Purpose: To study the efficacy of pneumococcal capsular polysaccharide vaccine among the elderly by use of a population-based intervention in one township, Varkaus, Eastern Finland.
Patients and methods: A randomized, controlled trial in which elderly inhabitants (aged 60 years or older) of the catchment area were randomized to receive either pneumococcal and influenza vaccines (PI group = vaccinated) or influenza vaccine alone (I group = controls) and offered participation. The response rate was 67.4%. The PI group consisted of 1,364 persons and the I group of 1,473 persons. The vaccinations were performed in the municipal health center in the fall of 1982, and all elderly inhabitants were followed for 3 years for the development of radiologically confirmed pneumonia. Pneumococcal etiology was identified by serological methods.
Results: The incidence of pneumonia was 18.8 per 1,000 person-years in the PI group (73 pneumonia episodes) and 16.6 per 1,000 person-years in the I group (69 episodes). Pneumococcal etiology was found in 27 episodes in the PI group (incidence 7.0 per 1,000 person-years) and in 36 episodes in the I group (incidence 8.6 per 1,000 person-years). In controls (I group) the incidence of pneumococcal pneumonia was significantly higher among persons with increased risk for contracting pneumonia (19 per 1,000 person-years) than among controls with low risk status (4 per 1,000 person-years). No significant protection from pneumococcal pneumonia was found in the study group as a whole (vaccine efficacy 15%, 95% CI -43% to 50%). However, in persons with medical risk factors for contracting pneumonia, there was a statistically significant protective efficacy of 59% (95% CI, 6% to 82%).
Conclusion: Pneumococcal vaccination significantly reduced the incidence of pneumococcal pneumonia in elderly persons at increased risk for contracting pneumonia. This increased/high-risk category comprised 34% of the population aged 60 years or older. Because targeted vaccination of this large group may be difficult to organize in an efficient manner, vaccinating all elderly persons may be the best strategy to prevent this rather common and often fatal disease.