Humoral response and safety of BNT162b2 mRNA vaccine in children with rheumatic diseases

The coronavirus disease 2019 (COVID-19) vaccine represents a cornerstone in tackling the pandemic and with the approval of the BNT162b2 mRNA vaccine in December 2020, it has become a beacon of hope for people around the world, including children. This study aimed to present the data on the humoral response and safety of vaccine in a cohort of patients with paediatric rheumatic diseases receiving immunomodulatory treatments. Forty-one children with paediatric rheumatic diseases were included and were vaccinated with the BNT162b2 mRNA vaccine (two doses of 30 µg administered 3-4 weeks apart). To assess the humoral response, IgG antibodies developed against the S1/Receptor-binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein at baseline and 3-4 weeks after the second dose were measured. The possible local and systemic side effects and disease activity scores were evaluated during the study period. After the second dose of vaccine, markedly elevated anti-RBD IgG titres were observed in all patients with a median titre of 20 474 AU/ml [interquartile range (IQR) 6534-36 151] with a good safety profile. The median disease duration was 4.3 (IQR 3.5-5.6) years. In the cohort, 14 (34.1%) received conventional DMARDs (cDMARDs), 16 (39%) received biologic DMARDs (bDMARDs) and 11 (26.8%) received a combined therapy (cDMARDs and bDMARDs). Patients treated with combined therapy [median 4695 (IQR 2764-26 491)] had significantly lower median titres of anti-RBD IgG than those receiving only cDMARDs. Paediatric rheumatic diseases patients receiving immunomodulatory treatments were able to mount an effective humoral response after two dose regimens of BNT162b2 mRNA vaccine safely without interrupting their current treatments.