Mass COVID-19 vaccination commenced in December 2020 in Scotland. Monitoring vaccine safety relies on accurate background incidence rates (IRs) for health outcomes potentially associated with vaccination. This study aimed to quantify IRs in Scotland of adverse events of special interest (AESI) potentially associated with COVID-19 vaccination. IRs and 95% confidence intervals (CIs) for 36 AESI were calculated retrospectively for the pre-COVID-19 pandemic period (01 January 2015-31 December 2019) and the COVID-19 pandemic period (01 April 2020-30 November 2020), with age-sex stratification, and separately by calendar month and year. Incident cases were determined using International Classification of Diseases-10th Revision (ICD-10)-coded hospitalisations. Prepandemic population-wide IRs ranged from 0.4 (0.3-0.5 CIs) cases per 100,000 person-years (PYRS) for neuromyelitis optica to 478.4 (475.8-481.0 CIs) cases per 100,000 PYRS for acute renal failure. Pandemic population-wide IRs ranged from 0.3 (0.2-0.5 CIs) cases per 100,000 PYRS for Kawasaki disease to 483.4 (473.2-493.7 CIs) cases per 100,000 PYRS for acute coronary syndrome. All AESI IRs varied by age and sex. Ten AESI (acute coronary syndrome, acute myocardial infarction, angina pectoris, heart failure, multiple sclerosis, polyneuropathies and peripheral neuropathies, respiratory failure, rheumatoid arthritis and polyarthritis, seizures and vasculitis) had lower pandemic than prepandemic period IRs overall. Only deep vein thrombosis and pulmonary embolism had a higher pandemic IR. Lower pandemic IRs likely resulted from reduced health-seeking behaviours and healthcare provision. Higher IRs may be associated with SARS-CoV-2 infections. AESI IRs will facilitate future vaccine safety studies in Scotland.

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.

Vaccination continues to be the key public health measure for preventing severe COVID-19 outcomes. Certain groups may be at higher risk of incomplete vaccine schedule, which may leave them vulnerable to COVID-19 hospitalisation and death. To identify the sociodemographic and clinical predictors for not receiving a scheduled COVID-19 vaccine after previously receiving one. We conducted two retrospective cohort studies with ≥3.7 million adults aged ≥18 years in Scotland. Multivariable logistic regression was used to estimate adjusted odds ratios (aOR) of not receiving a second, and separately a third dose between December 2020 and May 2022. Independent variables included sociodemographic and clinical factors. Of 3,826,797 people in the study population who received one dose, 3,732,596 (97.5%) received two doses, and 3,263,153 (86.5%) received all doses available during the study period. The most strongly associated predictors for not receiving the second dose were: being aged 18-29 (reference: 50-59 years; aOR:4.26; 95% confidence interval (CI):4.14-4.37); hospitalisation due to a potential vaccine related adverse event of special interest (AESI) (reference: not having a potential AESI, aOR:3.78; 95%CI: 3.29-4.35); and living in the most deprived quintile (reference: least deprived quintile, aOR:3.24; 95%CI: 3.16-3.32). The most strongly associated predictors for not receiving the third dose were: being 18-29 (reference: 50-59 years aOR:4.44; 95%CI: 4.38-4.49), living in the most deprived quintile (reference: least deprived quintile aOR:2.56; 95%CI: 2.53-2.59), and Black, Caribbean, or African ethnicity (reference: White ethnicity aOR:2.38; 95%CI: 2.30-2.46). Pregnancy, previous vaccination with mRNA-1273, smoking history, individual and household severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positivity, and having an unvaccinated adult in the household were also associated with incomplete vaccine schedule. We observed several risk factors that predict incomplete COVID-19 vaccination schedule. Vaccination programmes must take immediate action to ensure maximum uptake, particularly for populations vulnerable to severe COVID-19 outcomes.