<p>Pediatric liver transplant recipients are often transplanted at a young age, precluding them from receiving live virus vaccinations (LVV) such as varicella (VZV) vaccine and measles, mumps and rubella (MMR). This places them at profound risk for vaccine preventable illness. We sought to detail safety of vaccination. This was a retrospective cohort study of pediatric liver transplant recipients at two children's hospitals.&nbsp;Among 204 liver transplant recipients included in the study, 97 received at least one LVV after liver transplant. Six patients who did not receive LVV after transplant had evidence of vaccine-preventable infection following vaccination (1 disseminated VZV disease, 5 VZV-related rash), while one patient who received LVV after transplant developed a diffuse VZV-related rash. Rejection rates were the same between those that did and did not receive a live virus vaccine post-transplant. There were no serious adverse events caused by vaccination post-transplant.&nbsp;Live virus vaccination following liver transplant was safe at our two institutions, although there exist limitations in our study due to its retrospective study design. Larger scale studies should be performed to evaluate the effectiveness of LVV in relation to immunosuppression.</p>

<p><strong>BACKGROUND: </strong>Understanding the prevalence and clinical presentation of COVID-19 in pediatric patients can help healthcare providers and systems prepare and respond to this emerging pandemic.</p>

<p><strong>METHODS: </strong>Retrospective case series of patients tested for SARS-CoV-2 across a pediatric healthcare network, including the clinical features and outcomes of those with positive test results.</p>

<p><strong>RESULTS: </strong>Of 7,256 unique children tested for SARS-CoV-2, 424 (5.8%) tested positive. Patients 18-21 years of age had the highest test positive rate (11.2%) while those 1-5 years of age had the lowest (3.9%). By race, 10.6% (226/2132) of Black children tested positive vs. 3.3% (117/3592) of White children. Of those with an indication for testing, 21.1% (371/1756) of patients with reported exposures or clinical symptoms tested positive vs. 3.8% (53/1410) of those undergoing pre-procedural or pre-admission testing. Of the 424 patients who tested positive for SARS-CoV-2, 182 (42.9%) had no comorbid medical conditions, 87 (20.5%) had asthma, 55 (13.0% had obesity, and 38 (9.0%) had mental health disorders. Overall, 52.1% had cough, 51.2% fever, and 14.6% shortness of breath. Seventy-seven (18.2%) SARS-CoV-2 positive patients were hospitalized, of which 24 (31.2%) required any respiratory support. SARS-CoV-2-targeted antiviral therapy was given to 9 patients, and immunomodulatory therapy to 18 patients. Twelve (2.8%) SARS-CoV-2 positive patients developed critical illness requiring mechanical ventilation and 2 patients required extracorporeal membrane oxygenation. Two patients died.</p>

<p><strong>CONCLUSIONS: </strong>In this large cohort of pediatric patients tested for SARS-CoV-2, the rate of infection was low, but varied by testing indication. The majority of cases were mild, few children had critical illness, and two patients died.</p>