Humoral and cellular immunity to SARS-CoV-2 following vaccination with non-mRNA vaccines in adolescent/young adults with cancer: A prospective cohort study

Background Data on SARS-CoV-2 vaccine responsiveness in adolescent/young adult (AYA) cancer patients are sparse. The present study assessed humoral and cellular immune responses post-vaccination in this population. Methods In this prospective study, patients aged 12–30 years undergoing cancer therapy (“on therapy”) and survivors (“off therapy”) were recruited. Anti-receptor binding domain (RBD) protein IgG levels were measured at baseline, four weeks post-first vaccine dose (T1), and six weeks post-second dose (T2). Cellular immunity was assessed using activation-induced markers and intracellular cytokine staining in a patient subset. The primary outcome was to quantify humoral responses in both cohorts at T2 compared to baseline. Clinical predictors of log antibody titres at T2 were identified. Results Between April-December 2022, 118 patients were recruited of median age 15.4 years. Among them, 77 (65.2 %) were in the “on therapy” group, and 77 (65.2 %) had received the BBV152 vaccine. At baseline, 108 (91.5 %) patients were seropositive for anti-RBD antibody. The log anti-RBD titre rose from baseline to T2 (p-value = 0.001) in the whole cohort; this rise was significant from baseline-T1 (p-value < 0.001), but not from T1 to T2 (p-value = 0.842). A similar pattern was seen in the “on therapy” cohort. BECOV-2 vaccine was independently associated with higher log anti-RBD titres than BBV152 (regression coefficient: 0.41; 95 % CI: 0.10–0.73; p = 0.011). Cellular immune responses were similar in the “on-” and “off therapy” groups at the three time points. Conclusion Among AYA cancer patients, a single non-mRNA vaccine dose confers robust hybrid humoral immunity with limited benefit from a second dose.