AbstractBackgroundGSK’s measles-mumps-rubella (MMR) vaccine is indicated for active immunization of individuals aged 12 months and older against these 3 serious illnesses. It is licensed in > 100 countries worldwide not including the US. In clinical trials, it elicited robust immune responses in children and was well tolerated. Monitoring the vaccine’s real-world safety profile in the general population continues, and rapid collection of data on its real-world use is a strength of passive safety surveillance. We provide an overview of the postmarketing spontaneous safety data over 24 years for GSK’s MMR vaccine.MethodsSpontaneous adverse events (AE) reports following vaccination with GSK’s MMR vaccine were collected from GSK’s Global Safety Database from 4-December-1997 until 1-March-2022. Annual reporting trends for pyrexia, rashes (commonly reported in the pediatric population), and events of clinical interest like febrile convulsions and neurological conditions were analyzed from 1998 until 2021. The patient exposure was estimated by the number of doses distributed (DD).ResultsOver the reviewed period, ∼445 million doses of GSK’s MMR vaccine were distributed worldwide, and 29,504 cases were spontaneously reported (rate: 6.63 cases reported/100,000 DD). Of all spontaneous AE reports, 9,960 (33.76%) were considered as serious. For the period analyzed, pyrexia and rash were the most frequently reported AEs following vaccination with GSK’s MMR vaccine (Table). Reports of febrile convulsions had a mean frequency of 0.27 cases/100,000 DD (Table); reports of neurological conditions (encephalitisand/orpanencephalitisand/ormeningitisand/ormeningism) had a mean frequency of 0.07 cases/100,000 DD (Table) and did not show a trend of increased incidence over time.ConclusionThe postmarketing safety data analyzed showed that the safety profile of GSK’s MMR vaccine is consistent with that observed in clinical trials and remains supportive of its overall safety profile in routine use. GSK continues monitoring the safety of its MMR vaccine.FundingGlaxoSmithKline Biologicals SAAcknowledgment:Adina Truta/Julie Mellery provided medical writing/editorial support (Modis c/o GSK)DisclosuresTina Singh, MD physician, GSK: Employee of the GSK group of companies and having restricted GSK shares in the GSK group of companiesGiacomo Casabona, MD, GSK: I’m an employee of the GSK group of companies and shareholder in the GSK group of companiesRemon Abu-Elyazeed, MD, PhD, GSK: Employee of the GSK group of companies and having GSK stocks in the GSK group of companiesVolker Vetter, MD, GSK: I’m an employee of the GSK group of companies and hold shares in the GSK group of companiesFanny Hergibo, Pharm.D., GSK: Employee of the GSK group of companies.