Abstract
BACKGROUND/OBJECTIVES: Respiratory Syncytial Virus (RSV) is a common respiratory tract infection that accounts for significant morbidity and mortality, particularly among older adults. From 1 August 2024, the bivalent RSVpreF vaccine (Abrysvo(®)) was introduced in Scotland for eligible older adults. While clinical trials and post-licensure studies showed a good safety profile of the vaccine, post-marketing observational studies in the United States reported a small increased risk of Guillain-Barré Syndrome (GBS) among older adult populations. METHODS: We conducted observed versus expected (OE) and self-controlled case series (SCCS) analyses to retrospectively monitor the incidence of hospital admission for 39 conditions, including GBS. This was undertaken in post-RSV-vaccination periods from 1 August to 31 December 2024, among eligible adults aged 74 to 80 years in Scotland. RESULTS: Observed versus expected analyses identified an increased risk of hospitalisation with GBS in the 1-28-day post-vaccination period. From SCCS analyses, six conditions showed an increased risk in post-vaccination periods (acute coronary syndrome, acute myocardial infarction, acute renal failure, GBS, heart failure and stroke (haemorrhagic)). After temporal adjustment, only GBS remained significant. All 10 hospitalised GBS cases occurred in the 10 to 16 days post-vaccination. Excess risk of GBS was estimated to be 46.1 cases per one million doses. CONCLUSIONS: Study results indicated a good safety profile of the RSV vaccine for older eligible adults aged 75 to 79 years, although a small increased risk of GBS was identified in both analyses. Excess risk levels of GBS from vaccination align with other studies.