Pneumococcal vaccine watches bacteria, strikes only when needed

Conventional vaccines indiscriminately destroy bacteria and other disease-causing agents. The approach works, but there is growing concern that it creates opportunity other pathogens to harm the body — similar to antibiotic resistance resulting in new and more potent pathogens. A new, protein-based pneumococcal vaccine takes a different approach. It allows pneumonia-causing bacteria to colonize in the body and — like a nightclub bouncer — swings into action only if the bacteria becomes harmful.