660. Are US Clinicians Thinking Measles in the Post-elimination Era? Surveillance for Measles-Like Illness in a Commercially Insured US Population

Background In September 2016, the Americas was the first region to eliminate measles, a highly contagious, vaccine-preventable disease that can lead to complications and death. To maintain elimination, the Pan American Health Organization (PAHO) suggested a minimum rate of suspected measles investigations (≥2 per 100,000 population) be conducted annually. However, measles-like illness (MLI) investigations conducted by US clinicians are not tracked by the measles surveillance program in the United States. To ensure the US meets PAHO standards, we estimated the rate of MLI investigations using a large insurance claims database. Methods We used the 2009–2016 Truven Health MarketScan® Databases to identify MLI and MLI investigations. MLI were defined using International Classification of Diseases (ICD)-9/10 diagnostic codes in two ways: a priori, using the Council of State and Territorial Epidemiologists (CSTE) measles case definition or empirically, using ICD codes on insurance claims with a measles diagnostic code. MLI investigations were defined as MLI occurring up to 5 days prior to a measles diagnostic code or billing code for measles serology testing. We computed annual rates of MLI investigations per 100,000 population. Results We identified ~35.5 million MLI using the a priori definition. Of these, 24,010 had a measles serology code within 5 days; median age was 30 and 51% were aged 18–34 years. Using the empirical definition we identified ~46 million MLI. Of these, 29,940 were coupled with a measles serology code; median age was 31 and 50% were aged 18–34 years. The median annual rates for MLI investigations were 3.2 (a priori) and 4.3 (empirical) per 100,000 population. Conclusion Maintaining measles elimination requires continued vigilance by clinicians and high-quality case-based surveillance. The estimated rates of MLI investigations in this US population exceeded the PAHO standard, suggesting that the quality of US measles surveillance is robust. Disclosures All authors: No reported disclosures.