Should we develop an inhaled anti-pneumococcal vaccine for adults?

Streptococcus pneumoniae is the most important bacterial cause of pneumonia and meningitis among adults. It is also a common cause of bacteraemia among HIV infected adults with rates of disease approaching 100 times normal community incidence figures. Rates of antibiotic resistance are rising among pneumococcal isolates globally and the currently available 23-valent pneumococcal polysaccharide vaccine is ineffective in HIV infected adult populations. The newer conjugate vaccine has been highly effective in children in the developed world. It may also offer some promise in adult risk populations, but it is expensive and has limited serotype coverage. This article reviews the epidemiology of pneumococcal disease, the current state of pneumococcal vaccines, the pathogenesis of pneumococcal disease, the potential advantages of an inhaled vaccine in adults and some of the chemical obstacles to producing such a vaccine.