The Societal and Indirect Economic Burden of Seasonal Influenza in the United Kingdom

Introduction and Objectives

Seasonal influenza is a significant public-health issue. In the United Kingdom (UK), the influenza season runs from approximately October to March and is associated with an increased demand for and pressure on the nation's healthcare system (the National Health Service [NHS]). Seasonal influenza's direct health and economic impacts (i.e. costs related to healthcare utilisation) have received considerable attention in the literature. However, less attention has focused on its broader societal burden, i.e. its socioeconomic impact on individuals and populations in which these individuals reside. The societal burden of seasonal influenza may include productivity loss in the national workforce due to sick days and an increased burden on the NHS, with ripple effects on the provision of routine services.

This study examined the societal burden of seasonal influenza, particularly its impact on workforce productivity and the provision of NHS services in the UK, which are under-explored. We also sought to quantify seasonal influenza's indirect economic costs (i.e. non-medical costs) due to labour-productivity losses.

Approach

To address this study's objectives, we undertook the following:

• A literature review: We conducted a rapid evidence assessment (REA) of the literature to understand the societal burden of seasonal influenza in the UK. The REA focused on seasonal influenza's downstream societal impacts, especially workplace absenteeism and presenteeism.
• A secondary database analysis: We analysed publicly available aggregated data from NHS England and NHS Digital between August 2010 and June 2022 to better understand seasonal influenza's impact on NHS service provision before and after the 2019 coronavirus disease (COVID-19) pandemic. We focused on specific longitudinal metrics related to the primary and secondary care settings we believe the influenza season might have affected.
• A public survey: We conducted a geographically representative survey of 1,000 working-age adults (aged 18–64) across the UK who reported having influenza or caring for a dependent with influenza during at least one of the past four influenza seasons (from Autumn 2018 to Spring 2022). The survey was designed to understand the impact of seasonal influenza on workplace absenteeism and presenteeism, lost wages and out-of-pocket costs.
• NHS stakeholder interviews: We conducted interviews with 20 key NHS stakeholders from primary care (general practitioners [GPs]) and secondary care (Accident & Emergency [A&E], general surgery and oncology) across the four UK nations (England, Wales, Scotland and Northern Ireland). Departments were selected based on NHS services where we expected the most significant potential impacts from seasonal influenza. Interviews focused on the impact of seasonal influenza on NHS service provision before and during the COVID-19 pandemic.
• Epidemiologic-economic modelling: We used an epidemiologic Susceptible-Infected-Recovered (SIR) model to estimate the prevalence of seasonal influenza cases, calibrated to a “post-COVID” world where seasonal influenza cases rise but do not reach pre-pandemic levels. We based this epidemiologic model on previously published estimates of influenza infection and recovery rates, influenza prevalence estimates and the efficacy of annual influenza vaccines. The model also used rates of influenza vaccination from the public survey. Next, we used a macroeconomic computable general equilibrium (CGE) model to estimate the indirect economic costs associated with lost economic productivity. This model used a predicted influenza prevalence based on the epidemiologic model to estimate influenza case numbers and associated productivity losses from the public survey.

Key Research Findings

We present our research findings thematically. First, we describe findings regarding seasonal influenza's impact on the working-age UK population. Second, we describe findings on seasonal influenza's impact on the NHS, and finally, we describe findings on its indirect economic impact.

The Impacts of Seasonal Influenza on Working-Age UK Adults

Absenteeism

• Working adults in the UK may require time away from work due to having influenza or caring for a dependent with influenza, with approximately two to four working days lost, on average, per person [literature review; public survey].
• UK National Insurance benefits help mitigate against lost wages due to employees' influenza-related absences from work but may only partially replace lost wages [literature review].
• Influenza-related absences can impact small and medium-sized enterprises (SMEs) via lost productivity [literature review].

Presenteeism and Productivity Loss

• More than half of UK working adults report working for at least some of the time they have influenza or are caring for a dependent with influenza, and are 35–46% less productive at work during this time on average [public survey].
• Being at work while ill can put co-workers at risk and has multiple drivers, including work culture (norms, expectations and trust levels) and wage arrangements [literature review].

Personal Financial Costs

• Approximately 40–60% of working-age UK adults with influenza or caring for a dependent with influenza report out-of-pocket costs or lost wages due to absenteeism [public survey].

Vaccinations' Impact on the Societal Burden of Seasonal Influenza

• Influenza vaccine uptake in the general UK population is low. However, it is higher among older vs younger working-aged adults and in healthcare workers vs those in other sectors [literature review; public survey].
• Some evidence suggests that vaccinating older working-age UK adults can reduce absenteeism-related costs [literature review].
• Some evidence suggests that influenza is associated with a reduced quality of life in the UK. However, this could potentially be mitigated among older working-age adults via increased vaccine uptake [literature review].

The Impacts of Seasonal Influenza on the NHS

General Impacts on the NHS

• In general, NHS stakeholders perceive the influenza season to have a moderate-to-severe impact on routine healthcare services that can worsen with more virulent strains, including the COVID-19 pandemic [interviews].

The Impact of NHS Staff Absences

• Compared to other months, the influenza season is associated with NHS staff absences both before and during the COVID-19 pandemic, averaging more than 5,000 excess full-time-equivalent (FTE) staff absent per month [secondary analyses].
• Healthcare-worker absenteeism rates vary during a typical UK influenza season. However, they are generally higher in more virulent seasons and during the COVID-19 pandemic, with some NHS stakeholders recording 15–20% of staff absent for approximately one week [interviews].
• The presenteeism culture among healthcare workers in the UK may lower absenteeism rates during the influenza season. However, it may also put co-workers, patients and the broader community at risk of infection [interviews].

The Impact on Healthcare Workers' Psychological Well-Being

• Healthcare workers can experience a higher psychological burden during the influenza season due to staff absences and increased patient volumes [literature review], potentially increasing absenteeism.

Impacts on Primary-Care Services

• Healthcare-worker absences are the most commonly reported disruptions to NHS primary-care services during the influenza season [interviews].
• However, rescheduling or cancelling appointments in NHS primary-care settings during the influenza season is not perceived as a major issue because GP practices often plan for potential disruptions, e.g. reduced workforce capacity [interviews].
• Waiting times for routine appointments in NHS primary-care settings vary substantially but are not perceived to be significantly impacted by the influenza season [interviews].

Impacts on Secondary-Care Services

• Waiting times to see clinicians in A&E are longer during the influenza season than at other times [interviews; secondary analyses].
• Higher volumes of hospitalised patients during the influenza season cause A&E backlogs [interviews; secondary analyses].
• Compared to other months, the influenza season is associated with:
  • Increased emergency inpatient admissions from A&E, averaging more than 27,000 excess admissions per month [secondary analyses].
  • More patients waiting longer to be admitted to hospital from A&E, averaging nearly 16,000 extra patients per month waiting more than four hours [secondary analyses].
  • Increased cancellations of elective procedures, averaging nearly 3,000 excess procedures cancelled per quarter [secondary analyses].
  • Increased use of inpatient critical-care beds (although negligible in absolute terms) [secondary analyses].

Impacts on Outpatient Treatment and Diagnostic Tests

• Compared to other months, the influenza season is not associated with longer waiting times for NHS outpatient treatments or diagnostic tests [secondary analyses].

Impacts of Vaccine Uptake Among Healthcare Workers

• Influenza-vaccine uptake among NHS healthcare workers varies [literature review; interviews; public survey].
• Some evidence suggests that cost savings associated with vaccinating NHS healthcare workers against influenza mitigates the impact of absenteeism [literature review].

The Indirect Economic Impacts of Seasonal Influenza

Seasonal Influenza and Lost Working Days

• An estimated 2.4 million working adults could contract influenza annually in the UK, corresponding to 4.8 million lost working days [epidemiologic model].
• Increasing current worker vaccination rates by just ten percentage points per sector could reduce infections by approximately 40% (n = 1 million), translating into 1.9 million fewer lost working days [epidemiologic modelling].

Seasonal Influenza's Effects on the UK's Economy

• Seasonal influenza is associated with a £644m loss to the UK's economy (0.04% of GDP), equivalent to approximately £272 per infected worker [economic modelling].
• Increasing workers' vaccination rates by ten percentage points per sector could increase the UK's economic output by £258m per year (or £83 per additional vaccination) [economic modelling].
• Each ten-percentage-point increase in workers' vaccination rates (ranging from 0–60% vaccinated) is associated with an average gain of £380m to the UK economy [economic modelling].

Considerations

Based on these findings, we offer several recommendations for future research, policy and practice.

Stakeholders should consider policies that better protect workers against wage losses due to influenza-related absence.

Our research shows that UK workers commonly lose wages due to seasonal influenza. Since current policies do not fully protect workers, they may continue working while ill to avoid losing wages. This disadvantage disproportionately impacts self-employed or hourly/daily-wage earners with no or inadequate contractual sick leave. Such policies could help avoid presenteeism and its downstream effects.

Workplaces could benefit from fostering cultures discouraging presenteeism.

Employees attending workplaces while ill with influenza or caring for a dependent with influenza are (a) less productive and (b) putting co-workers and the public at risk. Employers could work with their Human Resources departments to develop more facilitative sick-leave policies that encourage employees to take time off when they or a family member are ill. This consideration is particularly important for public-facing roles, including those interacting with at-risk populations (e.g. health and social care workers).

Wider vaccine uptake could reduce avoidable healthcare visits during the influenza season and increase the UK's economic output.

The NHS provides free influenza vaccinations to at-risk populations to encourage uptake. Beneficiaries include school-aged children, those with comorbid conditions, healthcare workers and adults aged 65+ (lowered to 50+ during the COVID-19 pandemic). Nevertheless, vaccine uptake in these high-risk populations remains suboptimal. Therefore, strategies encouraging influenza-vaccine uptake in these groups are needed to help reduce avoidable healthcare visits and alleviate pressure on the NHS during the influenza season. The NHS has not encouraged influenza-vaccine uptake in lower-risk working adults because such vaccination programmes do not appear to be cost-effective. However, our research shows that seasonal influenza is associated with approximately 4.8 million lost working days in the UK, resulting in a £644m annual loss to the UK economy. Future research is needed to understand whether more widespread vaccination programmes could offset these GDP losses.

Research is needed to understand how the NHS can alleviate increasing pressures on service provision exacerbated by seasonal influenza and COVID-19 and prepare for future public health threats.

Routine NHS services have been under increasing pressure for at least a decade, with longer waits for appointments, procedures and treatments across departments. The influenza season exacerbates this pressure via the deluge of acute-respiratory illnesses presenting to GP surgeries and A&E departments, some requiring inpatient care. The COVID-19 pandemic's onset has only worsened matters, and new public health threats may be on the horizon. Research should focus on where greater healthcare-system efficiencies are needed to allocate additional NHS investment in an evidence-based manner. Such research should consult NHS workers and patients, who are most aware of the issues.

The UK could benefit from more robust infectious-disease surveillance systems.

Current estimates of seasonal influenza's impact derive from healthcare system records, with limited population-wide laboratory-confirmation. Through the COVID-19 Genomics UK Consortium (COG-UK Consortium, 2023), the COVID-19 pandemic has provided valuable lessons in the surveillance of severe acute respiratory coronavirus 2 (SARS-CoV2) applicable to other infectious diseases. This is particularly important as SARS-CoV2 will likely become endemic, coinciding with influenza and other respiratory illnesses during the winter; however, we know very little about COVID-19/influenza co-infection and its potential impacts. Furthermore, more robust surveillance systems can promote early detection of emerging infectious disease threats, enabling better system-level preparedness.

Research Limitations and Strengths

Several limitations should be considered when interpreting this study's findings. First, literature reviews can be subject to publication bias. Since null findings are less likely to be published, articles reporting associations between the influenza season and a given outcome are more likely to be identified in the literature. Second, since we conducted the secondary database analysis on aggregated data, its results do not necessarily represent the direct impact of influenza cases on NHS service provision. Moreover, we cannot draw causal inferences from these analyses. In addition, as participants reported on events that occurred up to four years earlier, the public survey may have been subject to recall bias. We cannot know whether this resulted in over or underestimation of these events' magnitude (e.g. lost wages and out-of-pocket costs).

Furthermore, our survey may have been subject to social desirability bias, particularly for questions around productivity (i.e. participants may have been reluctant to report that they were less productive at work). Thus, self-reported-productivity estimates may be inflated. In addition, NHS stakeholder interviews involved only a small number of individuals whose experiences and opinions may not reflect those of others in their department, region or the NHS generally. Nevertheless, the results aligned well with objective findings from our secondary database analyses. Lastly, the modelling output is only as good as the input parameters and overall modelling assumptions. While we are confident that our modelling values were reasonable, models often oversimplify complicated phenomena. Moreover, since the COVID-19 situation was uncertain, we modelled our scenarios based on our best judgement of how the “post-COVID” world might look. However, the true impact of COVID-19 on the future severity of the influenza season is unclear.

This study's main strengths are the use of multiple quantitative and qualitative methods and the cross-method triangulation of findings to better understand the societal impact of seasonal influenza and inform the development of epidemiologic and economic models quantifying indirect costs. Specifically, we employed a unique macro-economic modelling approach that accounts for the relationship between national economies and spillover effects across employment sectors—an advantage over traditional cost-estimation analyses. Lastly, we used a conservative approach to estimating economic modelling parameters to avoid overestimating potential costs.

Conclusions

The UK influenza season is associated with a substantial societal burden, including out-of-pocket costs and absenteeism (resulting in lost wages for many individuals) and presenteeism (resulting in lower productivity at work and increased workplace-transmission risks). In addition, increased demands on NHS services during the influenza season and higher NHS staff absenteeism and presenteeism disrupt routine services, especially in the secondary-care setting.

Assuming a “post-COVID” world where seasonal influenza infections increase again but do not reach pre-pandemic levels, our epidemiologic-economic modelling framework estimates that 2.4 million working adults could contract influenza annually, equating to 4.8 million lost working days annually. This translates to a £644m loss to the UK economy (0.04% of GDP). Modelling also showed that increasing vaccination rates in working adults by ten percentage points per employment sector could increase national GDP by £258m. Therefore, given seasonal influenza's considerable burden, we need strategies to mitigate its impact on the UK's population, NHS and economy.