Does Covid-19 vaccination affect the outcomes of Covid-19 infection in patients with myasthenia gravis? A team of researchers from Canada conducted a population-based, matched cohort study of residents of Ontario to assess the outcomes in this patient group from January 2020 and August 2021.¹ There were 4411 patients with myasthenia gravis out of the 11,365,233 people screened. They were matched on the basis of age, sex and geographic area of residence with 22,055 general population controls and 22,055 controls with rheumatoid arthritis.

Results published online April 25, 2023 in JAMA Network Open show that from January 2020 to May 2021, nearly 4% of patients with myasthenia gravis, 3% of the general population controls and 3% of controls with rheumatoid arthritis developed Covid-19, which was the main study outcome. Covid-related hospitalization, need for intensive care and30-day mortality were also the main outcomes of the study. The rates of ED visits (36.6% vs 24.4% vs 29.9%), hospitalizations (30.5% vs 15.1% vs 20.7%) and mortality at 30 days (14.6% vs 8.5% vs 9.9%) were higher among patients with myasthenia gravis compared with the control group.

About 80.3% of patients with myasthenia gravis had taken two doses of Covid-19 vaccine, the secondary study outcome versus 81.2% of the general population controls. The percentage of participants who had taken one vaccine dose was 3% in myasthenia gravis patients vs 2.8% in the general population controls. Patients who had been vaccinated were less likely to develop Covid-19 compared to the unvaccinated patients with a hazard ratio of 0.43. Less than 6 patients required hospital admission for worsening of their myasthenia gravis within 30 days of taking the first dose of the vaccine.

This study shows that patients with myasthenia gravis who develop Covid-19 are at higher risk of adverse outcomes. The vaccine uptake was high in this patient group; notably, the risk of worsening of disease following vaccination was insignificant. Hence, these patients must be vaccinated on priority with early initiation of treatments for Covid-19 like antivirals or monoclonal antibodies once they develop the infection.

Reference

1. Alcantara M, et al. Outcomes of COVID-19 infection and vaccination among individuals with myasthenia gravis. JAMA Netw Open. 2023 Apr 3;6(4):e239834. doi: 10.1001/jamanetworkopen.2023.9834.