TABLE 1.
Summary of methods and characteristics of three 2023/2024 season influenza vaccine effectiveness studies in Great Britain.
| Study characteristics | Study | ||
|---|---|---|---|
| GB–Primary Care (GB‐PC) | England–Hospital (EN‐H) | Scotland–Hospital (SC‐H) | |
| Study period | 4 Sep 2023 to 19 Jan 2024 | 2 Oct 2023 to 15 Jan 2024 | 2 Oct 2023 to 28 Jan 2024 |
| Setting | Primary care | Hospital | Hospital |
| Location | England, Scotland, Wales | England | Scotland |
| Study design | Test negative design | Test negative design | Test negative design |
| Data source | Physicians and laboratory, in some sites data linkage to electronic health records | Data linkage of sentinel laboratory surveillance (Respiratory DataMart), the Immunisations System (IIS), and the Emergency Care DataSet (ECDS) | EAVE‐II national patient‐level dataset, Electronic Communication of Surveillance in SC (ECOSS; all virology testing national database), Rapid Preliminary Inpatient Data (RAPID; Scottish hospital admissions data), National Records of Scotland (NRS; death certification), National Clinical Data Store (NCDS; vaccination events in SC) |
| Age groups of study population | All ages | All ages | All ages |
| Case definition for patient recruitment | Patients consulting within primary care with ARI symptoms | Patients with an influenza swab test 14 days before to 2 days after hospitalisation via emergency care | Patients with EU ARI a symptoms and clinician's judgement that there is an infection b and limited to emergency care where the influenza test occurs 14 days before admission or within 48 hours after admission |
| Selection of patients | At practitioner's/clinician's judgement | At practitioner's/clinician's judgement | At practitioner's/clinician's judgement |
| Vaccine types in the study among controls aged 2–17 | LAIV 96%, QIVc 4% | LAIV 88%, QIVc 12% | LAIV 85%, QIVc 15% |
| Vaccine types in the study among controls aged 18–64 | QIVc 94%, aQIV 4%, QIVe 2%, QIVr 1% | QIVc 86%, aQIV 6%, QIVe 6%, QIVr 3% | QIVc 97%, aQIV 3% |
| Vaccine types in the study among controls aged 65 and above | aQIV 98%, QIVc 2%, QIVr 1% | aQIV 96%, QIVc 3%, QIVr 1% | aQIV 99%, QIVc 1% |
| Vaccination definition | ≥14 days post vaccination | ≥14 days post vaccination | ≥14 days post vaccination |
| Variables of adjustment | Age group, region, clinical risk status, sex, calendar time as week (spline) | Age group, region, clinical risk status, calendar time as week (spline) | Age (spline), sex, number of QCOVID c clinical risk groups (0, 1, 2, 3, 4, ≥ 5) c , time (days, spline), setting (community or hospital) and deprivation quintile (SIMD) |
Abbreviations: aQIV, adjuvanted QIV; ARI, acute respiratory infection; GB, Great Britain; GP, general practitioner; LAIV, quadrivalent live attenuated influenza vaccine; QIVc, cell‐grown quadrivalent influenza vaccine; QIVe, egg‐grown quadrivalent influenza vaccine; QIVr, recombinant quadrivalent influenza vaccine; SIMD, Scottish Index of Multiple Deprivation; TND, test‐negative design.
The EU‐ARI definition is sudden onset of symptoms AND ≥ 1 of cough, sore throat, shortness of breath or coryza AND a clinician's judgement that the illness is due to an infection.
Varies according to SARS‐CoV‐2/influenza testing practices by Health Board.
The QCOVID risk groups are defined as the number of generic comorbidity conditions of a patient, and are used as a measure of comorbidity. The list of conditions is found in the study of Clift et al. [7].