In October following vaccination, participants may have a pre-RSV season blood collection visit. During RSV season, November through March following vaccination, researchers will contact participants' parents or guardians on a weekly basis for follow-up monitoring. During this time frame, participants seen by a medical provider for fever, respiratory illness, or otitis media will have a study visit, which will include a nasal wash and clinical assessment. In April following vaccination, participants will undergo a final blood collection.