Randomised trial of 23-valent pneumococcal capsular polysaccharide vaccine in prevention of pneumonia in middle-aged and elderly people. Swedish Pneumococcal Vaccination Study Group.

We assessed the effectiveness of a 23-valent pneumococcal vaccine in the prevention of pneumococcal pneumonia and of pneumonia overall in non-immunocompromised middle-aged and elderly people. The prospective, multicentre, double-blind, randomised, placebo-controlled trial was carried out across departments of infectious diseases at six tertiary-care or university hospitals in Sweden. 691 non-immunocompromised patients aged 50-85 years who had been treated as inpatients for community-acquired pneumonia (CAP) were randomly assigned either 23-valent pneumococcal capsular polysaccharide vaccine or placebo (sodium chloride). We used Cox regression models to estimate the relative risks of pneumonia overall and pneumococcal pneumonia for the placebo group compared with the vaccine group. 63 (19%) of 339 patients in the vaccine group and 57 (16%) of 352 patients in the placebo group developed a new pneumonia, corresponding to a relative risk over time for the placebo group compared with the vaccine group of 0.83 (95% CI 0.58-1.12, p=0.31). Pneumococcal pneumonia was diagnosed in 16 (4.5%) patients in the placebo group and in 19 (5.6%) in the vaccine group, corresponding to a relative risk for the placebo group of 0.78 (95% CI 0.40-1.51, p=0.45). We found no difference in the death rate between the two study groups. The 23-valent pneumococcal polysaccharide vaccine did not prevent pneumonia overall or pneumococcal pneumonia in middle-aged and elderly individuals.