Abstract Details

New onset or exacerbation of MG after vaccination was previously reported.

To investigate whether there is an association between Myasthenia Gravis (MG) and COVID-19 vaccination.

The reporting rate of MG cases after COVID-19 vaccination was compared to that of MG after all other vaccinations in 3 time periods: the vaccine period (December 2020-July 2021); the pre- vaccine pandemic period (April 2020-November 2020) and pre-pandemic period (January 2019-August 2019).  Self-controlled case series analysis and case-centered analysis were used. Six weeks after vaccination was defined as the risk period for possible cause-effect relationship. For self-controlled case analysis, the risk period was followed by one month of washout and another six weeks of control monitoring.

77 and 3 cases with MG after COVID-19 vaccination and all other vaccinations were reported during the vaccine period respectively. The reporting rate of MG after COVID-19 vaccination was significantly higher than the reporting rate of MG after other vaccines (4 vs 0.1 per 10 million p< 0.00001). However, the reporting rate was within the incidence range expected in the general population.  Two cases of MG after vaccination were reported during pandemic period and none in the pre-pandemic period. Using self-controlled and case centered analyses, there is a significant difference in the reporting rate of MG after COVID-19 vaccination between the risk period and control period (92.2% vs 2.6-3.9% p<0.00001). The reporting rate of MG after COVID-19 vaccination was not significantly different between Johnson and Johnson, Moderna and Pfizer vaccines. 

There is no significant increase in reporting rate of MG after COVID-19 vaccination.  Although the reporting rate of MG after COVID-19 vaccination was significantly higher during the risk period compared to the control period, a non-reported or undiagnosed concomitant COVID-19 infection, other triggering factors or non-adherence to medications cannot be excluded; this could account for the observed increase.