflections on the design and results

The recent article by Gessner et al. discussed several concerns regarding the design and results of the clinical trial by Maruyama et al. in 2010 on the vaccine efficacy (VE) of 23-valent pneumococcal polysaccharide vaccine. First, Gessner et al. questioned the integrity of the study randomization and blinding. Maruyama et al. have indicated that study participants were individually randomized and blinding was maintained throughout the study. Second, Gessner et al. questioned the internal validity of the trial results. Gessner et al. applied the reported VE against pneumococcal pneumonia and assumptions to estimate how much all-cause pneumonia could be prevented resulting in a "VE" estimate of 19.5%. This estimate does not truly qualify as a VE estimate, but as vaccine effectiveness estimate from a hypothetical cohort. The randomized, placebo-controlled trial conducted by Maruyama et al. met the methodological standards for a randomized control trial and its results are unquestionably valid.