Posaconazole (MK-5592) Intravenous and Oral in Children With Invasive Aspergillosis (IA) (MK-5592-104)

Inclusion Criteria: * Has a diagnosis of possible, probable, or proven IA per modified 2008/2020 European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) disease definitions * Has one or more of pre-defined risks as per modified 2008 EORTC/MSG disease definitions * Has a central line (e.g., central venous catheter, peripherally-inserted central catheter) in place or planned to be in place prior to beginning IV study treatment. * Has clinical symptoms consistent with an acute episode of IA, defined as duration of clinical syndrome of \<30 days. * Participants weigh at least 10 kg, and may be of any race/ethnicity. * During the intervention period and for at least 30 days after the last dose of study treatment, males agree to be abstinent from heterosexual intercourse or use contraception unless confirmed to be azoospermic (vasectomized or secondary to medical cause). * Female is not pregnant or breastfeeding, and is not a woman of child bearing potential (WOCBP) or is a WOCBP using a highly effective contraceptive method. A WOCBP must have a negative highly sensitive pregnancy test (urine or serum as required by local regulations) within 24 hours before the first dose of study intervention. Exclusion Criteria: * Has chronic (≥30 days' duration) IA, relapsed/recurrent IA, or refractory IA that has not responded to prior antifungal treatment. * Has cystic fibrosis, pulmonary sarcoidosis, aspergilloma, or allergic bronchopulmonary aspergillosi…