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Risk of Guillain-Barré syndrome (GBS) increased slightly after receiving the recombinant zoster vaccine (RZV; Shingrix), Medicare claims data showed.

In the 42 days after vaccination, researchers found approximately three excess GBS cases per million vaccinations in the Medicare population, reported Ravi Goud, MD, MPH, of the FDA's Center for Biologics Evaluation and Research in Silver Spring, Maryland, and co-authors.

"Clinicians and patients should be aware of this risk, while considering the benefit of decreasing the risk of herpes zoster and its complications through an efficacious vaccine, as risk-benefit balance remains in favor of vaccination," Goud and colleagues wrote in .

Earlier this year, the FDA issued a adding a warning to the indicating that "in a postmarketing observational study, an increased risk of GBS was observed during the 42 days following vaccination with Shingrix."

"The investigation of Goud and colleagues demonstrates a very modest increased risk of GBS following recombinant zoster vaccination," noted Dennis Bourdette, MD, of Oregon Health and Science University in Portland, who wasn't involved with the study. "However the risk of significant morbidity following shingles easily outweighs the very small risk of GBS."

"Elderly people who develop shingles have at least a one in five risk of post-herpetic neuralgia, which is often severe, prolonged, and disabling," Bourdette told 番茄社区app. "Other potential complications of shingles include secondary skin infections, scarring, vision loss, encephalitis, and myelitis."

"The recombinant zoster vaccine dramatically reduces the risk of developing shingles," he added. "Patients should be cautioned about the small risk of GBS following vaccination but also told about the serious problems associated with developing shingles, which are preventable by the recombinant zoster vaccine."

GBS is an acquired demyelinating polyneuropathy that often begins in the lower extremities and ascends over time with loss of reflexes causing muscle weakness, or in the most severe cases, paralysis. It often is reversible. Some cases may start a few days or weeks after respiratory or gastrointestinal viral infection. In rare cases, vaccinations may increase GBS risk.

Goud and co-authors used Medicare claims data for people 65 and older to evaluate the risk of GBS after zoster vaccine in two analyses:

• In a cohort analysis, they compared 849,397 people vaccinated with RZV and 1,817,099 people who had zoster vaccine live (ZVL; Zostavax) from October 2017 through December 2018
• In a self-controlled case series analysis, they looked at 2,113,758 RZV-vaccinated people 65 and older from October 2017 through February 2020, comparing GBS risk during a post-vaccination window (days 1 to 42) with a control window (days 43 to 183)

GBS was identified in inpatient, outpatient, and emergency department Medicare claims. Cases were assessed through medical record review using the case definition. Of people who received RZV, mean age was 74.8 at first dose and 58% were women, while people receiving ZVL were 74.3 on average and 60% were women.

The cohort analysis showed an increased risk of GBS with RZV compared with ZVL, with a rate ratio (RR) of 2.34 (95% CI 1.01-5.41, P=0.047).

The self-controlled analysis showed 24 cases of GBS during the risk period and 20 cases during the control period (RR 2.84, 95% CI 1.53-5.27, P=0.001), resulting in an attributable risk of 3.13 cases per million doses. A sensitivity analysis using only the set of cases with the highest degree of certainty confirmed an increased risk of GBS after RZV vaccination, with an attributable risk of 5.17 excess cases per million doses in the 42-day risk window.

The study had several limitations, Goud and co-authors acknowledged. The analyses did not adjust explicitly for preceding illnesses and other confounders, but potential influence of preceding illnesses did not appear to diminish results, they said. Some vaccinations may not have been submitted through Medicare. While RZV is approved for individuals ages 50 and older, the study looked only at people 65 and up.

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