Gripe estacional en España: carga clínica y económica y programas de vacunación

Disease burden of influenza in Spain: A five-season study (2015-2020)

Influenza accounts for 30% of the total morbidity and mortality in the European Union. However, the specific burden in different European countries is largely unknown, and more research is needed to ascertain the reality of this disease. In this retrospective study, we analyzed the burdens of hospitalization, intensive care unit (ICU) admission and in-hospital mortality in Spain over five seasons (2015-2020) via publicly available Minimum Basic Datasets (MDBS). The data revealed that influenza had a major impact in Spain, with approximately 29,000 hospitalizations, 2,200 ICU admissions, and 1,600 deaths each season. In this period, approximately 7.8% of those hospitalized required ICU admission, and 5.7% died in the hospital due to influenza, with wide differences in these parameters depending on the season due to the virological characteristics of the major circulating viruses. More than 60% of those hospitalized were over 65 years of age, and approximately 82% of those who died were elderly, demonstrating that the greatest burden of hospitalization and mortality is centered on this age group. The annual direct cost of influenza was approximately €128 million per season, with more than 80% of this cost centered on people over 45 years of age.

Critical assessment of uncertainty in economic evaluations on influenza vaccines for the elderly population in Spain

BACKGROUND

Influenza is a seasonal infection with a huge impact on morbidity and mortality in older adults, for whom vaccination is recommended. New influenza vaccines for this population have been introduced in Spain in the past 5 years, and a number of cost-effectiveness analyses (CEA) have been published to aid healthcare decision-making. The objective of this study was to assess possible sources of uncertainty in the CEAs of influenza vaccines for the older adults in Spain.

METHODS

A systematic review was performed to identify Spanish CEAs published since 2016. Potential sources of structural, methodologic and parametric uncertainty in CEA results were systematically analysed using the TRansparent Uncertainty ASsessmenT (TRUST) Tool, quality assessment checklists, and the WHO guidance on economic evaluations of influenza vaccine strategies. The primary sources of efficacy/effectiveness were analysed in depth to ascertain whether they could support the conclusions of the respective CEAs.

RESULTS

Seven CEAs were included. Overall, they were designed and performed in accordance with the applicable guidelines; however, some critical sources of uncertainty were detected, mainly: (1) the choice and use of efficacy/effectiveness data (real-world single season studies, meta-analyses including studies with high risk of bias and/or high heterogeneity with biased interpretation); (2) use of fewer than 5 seasons to estimate influenza burden; (3) generalized use of influenza-like illness data to estimate effectiveness and burden, among others.

CONCLUSIONS

Seemingly well-designed studies may conceal important sources of uncertainty that affect the results. This must be taken into account when interpreting results to support decision-making.

Factors associated to the presence of headache in patients with influenza infection and its consequences: a 2010-2020 surveillance-based study

Headache is a common symptom of influenza infection; however, its causes and consequences remain uncertain. In this manuscript, we analyzed which demographic and clinical factors were associated with the presence of headache during the course of influenza infection and whether patients with headache had a different prognosis, evaluated by need of hospitalization, sick leave or school absenteeism. The influence study (NCT05704335) was an observational study that analyzed data routinely collected from the Health Sentinel Network between 2010 and 2020. During the study period, 7832 cases were considered, among which, 5275 (67.4%) reported headache. The presence of headache was independently associated with myalgia (2.753; 95%CI: 2.456-3.087, P < 0.001), asthenia (OR: 1.958; 95%CI: 1.732-2.214, P < 0.001), shivering (OR: 1.925; 95%CI: 1.718-2.156, P < 0.001), nasopharyngeal erythema (OR: 1.505; 95%CI: 1.293-1.753, P < 0.001), fever (OR: 1.469; 95%CI: 1.159-1.861; P = 0.001), sudden onset of symptoms (OR: 1.380; 95%CI: 1.120-1.702, p = 0.004), female sex (OR: 1.134; 95%CI: 1.023-1.257, P = 0.018), and gastrointestinal symptoms (OR: 1.169; 95%CI: 1.039-1.315; P = 0.01). Patients with headache had a sex and age adjusted lower odds of being referred to the hospital (OR: 0.463; 95%CI: 0.264-0.812, P = 0.007) and a higher odd of having a sick leave and/or school absenteeism (absenteeism (OR: 1.342; 95%CI: 1.190-1.514, P < 0.001). In conclusion, the presence of headache seems associated with symptoms caused by the innate immune response. These findings support a headache pathophysiology linked with the innate immune response. Due to the potential negative consequences and its treatable nature, clinicians should systematically evaluate it and, whenever necessary, treat it too.

Old and new aspects of influenza

Influenza is a classic infectious disease that, through the continuous variation of the viruses that produce it, imposes new challenges that we must solve as quickly as possible. The COVID-19 pandemic has substantially modified the behavior of influenza and other respiratory viruses, and in the coming years we will have to coexist with a new pathogen that will probably interact with existing pathogens in a way that we cannot yet glimpse. However, knowledge prior to the pandemic allows us to focus on the aspects that must be modified to make influenza an acceptable challenge for the future. In this review, emphasis is placed on the most relevant aspects of epidemiology, disease burden, diagnosis, and vaccine prevention, and how scientific and clinical trends in these aspects flow from the previously known to future challenges.

Influenza hospitalisations in Spain between the last influenza and COVID-19 pandemic (2009-2019)

Knowing the burden of severe disease caused by influenza is essential for disease risk communication, to understand the true impact of vaccination programmes and to guide public health and disease control measures. We estimated the number of influenza-attributable hospitalisations in Spain during the 2010-2011 to 2019-2020 seasons - based on the hospitalisations due to severe acute respiratory infection (SARI) in Spain using the hospital discharge database and virological influenza information from the Spanish Influenza Sentinel Surveillance System (SISSS). The weekly numbers of influenza-attributable hospitalisations were calculated by multiplying the weekly SARI hospitalisations by the weekly influenza virus positivity, obtained from the SISSS in each season, stratified by age group and sex. The influenza-related hospitalisation burden is age-specific and varies significantly by influenza season. People aged 65 and over yielded the highest average influenza-attributable hospitalisation rates per season (615.6 per 100,000), followed by children aged under 5 (251.2 per 100,000). These results provide an essential contribution to influenza control and to improving existing vaccination programmes, as well as to the optimisation and planning of health resources and policies.

Excess hospitalizations and mortality associated with seasonal influenza in Spain, 2008-2018

BACKGROUND

Influenza may trigger complications, particularly in at-risk groups, potentially leading to hospitalization or death. However, due to lack of routine testing, influenza cases are infrequently coded with influenza-specific diagnosis. Statistical models using influenza activity as an explanatory variable can be used to estimate annual hospitalizations and deaths associated with influenza. Our study aimed to estimate the clinical and economic burden of severe influenza in Spain, considering such models.

METHODS

The study comprised ten epidemic seasons (2008/2009-2017/2018) and used two approaches: (i) a direct method of estimating the seasonal influenza hospitalization, based on the number of National Health Service hospitalizations with influenza-specific International Classification of Diseases (ICD) codes (ICD-9: 487-488; ICD-10: J09-J11), as primary or secondary diagnosis; (ii) an indirect method of estimating excess hospitalizations and deaths using broader groups of ICD codes in time-series models, computed for six age groups and four groups of diagnoses: pneumonia or influenza (ICD-9: 480-488, 517.1; ICD-10: J09-J18), respiratory (ICD-9: 460-519; ICD-10: J00-J99), respiratory or cardiovascular (C&R, ICD-9: 390-459, 460-519; ICD-10: I00-I99, J00-J99), and all-cause. Means, excluding the H1N1pdm09 pandemic (2009/2010), are reported in this study.

RESULTS

The mean number of hospitalizations with a diagnosis of influenza per season was 13,063, corresponding to 28.1 cases per 100,000 people. The mean direct annual cost of these hospitalizations was €45.7 million, of which 65.7% was generated by patients with comorbidities. Mean annual influenza-associated C&R hospitalizations were estimated at 34,894 (min: 16,546; max: 52,861), corresponding to 75.0 cases per 100,000 (95% confidence interval [CI]: 63.3-86.3) for all ages and 335.3 (95% CI: 293.2-377.5) in patients aged ≥ 65 years. We estimate 3.8 influenza-associated excess C&R hospitalizations for each hospitalization coded with an influenza-specific diagnosis in patients aged ≥ 65 years. The mean direct annual cost of the estimated excess C&R hospitalizations was €142.9 million for all ages and €115.9 million for patients aged ≥ 65 years. Mean annual influenza-associated all-cause mortality per 100,000 people was estimated at 27.7 for all ages.

CONCLUSIONS

Results suggest a relevant under-detected burden of influenza mostly in the elderly population, but not neglectable in younger people.

Austerity Measures and Underfunding of the Spanish Health System during the COVID-19 Pandemic-Perception of Healthcare Staff in Spain

Insufficient pandemic preparedness and underfunding of human and economic resources have conditioned the response to COVID-19 in Spain. This underfunding has continued since the austerity measures introduced during the 2008 financial crisis. This study aims to understand the perceptions of healthcare staff in Spain on the relationship between the funding of the health system and its capacity to respond to the COVID-19 pandemic. To this end, we carried out a thematic content analysis, based on 79 online semi-structured interviews with healthcare staff across the regions most affected by the COVID-19 first wave. Participants reported a lack of material resources, which had compromised the capacity of the health system before the pandemic. The lack of human resources was to be addressed by staff reorganisation, such as reinforcing hospital units to the detriment of primary health care. Staff shortages continued straining the COVID-19 response, even after material scarcities were later partially alleviated. Personnel shortages need to be adequately addressed in order to adequately respond to future health crises.

Clinical and economic burden of physician-diagnosed influenza in adults during the 2017/2018 epidemic season in Spain

BACKGROUND

Influenza is an acutely debilitating respiratory infection, contributing significantly to outpatient visits and hospitalizations. Spain lacks comprehensive and updated data on the burden of influenza, particularly in the outpatient setting. Our study aimed to fill this gap by estimating the clinical and economic burden of physician-diagnosed influenza cases in adults from four Spanish regions, stratified by age groups and presence of comorbidities.

METHODS

A retrospective cost-of-illness study was conducted using data from an electronic medical records database from the National Healthcare Service (NHS) of four Spanish regions for individuals aged ≥ 18 years diagnosed for influenza during the 2017/2018 epidemic season. Health resource utilization and related cost data were collected, including primary care visits, referrals to other specialists, visits to the emergency department, hospitalizations, and prescribed medicines.

RESULTS

The study reported a total of 28,381 patients aged ≥ 18 years diagnosed with influenza, corresponding to 1,804 cases per 100,000 population. Most patients were aged < 65 years: 60.5% (n = 17,166) aged 18-49 and 26.3% (n = 7,451) 50-64 years. A total of 39.2% (n = 11,132) of patients presented a comorbidity. Cardiovascular diseases were the most common comorbidity reported along with influenza. The mean healthcare cost per case was estimated at €235.1 in population aged 18-49 years, increasing by 1.7 and 4.9 times in those aged 50-64 (€402.0) and ≥ 65 (€1,149.0), respectively. The mean healthcare cost per case was 3.2 times higher in patients with comorbidities. The total healthcare cost of medically attended influenza cases was mainly driven by primary care (45.1%) and hospitalization (42.0%). Patients aged 18-64 years old accounted for 61.9% of the costs of medically attended influenza. Irrespective of age, patients with comorbidities accounted for 67.1% of costs.

CONCLUSIONS

Season 2017/2018 was associated with a considerable burden of influenza in Spain, which increased with age and presence of comorbidities. Individuals with comorbidities accounted for most of the costs of influenza. Results suggest that population aged 18-64 years old is generating the highest share of costs to the NHS when all healthcare costs are considered. Preventive strategies targeting subjects with comorbidities, regardless of age, should be warranted.

Attitudes, Perceptions and Practices of Influenza Vaccination in the Adult Population: Results of a Cross-Sectional Survey in Spain

In Spain, the 2021/22 influenza season overlapped with the sixth wave of the 2019 coronavirus disease pandemic (COVID-19). Influenza is a major public health problem associated with high morbidity and mortality. The objectives of this study were to determine the knowledge, perceptions and practices of influenza vaccination in the Spanish population, coinciding with the COVID-19 pandemic, with special attention paid to people over 65 years of age. A cross-sectional study was carried out by conducting 2211 telephone interviews. It was observed that 81.6% of people ≥ 65 years were vaccinated annually or with some frequency compared to 35.5% of those under 65 years (p < 0.001). Fifty percent of Spaniards showed an intention to be vaccinated in the 2021/22 campaign, during the SARS-CoV2 pandemic. In the case of people ≥ 65 years old, this figure was 83% compared to 42% of those under 65 years old (p < 0.001). Significant predictors of intention to be vaccinated were age of 65 years or older (OR 1.8, 95% CI 1.3-2.5), female sex (OR 1.9, 95% CI 1.5-2.4), belonging to risk groups (OR 2.2, 95% CI 1.6-3.1) and having been previously vaccinated (OR 29.7, 95% CI 22.5-39.2). The main reasons for deciding to be vaccinated were the need to be protected against the virus and to be vaccinated annually. On the other hand, lack of recommendation and considering the influenza vaccine as not necessary were the main reasons for not getting vaccinated. In addition, health personnel stood out as the main source of information (32.9%) compared to traditional media (26.9%) and public administration (12.3%). This study aimed to assess and analyse the factors influencing willingness to receive influenza vaccines in the COVID-19 era among Spanish adults, as well as the main information channels and strategies to encourage vaccination.

Effect of vaccination on the prevention of influenza-related severe illness in adults attended in a third level hospital during the 2017-2018 epidemic season

OBJECTIVES

The objective of this research was to evaluate the effect of influenza vaccination on the prevention of influenza-related severe cases in adults treated in a third-level hospital during the 2017-2018 epidemic season.

METHODOLOGY

A descriptive analysis was performed on the entire population of subjects with a laboratory-confirmed influenza test during the 2017-2018 season. A severe case was defined as a patient treated in one of the Intensive Care Units (ICUs) and/or death. The effect of the vaccine on the adult population was determined by multivariate logistic regression analysis.

RESULTS

Between epidemiological weeks 44/2017 and 19/2018, the hospital's laboratory detected 706 positive samples for influenza virus. Of the 551 confirmed patients aged 18 years or older, forty-three were admitted to one of the ICUs, and 26 died during admission. The explanatory multivariate model has shown that flu vaccination prior to or during the epidemic season was a protective factor for the development of severity [OR:0.27 (0.11-0.65, p=0.004)], adjusted by age [OR: 1.03 (1.01-1.06), p=.04], sex, type of virus (H1N1-pdm09, H3N2 or B virus), Chronic Complex Patient index or Advanced Chronic Disease index.

CONCLUSSIONS

Influenza vaccination is a protective factor against the development of severity associated with influenza infection in a season when vaccination did not contain the virus with higher epidemic circulation among the population. Flu vaccination should be recommended annually following the guidelines established by the health authorities.

From trivalent to quadrivalent influenza vaccines: Public health and economic burden for different immunization strategies in Spain

PURPOSE

Quadrivalent influenza vaccine (QIV) includes the same strains as trivalent influenza vaccine (TIV) plus an additional B strain of the other B lineage. The aim of the study was to analyse the public health and economic impact of replacing TIV with QIV in different scenarios in Spain.

METHODS

A dynamic transmission model was developed to estimate the number of influenza B cases prevented under TIV and QIV strategies (<65 years (high risk) and ≥65 years). This model considers cross-protective immunity induced by different lineages of influenza B. The output of the transmission model was used as input for a decision tree model that estimated the economic impact of switching TIV to QIV. The models were populated with Spanish data whenever possible. Deterministic univariate and probabilistic multivariate sensitivity analyses were performed.

RESULTS

Replacing TIV with QIV in all eligible patients with current vaccine coverage in Spain may have prevented 138,707 influenza B cases per season and, therefore avoided 10,748 outpatient visits, 3,179 hospitalizations and 192 deaths. The replacement could save €532,768 in outpatient visit costs, €13 million in hospitalization costs, and €3 million in costs of influenza-related deaths per year. An additional €5 million costs associated with productivity loss could be saved per year, from the societal perspective. The budget impact from societal perspective would be €6.5 million, and the incremental cost-effectiveness ratio (ICER) €1,527 per quality-adjusted life year (QALY). Sensitivity analyses showed robust results. In additional scenarios, QIV also showed an impact at public health level reducing influenza B related cases, outpatient visits, hospitalizations and deaths.

CONCLUSIONS

Our results show public health and economic benefits for influenza prevention with QIV. It would be an efficient intervention for the Spanish National Health Service with major health benefits especially in the population ≥65-year.