Near real-time surveillance of vaccine and drug safety allows for rapid agency response and increased consumer protection, but inherent delays in data acquisition create challenges in rapid monitoring. The Updating Sequential Probability Ratio Test (USPRT) adapts empirical methods linked to the sequential probability ratio test to account for these delays. For three years the FDA has applied the USPRT to Medicare claims data for surveillance of the influenza vaccine by analyzing rates of Guillain-Barre syndrome in 15 million vaccinated beneficiaries annually. The USPRT allows for surveillance of the influenza vaccination as claims are processed, so the FDA can track vaccine-related complications and respond during the vaccination season. In future years the USPRT will be used to track several possible vaccine-related adverse events and adapted for use in prescription drug surveillance.