Recombinant Zoster Vaccine May Slightly Increase Risk of Guillain-Barré Syndrome

Immunization with the recombinant zoster vaccine (RZV) may slightly increase the risk of Guillain-Barré Syndrome (GBS) in the Medicare population in the 42 days after administration, according to a study published by JAMA Internal Medicine.

The researchers conducted an observational study of Medicare beneficiaries via a medical record–based, self-controlled analysis of GBS cases following RZV vaccination. They identified a rate ratio of 2.84 between the risk and control windows for an attributable risk of 3 cases per million RZV doses. The study assessed the risk of GBC after administration of RZV, which is administered in 2 doses, 2 to 6 months apart.

The case series cohort study included 849,397 individuals administered RZV and 1,817,099 individuals administered zoster vaccine live (ZVL). All participants were 65 years of age or older.

Self-controlled analyses included events identified from 2,113,758 eligible RZV-vaccinated individuals to compare the relative risk of GBS after RZV compared with ZVL. The researchers followed a claims-based and medical record-based self-controlled case series analyses to assess GBS risk during a postvaccination risk window (days 1-42) compared with a control window (days 43-183).

Those administered the RZV vaccine were observed from October 1, 2017, to February 29, 2020. Patients were identified in the inpatient, outpatient procedural—including emergency department—setting, and office settings using Medicare administrative data. GBS cases were identified through Medicare administrative claims data and cases were assessed via medical record review using the Brighton Collaboration case definition.

Among individuals administered the RZV vaccine, the mean age was 74.8 years at first dose and 58% were women. Among those administered the ZVL vaccine, the mean age was 74.3 years and 60% were women.

In the cohort analysis, the study authors found an increased risk of GBS among those administered the RZV vaccine compared with ZVL vaccinees (rate ratio [RR], 2.34; 95% CI, 1.01-5.41; P = .047). In the self-controlled analyses, the researchers found 24 and 20 cases during the risk and control period, respectively.

The claims-based analysis showed an increased risk in the risk window compared with the control window (RR, 2.84; 95% CI, 1.53-5.27; P = .001), with an attributable risk of 3 per million RZV doses (95% CI, 0.62-5.64), according to the study authors. The medical record–based analysis confirmed the greater risk (RR, 4.96; 95% CI, 1.43-17.27; P = .01).

“Findings of this case series cohort study indicate a slightly increased risk of Guillain-Barré syndrome during the 42 days following RZV vaccination in the Medicare population, with approximately 3 excess Guillain-Barré syndrome cases per million vaccinations,” the study authors wrote. “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.”