Any slightly increased risk of Guillain-Barré syndrome (GBS) after administration of the recombinant zoster vaccine (RZV) is outweighed by the dangers of herpes zoster (HZ) and its complications, according to a new study.
The report in JAMA Internal Medicine focused on RZV, marketed as Shingrix, which is administered in two doses that are 2 to 6 months apart. FDA-led researchers used Medicare claims data to gauge the risk of developing GBS following vaccination with the zoster vaccine.
Included in the case series cohort study were 849,397 participants who had been vaccinated with RZV and 1.8 million who had been vaccinated with zoster vaccine live (ZVL), marketed as Zostavax. All were Medicare beneficiaries aged 65 years or older. Patients receiving RZV vaccines were 58% women, with a mean age of 74.8 years at first dose compared with a mean age of 74.3 years, and 60% women among ZVL recipients.
The researchers evaluated the relative risk of Guillain-Barré syndrome after vaccination with RZV versus ZVL, as well as utilizing claims and medical records to assess risk of the syndrome during a postvaccination risk window (Days 1-42) compared with a control window (Days 43-183).
The study team observed RZV vaccinees using Medicare administrative data from October 1, 2017, to February 29, 2020, identifying inpatients, outpatient procedurals (including emergency departments), and office settings.
"In the cohort analysis we detected an increase in risk of Guillain-Barré syndrome among RZV vaccinees compared with ZVL vaccinees (rate ratio [RR], 2.34; 95% CI, 1.01-5.41; P = .047)," the authors write. "In the self-controlled analyses, we observed 24 and 20 cases during the risk and control period, respectively. Our claims-based analysis identified 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). Our medical record-based analysis confirmed this increased risk (RR, 4.96; 95% CI, 1.43-17.27; P = .01)."
The researchers explain that they identified "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."
They add, however, "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."
Another recent study published in Human Vaccines & Immunotherapeutics bolstered that position. Researchers from the CDC determined that infection with HZ confers a higher risk of GBS.
"The risk of GBS following HZ was increased during the risk window as compared to the primary control window for both groups, with a rate ratio of 6.3 (95% CI, 1.8-21.9) for those 18-64 years and 4.1 (95% CI, 1.9-8.7) for those >65 years," the researchers conclude. "This study provides new and methodologically rigorous epidemiologic support for an association between HZ and GBS, and useful context regarding the benefits versus potential risks of zoster vaccination."
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