Martínez, Andrés

Background. Measles, mumps, and rubella (MMR) in solid organ transplant (SOT) recipients is rare. We aim to investigate the pretransplant seroprevalence, MMR infection posttransplant, and whether immediate pretransplant MMR vaccination is associated with MMR infection. Methods. We queried the TriNetX database in December 2024 to assess (1) pretransplant MMR seroprevalence, (2) characteristics and outcomes of posttransplant MMR infections, and (3) outcomes for recipients who received the MMR vaccine within 30 d pretransplant. Only US data were included. MMR infection was identified through International Classification of Diseases (ICD) codes. Results. Among 313 548 SOT recipients identified in the database (from 2009 to 2024), IgG positivity for MMR was 72%, 80%, and 78% when available (~5% each). Based on ICD codes, posttransplant MMR infections occurred in 107 (0.03%), 124 (0.04%), and 38 (0.01%) recipients, respectively. The 90-d rejection rates were 36%, 27%, and 42%, whereas mortality rates were 7%, 8%, and 5%, respectively, in patients with MMR infection. Among 114 recipients vaccinated within 30 d pretransplant, none developed posttransplant MMR infections. Conclusions. Overall, posttransplant MMR infections in adult SOT recipients were uncommon in this data set, and no vaccine-associated infections were documented among those who received the MMR vaccine within 30 d pretransplant in real-world practice. The primary limitation of this study is that most MMR infections were identified using ICD codes without confirmation through serological testing or polymerase chain reaction, and we were unable to further characterize the infections because the de-identified database lacked information on the patient’s ZIP code and transplant hospital. Our study highlights the need for improvement in MMR serology screening and pretransplant MMR vaccination.