The FDA has updated the prescribing information for Shingrix (Zoster Vaccine Recombinant, Adjuvanted) to include a warning regarding the risk of Guillain-Barré Syndrome (GBS) following vaccination. This decision follows a comprehensive review of postmarketing data, which indicated a potential association between Shingrix and GBS.
Postmarketing Surveillance and Data Analysis
The FDA's evaluation was based on data from a postmarketing observational study and surveillance conducted by the Centers for Disease Control and Prevention (CDC) through the Vaccine Safety Datalink (VSD). These analyses identified a statistical signal suggesting an increased risk of GBS among individuals aged 50 years and older who received Shingrix compared to those who received Zostavax, another shingles vaccine.
To further investigate this signal, the FDA, Centers for Medicare & Medicaid Services (CMS), and CDC collaborated on a study using Medicare claims data. This study, the largest postmarket evaluation of GBS risk following Shingrix vaccination, included 3,729,863 vaccinations administered to 2,113,758 Medicare beneficiaries aged 65 years or older between October 2017 and February 2020.
Risk Assessment and Findings
The risk of GBS following Shingrix vaccination was assessed using self-controlled case series analyses, with a risk window of 1 to 42 days post-vaccination and a control window of 43 to 183 days post-vaccination. The primary analysis revealed an increased risk of GBS during the 42 days following vaccination, with an estimated 3 excess cases of GBS per million doses administered to adults aged 65 years or older. Secondary analyses indicated a higher risk following the first dose of Shingrix, with approximately 6 excess cases per million doses in the same age group, and no increased risk after the second dose. These findings were supported by analyses of GBS cases confirmed through medical record review.
FDA's Conclusion and Recommendations
Despite the observed association, the FDA has stated that the available evidence is insufficient to establish a causal relationship between Shingrix and GBS. However, the agency has determined that including a warning about GBS in the Prescribing Information for Shingrix is warranted. The FDA emphasizes that the benefits of vaccination with Shingrix continue to outweigh its risks.
Hong Kong Regulatory Actions
In Hong Kong, Shingrix is registered as a prescription-only medicine by GlaxoSmithKline Limited. The Department of Health (DH) has not received any adverse drug reaction reports related to Shingrix. Following the FDA's announcement, the DH will inform local healthcare professionals and discuss the matter with the Registration Committee of the Pharmacy and Poisons Board.
