Hausdorff, William PHanage, William2016-11-182016Hausdorff, William P., and William P Hanage. 2016. “Interim results of an ecological experiment — Conjugate vaccination against the pneumococcus and serotype replacement.” Human Vaccines & Immunotherapeutics 12 (2): 358-374. doi:10.1080/21645515.2015.1118593. http://dx.doi.org/10.1080/21645515.2015.1118593.2164-5515http://nrs.harvard.edu/urn-3:HUL.InstRepos:29408351Streptococcus pneumoniae has more than 95 serotypes, each of which presumably can cause sepsis, meningitis, pneumonia, and acute otitis media. Pneumococcal conjugate vaccines (PCV) targeted against a limited number of serotypes have nonetheless revealed an impressive impact on each manifestation of pneumococcal disease. At the same time, growing evidence of significant non-vaccine type (NVT) replacement disease following implementation of infant PCV programs has raised questions about the long-term viability of PCV immunization strategies and how to optimize PCV formulations. We discuss here theoretical and practical considerations regarding serotype replacement, and provide a snapshot of the most important NVT types seen to date after implementation of the 2 higher-valent PCVs.en-USStreptococcus pneumoniaePneumococcal conjugate vaccinesInvasive Pneumococcal DiseaseSerotype replacementMeningitisAcute Otitis MediaJournal Article2016-11-1810.1080/21645515.2015.1118593