Acute respiratory infections, often due to Streptococcus pneumoniae (pneumococcus), are a primary cause of death in young children in developing countries. A new vaccine effectively prevents the most serious form of pneumococcal disease and also reduces nasopharyngeal colonization with pneumococci. Because only some people who are infected become ill, researchers must study tens of thousands of vaccinated individuals over a long period of time to determine whether the vaccine guards against disease.  The cost and complexity involved in estimating the effectiveness of the vaccine has become a major roadblock to wide use of the vaccine in developing countries.

Dr. Käyhty is leading an international consortium of investigators whose goal is to establish a quick and inexpensive method of determining the efficacy and expected effectiveness of the pneumonia vaccine. Each of the consortium's nine collaborative institutions brings with it data collected in previous trials as well as ongoing studies conducted in ten locations all over the world. The team is aiming to establish reduction of colonization with the pneumonia bacteria as part of the licensure pathway.
 
The consortium's investigators plan to use the model of colonization derived from existing data to guide the method of determining vaccine efficacy for colonization (VE-col). They will estimate VE-col using data derived from several studies conducted in different geographical locations and determine the serological correlates of protection for several of the most common serotypes. A simulation model of pneumococcal transmission will be developed to demonstrate the effectiveness of vaccine in different epidemiological settings.

At the end of the project, investigators hope to offer two alternative tools for determining VE-col: one directly measuring effects on colonization and the other through serological correlates of VE-col. The project will also provide guidelines for the use of these tools to assess different vaccine formulations, dosing, schedules, and programs in target populations.