Seroprotection after measles vaccination in children with sickle cell anemia receiving hydroxyurea.

Children with sickle cell anemia (SCA) may have decreased antibody responses after some routine vaccines, but it is not known whether this affects the response to measles vaccination. It is critical to determine whether children with SCA develop adequate seroprotection after measles vaccination considering the rise in measles infections in the United States and persistent transmission globally, particularly in regions with high SCA prevalence. It is also unknown whether concurrent hydroxyurea treatment affects the measles antibody response to vaccination. We conducted a retrospective cohort study of children with SCA enrolled in the TREAT trial to determine antimeasles seroprotection (immunoglobulin G of ≥200 IU/L via enzyme-linked immunosorbent assay) after first and second measles vaccine (MV1 and MV2, respectively). Seroprotection was reached by 33 of 35 children (94%) after MV1 and by 46 of 50 (92%) after MV2. Each additional year of age at MV2 was associated with decreased odds of seroprotection (odds ratio [OR], 0.25; P = .02). Hydroxyurea treatment at the time of vaccination did not reduce seroprotection; rather, earlier hydroxyurea initiation was associated with increased seroprotection (OR, 4.4; P = .02). Most children with SCA are adequately protected after measles vaccination, similar to the general population, and seroprotection is increased with timely vaccination and early hydroxyurea treatment. This trial was registered at www.clinicaltrials.gov as NCT02286154.