A case of myositis of the deltoid muscle of the upper arm developing 1 week after influenza vaccination: case report

A Rare Case of Toxic Myositis Associated with Influenza Vaccination

The influenza vaccine is one of the most commonly administered vaccines worldwide, with a high safety profile. However, rare cases of serious adverse events have been reported in the literature. We report a 77-year-old male who presented with progressive weakness in the lower extremities shortly after receiving the Influenza vaccine. He was diagnosed with myositis involving the paraspinal and bilateral lower extremity muscles. He received treatment with high-dose steroids and taper with full recovery of his muscle weakness. Although the exact causal mechanism between the vaccine and the patient's myositis could not be established, surveillance for such rare adverse events can provide data for future vaccine safety improvement. Due to well-known benefits of the Influenza vaccine that far exceed the potential adverse effects, we strongly encourage the readers to continue their vaccine practices as per CDC guidelines.

Isolated Infraspinatus Myositis after Intramuscular Vaccine Administration

Case

A 74-year-old female developed left shoulder pain after receiving an influenza vaccine. Her initial physical exam was suggestive of subacromial bursitis, and a corticosteroid injection into the subacromial space resulted in a 50% improvement in her pain. Subsequent MRI demonstrated myositis isolated to the infraspinatus muscle. She was successfully treated with anti-inflammatory medication and physical therapy.

Conclusion

Shoulder injury related to vaccine administration (SIRVA) is a rare clinical complication, and myositis in the rotator cuff musculature has not been previously reported. Proper administration of intramuscular vaccinations should be emphasized to prevent injury to structures surrounding the shoulder joint.

Influenza Vaccination and Guillain-Barré Syndrome: Reality or Fear

Guillain-Barré syndrome (GBS) is an inflammatory disorder and an acute immune-mediated demyelinating neuropathy that causes reduced signal transmissions, progressive muscle weakness, and paralysis. The etiology of the syndrome still remains controversial and uncertain. GBS can be initiated and triggered by respiratory tract infections such as influenza, and intestinal infections such as Campylobacter jejuni. In addition, there is considerable evidence suggesting links between influenza vaccination and GBS. As reported previously, the incidence of GBS in individuals receiving swine flu vaccine was about one to two cases per million. Despite the influenza vaccine efficacy, its association with an immune-mediated demyelinating process can be challenging as millions of people get vaccinated every year. In this review we will discuss the association between influenza infection and vaccination with GBS by focusing on the possible immunopathological mechanisms.