Negligible Risk of Myasthenia Gravis Exacerbations After COVID-19 Vaccination

Monica Alcantara, MD, PhD

Credit: American Neuromuscular Foundation

Adults with myasthenia gravis who contracted COVID-19 show a higher risk of hospitalization and death compared with matched controls, a new study reports. Vaccine uptake was high, with negligible risk of severe myasthenia gravis exacerbations after vaccination, as well as evidence of effectiveness.¹

The COVID-19 pandemic has affected millions of people worldwide, and the scientific community has been working hard to understand how different populations are affected by the virus. People with underlying medical conditions, such as myasthenia gravis, may be at increased risk of severe COVID-19 outcomes.²

Myasthenia gravis is a rare neuromuscular disorder that affects voluntary muscles used for breathing, swallowing, and speaking. Limited data are available on COVID-19 outcomes and vaccine safety among this population. The objective of this study was to investigate COVID-19-related outcomes and vaccine uptake among a population-based sample of adults with myasthenia gravis in Ontario, Canada.¹

Examining COVID-19 and Myasthenia Gravis

Monica Alcantara, MD, PhD, of Ellen & Martin Prosserman Centre for Neuromuscular Diseases, Toronto General Hospital, University Health Network, University of Toronto, and a team of investigators conducted the population-based, matched cohort study with administrative health data from January 2020 - August 2021.

Adults with myasthenia gravis were identified using a validated algorithm, and each patient was matched by age, sex, and geographic area of residence to 5 controls from the general population and a cohort of individuals with rheumatoid arthritis (RA).

The main outcomes were COVID-19 infection and related hospitalizations, intensive care unit (ICU) admissions, and 30-day mortality among patients with myasthenia gravis compared with controls.

The secondary outcome was the uptake of COVID-19 vaccination among patients with myasthenia gravis compared with controls.

Higher Risk Reduced with COVID-19 Vaccination

Among 11,365,233 eligible Ontario residents, 4411 patients with myasthenia gravis (mean [SD] age, 67.7 [15.6] years; 2274 women [51.6%]) were matched to 22,055 general population controls (mean [SD] age, 67.7 [15.6] years; 11,370 women [51.6%]) and 22,055 controls with RA (mean [SD] age, 67.7 [15.6] years; 11,370 women [51.6%]).

Between January 2020 - May 2021, 164 patients with myasthenia gravis (3.7%), 669 general population controls (3.0%), and 668 controls with RA (3.0%) experienced COVID-19 infection.

Patients with myasthenia gravis exhibited higher rates of COVID-19-associated emergency department (ED) visits, hospital admissions, and 30-day mortality when compared with controls.

Investigators found by August 2021, 3540 patients with myasthenia gravis (80.3%) had received 2 COVID-19 vaccine doses, compared with 17,913 individuals of the general population control (81.2%).

Respectively, 137 (3.1%) and 628 (2.8%) had received 1 dose. Fewer than 6 individuals were hospitalized for myasthenia gravis worsening within 30 days of vaccination. Investigators observed a lower risk of contracting COVID-19 in those with myasthenia gravis who were vaccinated compared with unvaccinated patients with the rare condition.

The findings suggest adults with myasthenia gravis who experienced COVID-19 infection had a higher risk of hospitalization and death compared with controls. The vaccination acceptance rate was substantial, and the possibility of severe myasthenia gravis-related exacerbations following vaccination was insignificant, along with evidence of its efficacy.

Investigators emphasized the need for public health policies promoting vaccination for this population in addition to new COVID-19 therapeutics. It is important to continue monitoring the safety and efficacy of COVID-19 vaccines among individuals with myasthenia gravis and other underlying medical conditions, they wrote.

References:

1. Alcantara M, Koh M, Park AL, Bril V, Barnett C. Outcomes of COVID-19 Infection and Vaccination Among Individuals With Myasthenia Gravis. JAMA Netw Open. 2023;6(4):e239834. doi:10.1001/jamanetworkopen.2023.9834
2. Kassardjian  CD, Widdifield  J, Paterson  JM,  et al. Serious infections in patients with myasthenia gravis: population-based cohort study. Eur J Neurol. 2020;27(4):702-708. doi:10.1111/ene.14153