Risk of COVID-19 in people with multiple sclerosis who are seronegative following vaccination.

BACKGROUND: People with multiple sclerosis (pwMS) treated with certain disease-modifying therapies (DMTs) have attenuated IgG response following COVID-19 vaccination; however, the clinical consequences remain unclear. OBJECTIVE: To report COVID-19 rates in pwMS according to vaccine serology. METHODS: PwMS with available (1) serology 2-12 weeks following COVID-19 vaccine 2 and/or vaccine 3 and (2) clinical data on COVID-19 infection/hospitalisation were included. Logistic regression was performed to examine whether seroconversion following vaccination predicted risk of subsequent COVID-19 infection after adjusting for potential confounders. Rates of severe COVID-19 (requiring hospitalisation) were also calculated. RESULTS: A total of 647 pwMS were included (mean age 48 years, 500 (77%) female, median Expanded Disability Status Scale (EDSS) 3.5% and 524 (81%) exposed to DMT at the time of vaccine 1). Overall, 472 out of 588 (73%) were seropositive after vaccines 1 and 2 and 222 out of 305 (73%) after vaccine 3. Seronegative status after vaccine 2 was associated with significantly higher odds of subsequent COVID-19 infection (odds ratio (OR): 2.35, 95% confidence interval (CI): 1.34-4.12, p = 0.0029), whereas seronegative status after vaccine 3 was not (OR: 1.05, 95% CI: 0.57-1.91). Five people (0.8%) experienced severe COVID-19, all of whom were seronegative after most recent vaccination. CONCLUSION: Attenuated humoral response to initial COVID-19 vaccination predicts increased risk of COVID-19 in pwMS, but overall low rates of severe COVID-19 were seen.

Incidence of persistent lymphopenia in people with multiple sclerosis on dimethyl fumarate.

BACKGROUND: Dimethyl fumarate (DMF) is a disease modifying therapy (DMT) used in the management of Multiple Sclerosis (MS). Lymphopenia occurs in approximately 30% of people receiving this medication. The recently revised Summary of Product Characteristics (SPC) recommends increased monitoring or cessation of this medication in the context of persistent lymphopenia, because of an increased risk of progressive multifocal leukoencephalopathy (PML). It is therefore important for clinicians and patients to be aware of the frequency of persistent, moderate-severe lymphopenia in order to make informed decisions regarding drug choice and safety monitoring. METHODS: We reviewed medical records of 156 people with MS (PwMS) started on DMF between 2014 and 2020, who received at least 6 months of treatment, in order to identify the incidence and duration of persistent lymphopenia. RESULT: Ten were excluded due to missing data. In 146 patients, treated for 30.7 months (mean), 16 (11%) were found to experience persistent moderate lymphopenia (0.5-0.7 × 109/L) and 5 (3%) experienced persistent severe lymphopenia (<0.5 × 109/L). Of the 5 patients with persistent severe lymphopenia, 3 discontinued DMF. Two cases stopped directly due to SPC recommendations and after 6-months no further DMTs were initiated. Treatment was withdrawn in a further case due to lack of efficacy. Two cases remained on DMF as their persistent severe lymphopenia predated SPC revision. Mean times to persistent moderate and severe lymphopenia were 10.6 months and 25.5 months respectively. Increased age was a predictor for persistent lymphopenia (B = 0.071, p = 0.004) while sex, and previous DMT were not.