Serological Benefit of SARS-CoV-2 Vaccination Relative to Infection in Children With Acute Lymphoblastic Leukemia

Children with acute lymphoblastic leukemia (ALL) are at risk of severe outcomes from SARS-CoV-2 (SCV2). In the post-pandemic context, where most children have been infected with SCV2, there are limited data on whether vaccination remains beneficial in children with ALL.

We recruited children with ALL, mostly in the maintenance phase of chemotherapy, and healthy controls who were infected and/or vaccinated with SCV2. Antibody concentrations and avidity against the SCV2 spike (S) protein and its receptor-binding domain (RBD) were measured, as were the frequencies of S-specific cytokine-positive T cells and the concentrations of secreted cytokines.

Antibody levels and avidity were lower in children with ALL than in healthy controls, regardless of when exposure occurred relative to ALL diagnosis. Among children with ALL, vaccination generated greater anti-RBD antibody levels than infection. Three or more vaccine doses were associated with more robust and higher avidity responses, similar to those of the healthy controls. Antibody levels were more durable in vaccinated children with ALL compared to unvaccinated children. T-cell responses were similar in healthy controls and children with ALL, although children with ALL showed decreases in the secretion of some cytokines. Among children with ALL, T-cell responses did not differ by vaccination status and were stable over time.

We identified a significant serological benefit of SCV2 vaccination relative to infection, in terms of antibody avidity, level, and durability. These data can support clinicians in making evidence-based vaccine recommendations for children with ALL.