Immune Response to COVID-19 Vaccination in Children With Cancer

Young people undergoing cancer treatment are at increased risk of severe COVID-19 outcomes. Vaccination is recommended; however, data regarding vaccine response are limited.

A prospective cohort study was conducted of children and adolescents (aged 5-19 years) with current solid or hematological cancer and life expectancy of at least 1 year, eligible for COVID-19 vaccination. Participants received 2 or 3 doses of BNT162b2. Blood was taken at baseline, after dose 1, and then 1 and 3 months after subsequent doses. Safety outcomes and patient-reported adverse events were collected. The proportion with neutralizing antibody (NAb) response after 2 vaccine doses was the primary outcome. Vaccine response was measured by NAb titer (positive ≥1:20), T-cell response (interferon-γ, positive ≥10 pg/mL), and binding antibody titer.

Of 113 patients enrolled, 108 (96%) currently or previously received cytotoxic chemotherapy, and most were on current or recent therapy, with 18 (16%) having completed treatment more than 6 months prior to vaccination. Positive NAb response occurred in 52/79 (66%) with samples available after 2 doses and 33/41 (80%) after 3 doses. Interferon-γ response occurred in 44/64 (59%) after 2 doses and 25/34 (74%) after 3 doses. Adverse events were generally mild to moderate, were transient if serious (fever, mucositis, headache), and did not delay cancer treatment. Fever was reported by 12% after doses 1 and 2 and 15% after dose 3.

Most children with cancer respond to BNT162b2 COVID-19 vaccination despite anticancer treatment. Vaccination should not be deferred until treatment completion. These data may have implications for other childhood vaccinations during cancer treatment.