Strengthening New Vaccine Introduction in Low- and Middle-Income Countries: Establishing Hospital-Based Sentinel Surveillance for Vaccine Safety Monitoring.

Enhancing surveillance for adverse events following immunization remains a key global immunization priority. Many low- and middle-income countries (LMICs) are implementing new vaccines without the comprehensive safety monitoring typically conducted in high-income countries. Since 2017, the Global Immunization Safety Team at the US Centers for Disease Control and Prevention, in collaboration with partners, has supported establishing sentinel surveillance systems during vaccine introductions for safety monitoring in LMICs. Through these experiences, many lessons have been learned regarding project initiation, funding opportunities, standardizing data collection, background rate challenges, site selection considerations, and partner coordination. If vaccine safety is prioritized, sentinel surveillance enhances routine monitoring and generates valuable safety data, strengthening the immunization and regulatory programs. As many countries introduce and manufacture vaccines not previously monitored in high-income countries, lessons from safety monitoring during earlier vaccine introductions must be applied. Sustaining the gains in immunization that were hard-earned over the past decades depends on it.