Image of a vial of shingles vaccine labeled "zoster vaccine (recombinant)" on a clinician's work desk.

A study by federal health agencies has identified a small risk of developing Guillain-Barré syndrome (GBS) in Medicare recipients who receive the shingles vaccine Shingrix.

Clinicians should be aware of these risks, but weigh them against the benefits of decreasing the high risk of shingles and its complications in these patients, according to the authors. 

Guillain-Barré syndrome is a neurological disorder that can result in a range of clinical outcomes, from brief weakness to paralysis requiring assistance with breathing. Although rare, it is most frequently seen in adults and the elderly, and has been associated with vaccinations. 

Investigators analyzed medical records documenting GBS cases after vaccination with Shingrix (recombinant zoster vaccine), which is given in two doses two to six months apart. ​​The mean age of participants was 75 years.

They found a risk of three cases per 1 million doses in a 42-day period after full vaccination. 

Shingles is caused by the herpes zoster virus. Almost 1 out of 3 people — usually adults — in the United States will develop the condition in their lifetime, according to the Centers for Disease Control and Prevention. The risk increases with age and the disease can cause debilitating complications. These include postherpetic neuralgia, severe pain that affects up to 18% of patients in the areas where shingles rashes occur. 

Older adults and people who are immunocompromised are more likely to be hospitalized with this and other shingles complications.

Despite the slight risk of Guillain-Barré, the “risk-benefit balance remains in favor of vaccination,” the study’s authors concluded.

The CDC recommends two doses of Shingrix for adults aged 50 years and older, whether or not they have experienced a prior episode of shingles, and whether or not they have been previously vaccinated with a dose of the older drug Zostavax, which is no longer available for use in the United States. 

Full findings were published in JAMA Internal Medicine. Investigators were affiliated with the Centers for Medicare & Medicaid Services, the CDC and the Food and Drug Administration.