Abstract
BACKGROUND: In pre-vaccinated people with multiple sclerosis (MS), certain disease-modifying therapies (DMTs), particularly the anti-CD20 treatments, appear to be associated with an increased risk of COVID-19 infection and indeed with severe infection. It is still not known if such observations extend to vaccinated individuals and there have been considerably fewer studies in aquaporin-4-antibody neuromyelitis optica spectrum disorder (AQP4-NMOSD) and myelin oligodendrocyte glycoprotein-antibody associated disease (MOGAD) patients. In this study, we investigated the rates of symptomatic COVID-19 infection in adult patients with MS, AQP4-NMOSD and MOGAD who had received 2 doses of SARS-CoV-2 mRNA vaccine. METHODS: This was a prospective observational study conducted at the 2 main neuroimmunology referral centres in Singapore. Only patients on active follow-up were recruited to ensure robust data collection. Data on demographics, disease history, DMTs and SARS-CoV-2 mRNA vaccinations were recorded, and for those infected with COVID-19, data on COVID-19 infection was collected. RESULTS: Nineteen (13 MS, 5 AQP4-NMOSD, 1 MOGAD) out of 365 (231 MS, 106 AQP4-NMOSD, 28 MOGAD) patients had COVID-19 infection despite 2 doses of SARS-CoV-2 mRNA vaccine. Amongst the infected patients, 11 patients were on DMTs (3 rituximab, 2 interferons, 1 azathioprine, 1 mycophenolate, 1 prednisolone, 1 cladribine, 1 alemtuzumab, 1 fingolimod), while 8 patients were untreated. The crude infection rate was calculated using time-at-risk analysis, revealing that rituximab had the highest infection rate amongst all the DMTs. A lower crude infection rate was observed in patients who received a third vaccination. The majority of infections were mild and no patients required oxygen supplementation. CONCLUSION: Our findings suggest that patients on rituximab are still at risk of COVID-19 infection after 2 vaccinations and the receipt of a third vaccination may help to prevent infection. Future large scale studies will be required to better delineate the infection risk of different DMTs after the second and subsequent vaccinations.