Investigate risk factors for short term reactivation of retinopathy of prematurity (ROP) after intravitreal ranibizumab (IVR) therapy and determine safety and efficacy of repeat injections.Retrospective chart review study of patients screened for ROP as inpatients between 2013-2023 who received IVR within the UCLA healthcare system. Primary outcomes were rates and timing of short term ROP reactivation, defined as repeat worsening of ROP to stage 2 or 3 before 52 weeks postmenstrual age (PMA), as well as risk factors for reactivation. Other outcomes included adverse events and rates of reactivation after a second intravitreal injection.82 eyes of 43 patients received primary IVR 0.25mg/0.025cc for type 1 ROP. 13 patients (22 eyes) (30.2% of patients, 26.8% of eyes) developed short term reactivation an average of 7.2±1.7 weeks after treatment. Increased reactivation risk was associated with zone I disease (OR 6.23, 95% CI 1.35-28.7, p=0.019), lower PMA at 1st injection (OR 1.64, 95% CI 1.19-2.26; p=0.003), and lower gestational age at birth (OR 1.80, 95% CI 1.04-3.13, p=0.037). Of the 13 patients that received repeat injections, 5 required laser treatment for a second reactivation (11.6% of patients receiving IVR). No eyes developed retinal vascular occlusion, endophthalmitis or cataract.Repeat injections may be required after primary IVR for aggressive ROP. Repeat IVR treatment for ROP is effective and poses few ophthalmic adverse events, though additional reactivation remains a risk.