Purpose of review The present review aims to describe in detail the characteristics, outcomes, and recent trends in the field of pediatric intestinal transplantation in the United States. It will examine the route cause and future implications of these developments. The review will draw from recent publications in the field, the Intestinal Transplant Registry, and contemporary data from large U.S. single centers. Recent findings More than 1500 pediatric intestinal transplants have been performed in the United States since 1985, however, over the past decade there have been fewer than 50 transplants/year nationwide. This trend is largely a result of stagnant long-term ITx outcomes and advancements in intestinal rehabilitation programs. Nationally the overall 1-year and 5-year graft survival are 68 and 50% respectively, whereas certain high-volume centers have experienced significantly better results. Sepsis is the leading cause of death following pediatric ITx, whereas rejection is the leading cause of graft loss. Chronic kidney disease and posttransplant lymphoproliferative disorder are significant and relatively prevalent long-term complications. The majority of pediatric ITx recipients receive T-cell depleting induction agents and are on Tacrolimus-based immunosuppression. Most recipient are off parenteral nutrition, but may require supplemental tube feeds. Many pediatric ITx recipients require special education, and in certain domains some report lower health related quality of life. Summary As intestinal rehabilitation has improved in the modern era, the volume of pediatric ITx in the United States has decreased. Although pediatric ITx results have room for improvement nationwide, successful outcomes have been reported at experienced American centers.

Background Information on the safety and immunogenicity of the omicron BA.4/BA.5-containing bivalent booster mRNA-1273.222 are needed. Methods In this ongoing, phase 2/3 trial, 50-μg mRNA-1273.222 (25-μg each ancestral Wuhan-Hu-1 and omicron BA.4/BA.5 spike mRNAs) is compared to 50-μg mRNA-1273, administered as second boosters in adults who previously received a 2-injection (100-μg) primary series and first booster (50-μg) dose of mRNA-1273. The primary objectives were safety and immunogenicity 28 days post-boost. Results Participants received 50-μg of mRNA-1273 (n=376) or mRNA-1273.222 (n=511) as second booster doses. Omicron BA.4/BA.5 and ancestral SARS-CoV-2 D614G neutralizing antibody geometric mean titers (GMTs [95% confidence interval]) after mRNA-1273.222 (2324.6 [1921.2-2812.7] and 7322.4 [6386.2-8395.7]) were significantly higher than mRNA-1273 (488.5 [427.4-558.4] and 5651.4 (5055.7-6317.3) respectively, at day 29 post-boost in participants with no prior SARS-CoV-2-infection. A randomly selected subgroup (N=60) of participants in the mRNA-1273.222 group also exhibited cross-neutralization against the emerging omicron variants BQ.1.1 and XBB.1. No new safety concerns were identified with mRNA-1273.222. Vaccine effectiveness was not assessed in this study; in an exploratory analysis 1.6% of mRNA-1273.222 recipients had Covid-19 post-boost. Conclusion The bivalent omicron BA.4/BA.5-containing vaccine mRNA-1273.222 elicited superior neutralizing antibody responses against BA.4/BA.5 compared to mRNA-1273, with no safety concerns identified.

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