1D-01 - Utilization of Near Real-Time, Pre-Adjudicated Claims Data for Timely Insights on the Risk of Guillain-Barré Syndrome (GBS) Following Respiratory Syncytial Virus (RSV) Vaccines during the Early Post-approval Period

Background: Timely safety assessment for newly approved vaccines during their initial uptake period is crucial to inform the benefit-risk profile and assure public confidence. The increasing availability of large real-world data with rapid refreshes and short data lags offers valuable opportunities for early safety assessment. We utilized the monthly-updated Medicare data in an ongoing post-approval safety study for ABRYSVO®.

Objectives: To demonstrate the application of near real-time surveillance for the risk of Guillain-Barré syndrome (GBS) following ABRYSVO vaccination in older adults.

Methods: Medicare fee-for-service claims data were selected based on data recency, size and representativeness. Eligible individuals included adults aged ≥ 65 years who received ABRYSVO from between May 2023 and February 2024 with 12 months of baseline data and no GBS diagnosis before vaccination. GBS cases were identified by a validated algorithm using inpatient claims with GBS as the primary diagnosis. Pre-adjudicated Medicare claims were previously found to have minimal changes ( < 0.5%) in diagnosis codes after adjudication. The risk of GBS was assessed in self-controlled risk interval (SCRI) analyses with a post-vaccination primary risk interval of 1-21 days, a secondary risk interval of 1‑42 days and a control interval of 43-84 days. To account for time-varying confounding and potential misclassification of outcome, the SCRI analysis was adjusted for seasonality and reported positive predictive values of GBS. To achieve >90% data completeness, data cut was allowed to mature for > 3 months before analysis began.

Results: The analytic population included 1,066,945 vaccine recipients across all US regions. Among these, over 90% were white, 52% had a Charlson comorbidity score of ≥ 2 and 41% had concomitant vaccinations with ABRYSVO. Sixteen and 26 GBS cases were observed, respectively, during the primary and secondary risk intervals, yielding a crude incidence rate of 26 and 21 cases per 100,000 person-years, compared to < 11 GBS cases during the control interval (8 per 100,000 person-years). The adjusted SCRI analysis showed an incidence rate ratio of 2.54 (95% confidence interval (CI): 0.87-7.40) for the primary risk interval and 2.05 (95% CI: 0.79-5.33) for the secondary risk interval, compared with the control interval.

Conclusions: Surveillance for 2023-24 season showed a non-statistically significant increased risk of GBS after ABRYSVO vaccination in adults ≥ 65 years of age. Near-real time surveillance methods utilizing large-scale, rapidly refreshed real-world data are an important tool to strengthen the traditional approach for vaccine pharmacovigilance during the early post-approval period.