Prophylaxis with valganciclovir (VGCV) is used routinely to prevent cytomegalovirus (CMV) infections in at-risk pediatric solid organ transplant (SOT) recipients. However, the rate and factors associated with toxicities in this population are not well-described. We conducted a retrospective cohort study of children undergoing SOT at our hospital from January 2012 - June 2018. We evaluated the frequency of hematologic and renal toxicities from day 15 through 1-year post-SOT in relation to antiviral exposures, focused on VGCV prophylaxis. Marginal rate models were used to determine the risk of kidney injury and neutropenia in relation to VGCV prophylaxis. Among 281 SOTs, VGCV prophylaxis was administered on 20.1% of all follow-up days. The incidence rates of kidney injury, leukopenia, and neutropenia were significantly higher during VGCV prophylaxis compared to when no antiviral agents were given. Using multivariable marginal rate models, receipt of VGCV prophylaxis was associated with development of kidney injury (rate ratio [RR] 1.79, 95% confidence interval [CI]: 1.22-2.65) and neutropenia (RR 4.82, 95% CI: 3.08-7.55). VGCV dosing did not impact the development of kidney injury or neutropenia. Toxicities are common with VGCV prophylaxis in pediatric SOT recipients.

<p><strong>BACKGROUND: </strong>Cytomegalovirus (CMV) is an important cause of morbidity and mortality in pediatric solid organ transplant (SOT) recipients. However, the impact of asymptomatic CMV infections (ie, DNAemia) on clinical outcomes is not well established.</p>

<p><strong>METHODS: </strong>We performed a retrospective cohort study of children undergoing first SOT at our institution from January 2012 to June 2018. We evaluated the epidemiology of CMV infections and performed multivariable Cox regression to assess the association between CMV DNAemia without disease or CMV disease (syndrome or end-organ disease) on negative outcomes (death, re-transplantation, or moderate/severe rejection) within the first year after SOT.</p>

<p><strong>RESULTS: </strong>Among 271 individuals, 43 (15.9%) developed ≥1 CMV infection during the first year after SOT. There were 56 unique CMV infections including 14 episodes of CMV disease. In 167 patients offered CMV prophylaxis, only 8 (4.8%) developed their first CMV DNAemia episode while on prophylaxis 32 developed CMV DNAemia after prophylaxis completion; only 1 episode of CMV disease occurred while on antiviral prophylaxis. When accounting for receipt of ATG, oral steroids, and number of immunosuppressives on a given day, CMV disease was more strongly associated with negative outcomes (Hazard Ratio (HR): 3.28, 95% CI: 0.73-14.64; p&nbsp;=&nbsp;.12) than CMV DNAemia without disease (HR 1.42, 95% CI: 0.19- 10.79; p&nbsp;=&nbsp;.74), although not to a statistically significant degree.</p>

<p><strong>CONCLUSIONS: </strong>Most CMV infections occurred after completion of antiviral prophylaxis. CMV disease was more strongly associated with negative outcomes than asymptomatic CMV DNAemia and should be the focus of CMV prevention practices.</p>

<p><strong>BACKGROUND: </strong>Cytomegalovirus (CMV) is a significant source of morbidity and mortality among transplant recipients; the epidemiology is less understood in pediatric hematopoietic cell transplantation (HCT) cohorts. Furthermore, there is a paucity of data related to CMV prophylactic and preemptive strategies.</p>

<p><strong>METHODS: </strong>A single-center retrospective observational cohort of allogeneic HCT recipients at the Children's Hospital of Philadelphia January 1, 2004-December 31, 2017 was constructed. Subjects were followed for 180 days after transplant to determine whether they had CMV infection or disease. Data on antiviral therapy were collected as were outcomes of CMV disease and adverse events (AEs) related to the antiviral therapy.</p>

<p><strong>RESULTS: </strong>Between January 2004 and March 2017, 345 allogeneic HCTs in 333 patients undergoing CMV surveillance testing were identified. CMV DNAemia was detected during the 180-day follow-up in 89 (25.8%) HCTs. CMV recipient-positive transplants were most likely to have CMV infection (47%). Infection rates were high for those receiving a CMV-specific prophylaxis regimen (50%). CMV DNAemia progressed to CMV disease 11.2% of the time. Of 224 subjects receiving CMV-specific prophylaxis, 19.2% experienced ≥1 AE. Of 53 receiving preemptive therapy during any CMV DNAemia episode, 32.1% experienced ≥1 AE.</p>

<p><strong>CONCLUSIONS: </strong>CMV infection is common in pediatric allogeneic HCT recipients. The CMV-specific prophylaxis regimen employed in this cohort did not effectively prevent DNAemia, progression to CMV disease was uncommon, and AEs from prophylaxis and preemptive therapy were frequent. Novel approaches that reduce the impact of CMV on pediatric allogeneic HCT recipients are needed.</p>

<p>Information about HAdV infection in SOT recipients is limited. We aimed to describe HAdV infection epidemiology and outcomes in a single-center retrospective cohort during the era of PCR availability. SOT recipients transplanted at the CHOP 2004-2013 were followed up for 180&nbsp;days post-transplant. HAdV infection was defined as a positive HAdV PCR from a clinical specimen. HAdV disease was defined by organ-specific radiologic and/or laboratory abnormalities. No HAdV surveillance protocols were employed during the study period; testing was solely per clinician discretion. Progression of HAdV infection was defined as HAdV disease or ≥1-log viral load increase since a corresponding site's first positive specimen. Of the assembled 425 SOT recipients, 227 (52.6%) had ≥1 HAdV PCR. Twenty-four (10.6%) had ≥1 HAdV-positive PCR. HAdV-positive subjects were younger than uninfected subjects (2.0&nbsp;years vs 6.5, P&nbsp;=&nbsp;0.001). Infection incidence rates were highest in liver recipients (15.3%), followed by heart (8.6%), kidney (8.3%), and lung (4.2%). Four subjects (16.7%) met HAdV disease criteria at virus detection. Five subjects (20.8%) had progression of HAdV infection. All-cause mortality rates in positive and negative subjects were 0% and 3.9%, respectively. HAdV infection was infrequently detected in SOT recipients. Over one-third of HAdV-positive patients met disease criteria at detection or had infection progression, but none died. This low all-cause mortality raises questions about benefits of HAdV surveillance. Larger multicenter studies are needed to assess incidence variance by center and comparative effectiveness of therapeutic interventions.</p>