No link to higher MG risks found with inactivated COVID-19 vaccine

Case series show vaccines did not worsen patients' MG symptoms

Patricia Inacio, PhD avatar

by Patricia Inacio, PhD |

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The use of an inactivated vaccine against SARS-CoV-2, the virus that causes COVID-19, is not linked to an increased risk of symptom worsening among people with myasthenia gravis (MG), according to a small study from China.

“COVID-19 vaccination has no long-term impact on MG relapse,” researchers wrote.

However, a tendency for increased exacerbations, or episodes of sudden symptom worsening, was seen among patients with thymoma-associated MG, with researchers highlighting that “more attention should be paid to thymoma-related MG, especially within 1 week after COVID-19 vaccination.”

The study, “Safety of COVID-19 vaccine in patients with myasthenia gravis: a self-controlled case series study,” was published in the journal Frontiers in Immunology.

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Exacerbations seen with inactivated COVID-19 vaccine were mild

MG is a neuromuscular autoimmune disorder caused by self-reactive antibodies that attack proteins at neuromuscular junctions — the sites of communication between nerve and muscle cells. The rare disorder leads to symptoms of muscle weakness and fatigue.

Infection by SARS-CoV-2 has been linked to the onset of MG. However, whether vaccination against the virus may worsen MG remains controversial. Certain reports favor the link, while others support the vaccine’s safety.

However, because these reports lacked appropriate controls, it remains unknown “whether COVID-19 vaccination increases the risk of symptom exacerbation in MG patients.”

To shed light on this, a team led by researchers at The Fourth Military Medical University, in Xi’an, conducted a retrospective analysis of data from adults with MG, collected from April to October 2022 across two databases.

Participants responded to an electronic questionnaire, which included questions regarding their COVID-19 vaccination status, immunosupressant use, and whether they had experienced exacerbations during the study period — its main goal.

Exacerbations were defined as new onset or worsening of pre-existing muscle weakness reported by the patient or recorded in the database.

Of the 665 electronic questionnaires were sent out, 410 (about 61%) were completed and returned by patients. A COVID-19 vaccine was administered to 108 of the respondents (26.3%), but only 61 were included in the final analysis, as the remaining 47 failed to comply with pre-established criteria. There were 30 women and 31 men included in the analysis. They had a mean age of 45.

A total of 55 patients had received two vaccine doses; six received only one dose. Most patients received an inactivated COVID-19 vaccine — one that relies on the administration of a killed or inactive version of the SARS-CoV-2 virus to trigger an immune response.

Researchers then assessed the number of exacerbations occurring in three different time periods: during the pre-exposure risk period (PEP), which included the 180 days before vaccination; the exposure risk period (ERP), defined as the 28 days following the first shot plus the 28 days after the second shot; and the post-risk period (PRP), which included the period between the first and second vaccination, as well as the period of 29 to 209 days after the second shot.

During the PEP, nine patients experienced 10 disease exacerbations. After vaccination — during ERP — this number decreased to five patients, with a total of six exacerbations registered. The researchers noted that one patient had two exacerbations, both on the day after vaccination. During PRP, 10 disease exacerbations were observed in nine patients.

All exacerbations were mild and no hospitalization was required.

Symptoms resolved within seven days without additional treatment. Only one patient had sustained symptoms, but these resolved within one month following  treatment with low-dose steroids.

Inactivated COVID-19 vaccines do not increase the risk of disease exacerbation in MG patients with stable disease status.

Statistical analysis showed no increased risk of exacerbations in MG patients with stable disease who received one or more doses of an inactivated COVID-19 vaccine.

However, in subgroup analyses, researchers observed that 80% of the patients who had an exacerbation during ERP had a thymoma, or a tumor in the thymus, or had undergone a thymectomy, a surgery to remove the thymus. However, no statistically significant enhanced risk was seen in these cases.

Overall, this small study suggests that “inactivated COVID-19 vaccines do not increase the risk of disease exacerbation in MG patients with stable disease status,” the researchers wrote.