Burden of Illness in UK Subjects with Reported Respiratory Infections Vaccinated or Unvaccinated against Influenza: A Retrospective Observational Study.
OBJECTIVE
Detailed data are lacking on influenza burden in the United Kingdom (UK). The objective of this study was to estimate the disease burden associated with influenza-like illness (ILI) in the United Kingdom stratified by age, risk and influenza vaccination status.


METHODS
This retrospective, cross-sectional, exploratory, observational study used linked data from the General Practice Research Database and the Hospital Episode Statistics databases to estimate resource use and cost associated with ILI in the UK.


RESULTS
Data were included from 156,193 patients with ≥1 general practitioner visit with ILI. There were 21,518 high-risk patients, of whom 12,514 (58.2%) were vaccinated and 9,004 (41.8%) were not vaccinated, and 134,675 low-risk patients, of whom 17,482 (13.0%) were vaccinated and 117,193 (87.0%) were not vaccinated. High-risk vaccinated patients were older (p<0.001) and had more risk conditions (p<0.001). High-risk (odds ratio [OR] 2.16) or vaccinated (OR 1.19) patients had a higher probability of >1 general practitioner visit compared with low-risk and unvaccinated patients. Patients who were high-risk and vaccinated had a reduced risk of >1 general practitioner visit (OR 0.82; p<0.001). High-risk individuals who were also vaccinated had a lower probability of ILI-related hospitalisation than individuals who were high-risk or vaccinated alone (OR 0.59). In people aged ≥65 years, the mortality rate was lower in vaccinated than unvaccinated individuals (OR 0.75). The cost of ILI-related GP visits and hospital admissions in the UK over the study period in low-risk vaccinated patients was £27,391,142 and £141,932,471, respectively. In low-risk unvaccinated patients the corresponding values were £168,318,709 and £112,534,130, respectively.


CONCLUSIONS
Although vaccination rates in target groups have increased, many people are still not receiving influenza vaccination, and the burden of ILI in the United Kingdom remains substantial. Improving influenza vaccination uptake may have the potential to reduce this burden.
Swansea Center for Health Economics, Swansea University, SA2 8PP, Wales, United Kingdom.
Rhys D
RD
Pockett
College of Biomedical and Life Sciences, Cardiff University, Cardiff, CF14 4YS, Wales, United Kingdom.
John
J
Watkins
Swansea Center for Health Economics, Swansea University, SA2 8PP, Wales, United Kingdom.
Phil
P
McEwan
Health Economics, GSK Vaccines, 1300, Wavre, Belgium.
Genevieve
G
Meier
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D017281:Cost of Illness; D003430:Cross-Sectional Studies; D006760:Hospitalization / Q000191:economics; D006801:Humans; D007251:Influenza, Human / Q000276:immunology*; D008875:Middle Aged; D012141:Respiratory Tract Infections / Q000191:economics*; D012189:Retrospective Studies; D006113:United Kingdom; D014611:Vaccination / Q000191:economics*; D055815:Young Adult