Korean Study Urges Flu Vaccine for MG Patients to Prevent Disease Complications

The risk of aggravating myasthenia gravis (MG) is higher in patients who develop influenza-like illness (ILI) than those who have been vaccinated against influenza vaccination, indicating that people with MG should be immunized, a study finds.

The study, “The Impacts of Influenza Infection and Vaccination on Exacerbation of Myasthenia Gravis,” appeared in the Journal of Clinical Neurology.

Upper respiratory infections (URIs) can exacerbate MG symptoms in some patients, which can lead to a myasthenic crisis. The Centers for Disease Control and Prevention (CDC) recommends the flu vaccine as a preventative step against infection as it can cause potentially serious complications. Yet the vaccine has raised some concerns because it may potentially trigger symptoms of immune-system disorders.

Two prior studies found no link between the vaccine and patient safety in MG patients. However, these studies did not determine the risk for an aggravation of MG symptoms. That led a team of Korean researchers to try to determine whether a risk of both influenza and influenza vaccine exists in patients with MG.

Researchers recruited patients with MG and assessed their history to see if they had experienced a URI the previous winter or had received the vaccine. They also analyzed if MG symptoms had been aggravated either during or post-URI or vaccination.

Researchers evaluated whether patients had ILI, which is differentiated from a common cold by a fever of greater than or equal to 38℃ , and accompanied by a cough or sore throat. To rate the exacerbation of MG symptoms, patients were told to rate their aggravation from 1, which signified “mildest possible exacerbation that did not interfere with daily activities,” to 10, which signified “worst possible exacerbation that required hospitalization.”

Among the 258 recruited MG patients, 133 received flu vaccine and 121 experienced either the common cold (96 patients) or ILI (25 patients). Results showed that MG symptoms were exacerbated in 10 patients (40%) after ILI, while only two patients (1.5%) experienced an exacerbation after the influenza vaccine.  Patients with ILI had a significantly higher rate of exacerbation (40%) than patients with the common cold (15.6%).

The study found a higher risk of MG symptom aggravation after an ILI than after the influenza vaccination, indicating that doctors should offer influenza vaccination to patients with MG as a preventative measure.

“These findings suggest that the influenza infection constitutes a specific and important risk factor for MG symptom exacerbation,” authors concluded. “It is therefore important to apply preventive measures for influenza infection to MG patients, since it is one of only a few modifiable risk factors for exacerbation of that disease.”