Study subjects are selected according to inclusion criteria from a source population within the Sentinel Common Data Mode v5.0.1 (SCDM). The SCDM includes over 100 million individuals with 358 million person-years of observation time who are covered by Aetna, Anthem, Group Health Cooperative, Harvard Pilgrim Health Care, and HealthPartners. The time period assessed will be 1/1/2011 - 9/30/2015.