Pneumovax vaccination. Nurse injecting a patient with a dose of Pneumovax (pneumococcal polysaccharide vaccine). This contains inactivated extracts from 23 of the most common types of Streptococcus pneumoniae bacteria, the bacteria most commonly responsible for causing diseases such as pneumonia, blood poisoning and meningitis. This vaccine is given to the elderly and those with long-term health problems most at risk from such diseases.