Humoral Immune Response Following COVID-19 Vaccination in Multifocal Motor Neuropathy and Chronic Inflammatory Demyelinating Polyneuropathy.

Background/objectives: Multifocal Motor Neuropathy (MMN) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) are immune-mediated polyneuropathies often treated with immunoglobulin therapy. They were prioritized for COVID-19 vaccination during the pandemic. However, their immune response following COVID-19 vaccination remains unclear. We investigated short- and long-term immune responses to COVID-19 vaccination in patients with MMN and CIDP compared to controls.

Methods: In a prospective observational study, patients with CIDP or MMN and matched controls were followed over 24 months. Controls were age- and sex-matched 1:9. Participants received COVID-19 vaccines in accordance with the Danish vaccination program. Primary outcomes were levels of SARS-CoV-2 IgG antibodies and virus-neutralizing capacity. A positive vaccine response was defined as IgG > 225 AU/mL and neutralizing capacity ≥ 25%.

Results: We included 34 patients and 306 matched controls. While baseline SARS-CoV-2 IgG levels were similar, controls exhibited higher IgG levels at 6- (mean difference, 88%; p = 0.008), 18- (91%; p = 0.023), and 24 months (160%; p < 0.001). Neutralization capacity was also higher in controls at 6 (10%, p = 0.004), 18 (7%, p < 0.001), and 24 months (9%, p = 0.002). Despite this, the proportion of vaccine responders did not differ between the two groups after 24 months (p = 0.196). In patients receiving immunoglobulin therapy, IgG levels were lower than in controls at 24-month follow-up alone (56%, p < 0.001); all demonstrated a positive vaccine response.

Conclusions: Patients with CIDP and MMN demonstrated a positive humoral response to COVID-19 vaccination. Although IgG and neutralization levels were lower than in controls, all patients receiving immunoglobulin therapy were vaccine responders.