Favourable humoral but reduced cellular immune response to COVID-19 mRNA BNT162b2 vaccine in patients with childhood-onset systemic lupus erythematosus.

Objective: To evaluate both humoral and cellular immune responses to the COVID-19 messenger RNA (mRNA; BNT162b2) vaccine in patients with childhood-onset SLE (cSLE) compared with healthy controls and patient controls (kidney transplant (KTx) recipients).

Methods: This single-centre, cross-sectional and case-control study included 16 patients with cSLE, 19 healthy controls and 19 KTx recipients. We assessed SARS-CoV-2-specific humoral (anti-SARS-CoV-2 IgG, neutralising antibody (nAb)) and cellular (interferon gamma release assay (IGRA)) immune responses at least 1 month after administration of two doses of the mRNA vaccine.

Results: Humoral immune response rates (anti-SARS-CoV-2 IgG and nAb seropositivity) in patients with cSLE were comparable to healthy controls (100% vs 100% and 100% vs 95%, respectively) but significantly higher than in KTx recipients (74% and 42%, p<0.05 for both). Cellular immune response rate measured by IGRA was lower in patients with cSLE compared with healthy controls (56.3% vs 89.5%, p=0.050) and comparable to KTx recipients (63%). IGRA-negative patients with cSLE had significantly lower total leucocyte and lymphocyte counts at vaccination time as compared with their counterparts (p=0.008 and p=0.001, respectively). No differences were found in disease activity or immunosuppressive therapies between IGRA-negative and IGRA-positive patients with cSLE.

Conclusion: Patients with cSLE showed robust humoral but compromised cellular immune responses to the COVID-19 mRNA vaccine, associated with lower lymphocyte counts. These findings highlight the need for further research to enhance vaccine efficacy in this vulnerable group.