Review of seasonal influenza in Canada: Burden of disease and the cost-effectiveness of quadrivalent inactivated influenza vaccines

Clinical characteristics of outpatients with influenza-B-associated pneumonia and molecular evolution of influenza B virus in Beijing, China, during the 2021-2022 influenza season

We analyzed the clinical characteristics of outpatients with influenza-B-associated pneumonia during the 2021-2022 influenza season and analyzed the molecular epidemiology and evolution of influenza B virus. The presence of influenza B virus was confirmed by reverse transcription polymerase chain reaction (RT-PCR). Electronic medical records were used to collect and analyze data of outpatients. The HA and NA genes were phylogenetically analyzed using ClustalW 2.10 and MEGA 11.0. Out of 1569 outpatients who tested positive for influenza B virus, 11.7% (184/1569) developed pneumonia, and of these, 19.0% (35/184) had underlying diseases. Fever, cough, and sore throat were the most common symptoms. Among the complications, acute respiratory distress syndrome (ARDS), acute kidney injury (AKI), and shock accounted for 2.7% (5/184), 4.9% (9/184), and 1.6% (3/184), respectively. Of the outpatients, 2.7% (5/184) were admitted to the hospital, and 0.5% (1/184) of them died. All of the strains from Beijing were identified as belonging to the B/Victoria lineage. The HA and NA gene sequences of 41 influenza B viruses showed high similarity to each other, and all of them belonged to clade 1A.3. Compared with the vaccine strain B/Washington/02/2019, all of the isolates contained N150K, G181E, and S194D mutations. S194D, E195K, and K200R mutations were detected in the 190 helix of the receptor binding region of HA. Co-mutations of H122Q, A127T, P144L, N150K, G181E, S194D, and K200R in HA and D53N, N59S, and G233E in NA were detected in 78.0% (32/41) of the isolates, and 56.3% (18/32) of these were from outpatients with influenza-B-associated pneumonia. Influenza outpatients with underlying diseases were more likely to develop pneumonia. No significant differences were observed in clinical symptoms or laboratory results between outpatients with and without pneumonia, so testing for influenza virus seems to be a good choice. The observed amino acid variations suggest that current vaccines might not provide effective protection.

A review of policies and coverage of seasonal influenza vaccination programs in the WHO Eastern Mediterranean Region

Background

Although there has been an effective seasonal influenza vaccine available for more than 60 years, influenza continues to circulate and cause illness. The Eastern Mediterranean Region (EMR) is very diverse in health systems capacities, capabilities, and efficiencies, which affect the performance of services, especially vaccination, including seasonal influenza vaccination.

Aims

The aim of this study is to provide a comprehensive overview on country‐specific influenza vaccination policies, vaccine delivery, and coverage in EMR.

Materials and Methods

We have analyzed data from a regional seasonal influenza survey conducted in 2022, Joint Reporting Form (JRF), and verified their validity by the focal points. We also compared our results with those of the regional seasonal influenza survey conducted in 2016.

Results

Fourteen countries (64%) had reported having a national seasonal influenza vaccine policy. About (44%) countries recommended influenza vaccine for all SAGE recommended target groups. Up to 69% of countries reported that COVID‐19 had an impact on influenza vaccine supply in the country, with most of them (82%) reporting increases in procurement due to COVID‐19.

Discussion

The situation of seasonal influenza vaccination in EMR is varied, with some countries having well established programs while others having no policy or program; these variances may be due to resources inequity, political, and socioeconomic dissimilarities. Few countries have reported wide vaccination coverage over time with no clear trend of improvement.

Conclusion

We suggest supporting countries to develop a roadmap for influenza vaccine uptake and utilization, assessment of barriers, and burden of influenza, including measuring the economic burden to enhance vaccine acceptance.

Economic evaluation of COVID-19 rapid antigen screening programs in the workplace

BACKGROUND

Diagnostic testing has been pivotal in detecting SARS-CoV-2 infections and reducing transmission through the isolation of positive cases. We quantified the value of implementing frequent, rapid antigen (RA) testing in the workplace to identify screening programs that are cost-effective.

METHODS

To project the number of cases, hospitalizations, and deaths under alternative screening programs, we adapted an agent-based model of COVID-19 transmission and parameterized it with the demographics of Ontario, Canada, incorporating vaccination and waning of immunity. Taking into account healthcare costs and productivity losses associated with each program, we calculated the incremental cost-effectiveness ratio (ICER) with quality-adjusted life year (QALY) as the measure of effect. Considering RT-PCR testing of only severe cases as the baseline scenario, we estimated the incremental net monetary benefits (iNMB) of the screening programs with varying durations and initiation times, as well as different booster coverages of working adults.

RESULTS

Assuming a willingness-to-pay threshold of CDN$30,000 per QALY loss averted, twice weekly workplace screening was cost-effective only if the program started early during a surge. In most scenarios, the iNMB of RA screening without a confirmatory RT-PCR or RA test was comparable or higher than the iNMB for programs with a confirmatory test for RA-positive cases. When the program started early with a duration of at least 16 weeks and no confirmatory testing, the iNMB exceeded CDN$1.1 million per 100,000 population. Increasing booster coverage of working adults improved the iNMB of RA screening.

CONCLUSIONS

Our findings indicate that frequent RA testing starting very early in a surge, without a confirmatory test, is a preferred screening program for the detection of asymptomatic infections in workplaces.

Risk factors and medical resource utilization in US adults hospitalized with influenza or respiratory syncytial virus in the Hospitalized Acute Respiratory Tract Infection study

Background

Influenza and respiratory syncytial virus (RSV) are associated with substantial morbidity and mortality in the United States. We assessed risk factors for severe disease and medical resource utilization (MRU) among US adults hospitalized with influenza or RSV in the Hospitalized Acute Respiratory Tract Infection (HARTI) study.

Methods

HARTI was a prospective global (40 centers, 12 countries) epidemiological study of adults hospitalized with acute respiratory tract infections conducted across the 2017–2019 epidemic seasons. Patients with confirmed influenza or RSV were followed up to 3 months post‐discharge. Baseline characteristics, prevalence of core risk factors (CRFs) for severe disease (age ≥65 years, chronic heart or renal disease, chronic obstructive pulmonary disease, or asthma), and MRU were summarized descriptively.

Results

The US cohort included 280 influenza‐positive and 120 RSV‐positive patients. RSV patients were older (mean: 63.1 vs. 59.7 years) and a higher proportion had CRFs (87.5% vs. 81.4%). Among those with CRFs (influenza, n = 153; RSV, n = 99), RSV patients required longer hospitalizations (median length of stay: 4.5 days) and a greater proportion (79.8%) required oxygen supplementation during hospitalization compared with influenza patients (4.0 days and 59.5%, respectively). At 3 months post‐discharge, a greater proportion of RSV patients with CRFs reported use of antibiotics, antitussives, bronchodilators, and inhaled and systemic steroids versus those with influenza and CRFs. Many patients with CRFs reported hospital readmission at 3 months post‐discharge (RSV: 13.4%; influenza: 11.9%).

Conclusions

MRU during and post‐hospitalization due to RSV in adults is similar to or greater than that of influenza. Enhanced RSV surveillance and preventive and therapeutic interventions are needed.

Clinical and virological impact of single and dual infections with influenza A (H1N1) and SARS-CoV-2 in adult inpatients

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mimics the influenza A (H1N1) virus in terms of clinical presentation, transmission mechanism, and seasonal coincidence. Comprehensive data for the clinical severity of adult patients co-infected by both H1N1 and SARS-CoV-2, and, particularly, the relationship with PCR cycle threshold (Ct) values are not yet available. All participants in this study were tested for H1N1 and SARS-CoV-2 simultaneously at admission. Demographic, clinical, treatment, and laboratory data were extracted from electronic medical records and compared among adults hospitalized for H1N1 infection, SARS-CoV-2 infection and co-infection with both viruses. Ct values for viral RNA detection were further compared within SARS-CoV-2 and co-infection groups. Score on seven-category ordinal scale of clinical status at day 7 and day 14 were assessed. Among patients with monoinfection, H1N1 infection had higher frequency of onset symptoms but lower incidence of adverse events during hospitalization than SAR-CoV-2 infection (P < 0.05). Co-infection had an increased odds of acute kidney injury, acute heart failure, secondary bacterial infections, multilobar infiltrates and admittance to ICU than monoinfection. Score on seven-category scale at day 7 and day 14 was higher in patients with coinfection than patients with SAR-CoV-2 monoinfection (P<0.05). Co-infected patients had lower initial Ct values (referring to higher viral load) (median 32) than patients with SAR-CoV-2 monoinfection (median 36). Among co-infected patients, low Ct values were significantly and positively correlated with acute kidney injury and ARDS (P = 0.03 and 0.02, respectively). Co-infection by SARS-CoV-2 and H1N1 caused more severe disease than monoinfection by either virus in adult inpatients. Early Ct value could provide clues for the later trajectory of the co-infection. Multiplex molecular diagnostics for both viruses and early assessment of SAR-CoV-2 Ct values are recommended to achieve optimal treatment for improved clinical outcome.

The baseline enrolled 505 patients admitted to Guangzhou Eighth People’s Hospital (Guangzhou, Guangdong) with a diagnosis of COVID-19 or H1N1. All the patients were tested by both viruses at admission. Demographic, clinical, treatment, and laboratory data were extracted from electronic medical records and compared among adults (≥18 years) hospitalized for H1N1 infection (n = 220), SARS-CoV-2 infection (n = 249) and co-infection with both viruses (n = 36). The prevalence rate of H1N1 co-infection was 12.6% (36/285) among patients hospitalized with COVID-19. Co-infection affected a predominantly older age group and was associated with poorer clinical outcome. We also described the viral load trajectory in patients with diverse types of infection. Lower initial Ct values (higher viral loads in nasopharyngeal swabs) of co-infected patients was found to be associated with a higher number of adverse events and clinical symptoms. Considering the COVID-19 pandemic and a simultaneous epidemic of seasonal influenza, the data in China may critically inform future therapeutic or prophylactic strategies, especially for other developing countries.

Survival in influenza virus-related pneumonia by viral subtype: 2016-2020

BACKGROUND

Influenza remains a common cause of morbidity and mortality worldwide, and viral subtype-related differences in disease outcomes have been documented.

OBJECTIVE

To characterize the survival experience of adult inpatients with influenza virus-associated pneumonia by viral subtype during five consecutive flu seasons.

METHOD

We performed a retrospective cohort study; data from 4,678 adults were analyzed using the Kaplan-Meier method. A multivariate Cox proportional hazard regression model was fitted.

RESULTS

The overall in-hospital mortality rate was 25.0 per 1,000 hospital days. The survival probabilities from pneumonia patients went from 93.4% (95% CI 92.6-94.1%) by day three to 43.3% (95% CI 39.2-47.4%) by day 30 from hospital admission. In general, the lowest survival rates were observed in patients with AH1N1 infection. In multiple models, after adjusting for comorbidities and when compared with A non-subtyped virus, pneumonia patients with AH3N2 or B strains had a significantly decreased risk of a non-favorable disease outcome. The association of other strains was not significant.

CONCLUSIONS

Our findings suggest that the survival of inpatients with influenza virus-associated pneumonia varies according to the pathogenic viral subtype; the lowest survival rates were observed in patients with AH1N1 infection. This effect was independent of the patients' gender, age, and the analyzed underlying health conditions.

No effect modification of influenza virus vaccine effectiveness by age or chronic condition was observed in the 2010/11 to 2017/18 seasons

PURPOSE

Most European influenza vaccine strategies target individuals at higher risk of complications, which include, among others, individuals aged ≥65 years and with chronic conditions. These individuals not only have a high-risk of post-infection complications but also could have lower capacity of acquiring adequate vaccine-induced protection. As such, chronic conditions and age could modify the effect of vaccines. This study aimed at assessing the potential effect modification of influenza vaccine effectiveness (IVE) by age and chronic conditions.

METHODS

We used eight-season data from the Portuguese vaccine effectiveness study. Every season, physicians at primary care units recruited patients with influenza-like illness. Clinical data and swabs were collected for Reverse Transverse Polymerase Chain Reaction (RT-PCR) detection of influenza. Trivalent inactivated IVE was estimated as 1 - odds ratio (OR) of being vaccinated in cases (RT-PCR positive for influenza) versus negative controls. ORs were obtained using a multivariable conditional logistic regression model, paired by week of onset within each season. Confounders were assessed by designing a specific causal diagram. Age (< 65 or ≥65 years) and chronic conditions (diabetes, cardiovascular disease, chronic renal disease, chronic hepatic disease, obesity, chronic respiratory disease, and congenital or acquired immunodeficiency) were studied as effect modifiers by including an interaction term in the regression models. Significance was established at 5%.

RESULTS

Point estimates indicate a higher IVE in the chronic condition strata compared to that in the no chronic condition strata. Regarding age, different results were obtained considering the virus type and (sub)type. When comparing the ≥65 years with the <65 years of age strata, we observed a higher IVE against A(H1N1)pdm09, an equal IVE against A(H3N2) and a lower IVE against B virus. However, all interaction terms were statistically insignificant, and this may be due to a small sample size.

CONCLUSION

The potential effect modification of age or chronic condition was not observed within our study.

Cost-Effectiveness Analysis of Switching from Trivalent to Quadrivalent Seasonal Influenza Vaccine in Argentina

The burden of seasonal influenza disease in Argentina is considerable. The cost-effectiveness of trivalent (TIV) versus quadrivalent influenza vaccine (QIV) in Argentina was assessed. An age-stratified, static, decision-tree model compared the costs and benefits of vaccination for an average influenza season. Main outcomes included: numbers of influenza cases; general practitioner (GP) visits; complicated ambulatory cases; hospitalizations; deaths averted; and costs per quality-adjusted life years (QALYs) gained. Epidemiological data from Argentina for 2014–2019 were used to determine the proportion of A and B strain cases, and the frequency of mismatch between vaccine and circulating B strains. To manage uncertainty, one-way and probabilistic sensitivity analyses were performed. Switching from TIV to QIV would prevent 19,128 influenza cases, 16,164 GP visits, 2440 complicated ambulatory cases, 524 hospitalizations, and 82 deaths. Incremental cost–effectiveness ratios (ICERs) per QALY were 13,590 and 11,678 USD from the payer’s and societal perspectives, respectively. The greatest health benefits and direct medical cost savings would occur in ≥ 65-year-olds. One-way sensitivity analyses demonstrated the principal drivers of ICER to be vaccine acquisition costs, environmental B strain predominance, and B strain mismatch. Introducing QIV in Argentina would be beneficial and cost-effective relative to TIV, particularly in older adults.

Inclusion of Safety-Related Issues in Economic Evaluations for Seasonal Influenza Vaccines: A Systematic Review

(1) Background: Vaccines for seasonal influenza are a good preventive and cost-effective strategy. However, it is unknown if and how these economic evaluations include the adverse events following immunization (AEFI), and what the impact of such inclusion is on the health economic outcomes. (2) Methods: We searched the literature, up to January 2020, to identify economic evaluations of seasonal influenza vaccines that considered AEFIs. The review protocol was published in PROSPERO (CDR42017058523). (3) Results: A total of 52 economic evaluations considered AEFI-related parameters in their analyses, reflecting 16% of the economic evaluations on seasonal influenza vaccines in the initial study selection. Most studies used the societal perspective (64%) and evaluated vaccination of children (37%). Where considered, studies included direct medical costs of AEFIs (90%), indirect costs (27%), and disutilities/quality-adjusted life years loss due to AEFIs (37%). The majority of these studies accounted for the effects of the costs of AEFI on cost-effectiveness for Guillain–Barré syndrome. In those papers allowing cost share estimation, direct medical cost of AFEIs was less than 2% of total direct costs. (4) Conclusions: Although the overall impact of AEFIs on the cost-effectiveness outcomes was found to be low, we urge their inclusion in economic evaluations of seasonal influenza vaccines to reflect comprehensive reports for the decision makers and end-users of the vaccination strategies.

Novel Use of Rapid Antigen Influenza Testing in the Outpatient Setting To Provide an Early Warning Sign of Influenza Activity in the Emergency Departments of an Integrated Health System

Seasonal influenza virus is associated with high morbidity and mortality especially in vulnerable patient populations. Here, we demonstrate the novel use of Sofia influenza A+B fluorescent immunoassay (FIA), a rapid antigen-based influenza point-of-care test (POCT), combined with Virena software for automatic deidentified tracking of influenza activity across the Los Angeles area and for predicting surges of influenza cases in the emergency department (ED). We divided outpatient clinics into 6 geographic zones and compared weekly influenza activity. In the outpatient setting, there were 1,666 and 274 influenza A and influenza B positives, respectively, across the 2018 to 2019 influenza season and 1,857 and 1,449 influenza A and influenza B positives, respectively, during the 2019 to 2020 influenza season, with zone-specific differences observed. Moreover, we found that a rapid increase in outpatient influenza was followed by an influx in influenza-positive cases in the ED, offering a 1- to 3-week warning sign for ED influx of triple or quadruple the number of influenza cases compared to the prior week. Sofia influenza A+B FIA allows for surveillance of real-time deidentified influenza activity. Tracking of such data may serve as a valuable region-specific influenza indicator and predictor to guide infection prevention measures in both the outpatient and hospital settings. High-impact interventions include designating areas for waiting rooms for influenza-like illnesses, altering staff scheduling in anticipation of surges, and securing sufficient personal protective equipment and antivirals during the height of influenza season.

Frailty Hinders Recovery From Influenza and Acute Respiratory Illness in Older Adults

BACKGROUND

We examined frailty as a predictor of recovery in older adults hospitalized with influenza and acute respiratory illness.

METHODS

A total of 5011 patients aged ≥65 years were admitted to Canadian Serious Outcomes Surveillance Network hospitals during the 2011/2012, 2012/2013, and 2013/2014 influenza seasons. Frailty was measured using a previously validated frailty index (FI). Poor recovery was defined as death by 30 days postdischarge or an increase of more than 0.06 (≥2 persistent new health deficits) on the FI. Multivariable logistic regression controlled for age, sex, season, influenza diagnosis, and influenza vaccination status.

RESULTS

Mean age was 79.4 (standard deviation = 8.4) years; 53.1% were women. At baseline, 15.0% (n = 750) were nonfrail, 39.3% (n = 1971) were prefrail, 39.8% (n = 1995) were frail, and 5.9% (n = 295) were most frail. Poor recovery was experienced by 21.4%, 52.0% of whom had died. Frailty was associated with lower odds of recovery in all 3 seasons: 2011/2012 (odds ratio [OR] = 0.70; 95% confidence interval [CI], 0.59-0.84), 2012/2013 (OR = 0.72; 95% CI, 0.66-0.79), and 2013/2014 (OR = 0.75; 95% CI, 0.69-0.82); results varied by season, influenza status, vaccination status, and age.

CONCLUSIONS

Increasing frailty is associated with lower odds of recovery, and persistent worsening frailty is an important adverse outcome of acute illness.

Frailty Hinders Recovery From Influenza and Acute Respiratory Illness in Older Adults

BACKGROUND

We examined frailty as a predictor of recovery in older adults hospitalized with influenza and acute respiratory illness.

METHODS

A total of 5011 patients aged ≥65 years were admitted to Canadian Serious Outcomes Surveillance Network hospitals during the 2011/2012, 2012/2013, and 2013/2014 influenza seasons. Frailty was measured using a previously validated frailty index (FI). Poor recovery was defined as death by 30 days postdischarge or an increase of more than 0.06 (≥2 persistent new health deficits) on the FI. Multivariable logistic regression controlled for age, sex, season, influenza diagnosis, and influenza vaccination status.

RESULTS

Mean age was 79.4 (standard deviation = 8.4) years; 53.1% were women. At baseline, 15.0% (n = 750) were nonfrail, 39.3% (n = 1971) were prefrail, 39.8% (n = 1995) were frail, and 5.9% (n = 295) were most frail. Poor recovery was experienced by 21.4%, 52.0% of whom had died. Frailty was associated with lower odds of recovery in all 3 seasons: 2011/2012 (odds ratio [OR] = 0.70; 95% confidence interval [CI], 0.59-0.84), 2012/2013 (OR = 0.72; 95% CI, 0.66-0.79), and 2013/2014 (OR = 0.75; 95% CI, 0.69-0.82); results varied by season, influenza status, vaccination status, and age.

CONCLUSIONS

Increasing frailty is associated with lower odds of recovery, and persistent worsening frailty is an important adverse outcome of acute illness.

Severity and outcomes of influenza-related pneumonia in type A and B strains in China, 2013-2019

Background

Inconsistencies exist regarding the severity of illness caused by different influenza strains. The aim of this study was to compare the clinical outcomes of hospitalized adults and adolescents with influenza-related pneumonia (Flu-p) from type A and type B strains in China.

Methods

We retrospectively reviewed data from Flu-p patients in five hospitals in China from January 2013 to May 2019. Multivariate logistic and Cox regression models were used to assess the effects of influenza virus subtypes on clinical outcomes, and to explore the risk factors of 30-day mortality for Flu-p patients.

Results

In total, 963 laboratory-confirmed influenza A-related pneumonia (FluA-p) and 386 influenza B-related pneumonia (FluB-p) patients were included. Upon adjustment for confounders, multivariate logistic regression models showed that FluA-p was associated with an increased risk of invasive ventilation (adjusted odds ratio [aOR]: 3.824, 95% confidence interval [CI]: 2.279–6.414; P <  0.001), admittance to intensive care unit (aOR: 1.630, 95% CI: 1.074–2.473, P = 0.022) and 30-day mortality (aOR: 2.427, 95% CI: 1.568–3.756, P <  0.001) compared to FluB-p. Multivariate Cox regression models confirmed that influenza A virus infection (hazard ratio: 2.637, 95% CI: 1.134–6.131, P = 0.024) was an independent predictor for 30-day mortality in Flu-p patients.

Conclusions

The severity of illness and clinical outcomes of FluA-p patients are more severe than FluB-p. This highlights the importance of identifying the virus strain during the management of severe influenza.

Impact of early neuraminidase inhibitor treatment on clinical outcomes in patients with influenza B-related pneumonia: a multicenter cohort study

The aim of this study is to evaluate the impact of early (within 2 days after disease onset) neuraminidase inhibitor (NAI) administration on clinical outcomes in patients with laboratory-confirmed influenza B-related pneumonia (FluB-p). This was a multicenter study conducted from 1 January 2013 to 1 May 2019. Data of immunocompetent adult and adolescent FluB-p patients hospitalized at five different teaching hospitals in China were retrospectively collected, including demographic and clinical features as well as clinical and treatment outcomes. Univariate and multivariate logistic regression analyses were performed to assess the effects of early NAI administration on clinical outcomes in FluB-p patients. In total, 386 hospitalized patients with community-onset FluB-p were included in this study, of whom 39.6% (153/386) were treated with NAI early. After adjusting for the weighted propensity scores of treatment, systemic corticosteroid, and antibiotic uses, the results of multivariate logistic regression model indicated that early NAI treatment was associated with the decreased risks of invasive ventilation [odd ratio (OR) 0.325, 95% confidence interval (CI) 0.123-0.858; p = 0.023), admittance to intensive care unit (OR 0.425, 95% CI 0.204-0.882; p = 0.022), and 30-day mortality (OR 0.416, 95% CI 0.184-0.944, p = 0.036)] in FluB-p patients. In addition, the multivariate logistic regression analysis revealed that early NAI treatment (OR 0.306, 95% CI 0.063-0.618; p = 0.010) was an independent predictor for 30-day mortality in patients with FluB-p. Early NAI treatment was associated with better clinical outcomes in FluB-p patients, which supports the recommendations of its use in severe influenza illness.

Massive air leak secondary to influenza B in a 7-year-old: A case report

Influenza is an illness that affects individuals of all ages but its severity varies immensely: from the symptoms of a common cold to the deadly outbreak of the pandemic H1N1 strain in 2009. This case report describes the circumstances surrounding the critical illness of a healthy 7-year-old child who developed a massive air leak syndrome secondary to influenza B. She required the emergent insertion of a chest tube as well as intubation and mechanical ventilation. She developed severe acute respiratory distress syndrome and was strongly considered for being placed on extracorporeal membrane oxygenation. She was treated with ceftriaxone and oseltamivir and slowly improved over the course of 20 days. The purpose of this report is to illustrate the severity of influenza with an emphasis on prevention with vaccination.

Cost-Effectiveness Analysis for Influenza Vaccination Coverage and Timing in Tropical and Subtropical Climate Settings: A Modeling Study

BACKGROUND

The lack of seasonality in influenza epidemics in the tropics makes the application of well-established temperate zone national vaccination plans challenging.

OBJECTIVES

We developed an individual-based simulation model to study optimal vaccination scheduling and assess cost-effectiveness of these vaccination schedules in scenarios of no influenza seasonality and the seasonality regimes of Singapore, Taipei, and Tokyo.

METHODS

The simulation models heterogeneities in human contact networks, levels of protective antibodies following infection, the effectiveness of the influenza vaccine, and seasonality. Using a no intervention baseline, we consider 3 alternative vaccination strategies: (1) annual vaccination for a percentage of the elderly, (2) biannual vaccination for a percentage of the elderly, and (3) annual vaccination for all elderly and a fraction of the remaining population. We considered 5 vaccination uptake rates for each strategy and modeled the estimated costs, quality-adjusted life years, and incremental cost-effectiveness ratios (ICERs), indicating the cost-effectiveness of each scenario.

RESULTS

In Singapore, annual vaccination for a proportion of elderly is largely cost-effective. However, with fixed uptake rates, partial biannual vaccination for the elderly yields a higher ICER than partial annual vaccination for the elderly, resulting in a cost-ineffective ICER. The most optimal strategy is the total vaccination of all the elderly and a proportion of individuals from other age groups, which results in a cost-saving ICER. This finding is consistent across different seasonality regimes.

CONCLUSIONS

Tropical countries like Singapore can have comparably cost-effective vaccination strategies as found in countries with winter epidemics. The vaccination of all the elderly and a proportion of other age groups is the most cost-effective strategy, supporting the need for an extensive national influenza vaccination program.

Cost-effectiveness of quadrivalent versus trivalent influenza vaccine for elderly population in China

BACKGROUND

Influenza-associated excess death occurred most in the elderly. We aimed to assess the cost-effectiveness of quadrivalent influenza vaccine (QIV) versus trivalent influenza vaccine (TIV) for prevention of influenza infection among elderly population in China.

METHODS

A decision-analytic model was developed to compare 1-year clinical and economic outcomes of three influenza vaccination options (no vaccination, TIV, and QIV) in a hypothetical cohort of Chinese elderly aged 69 years. Outcome measures included cost, influenza infection rate, influenza-related mortality rate, quality-adjusted life-years (QALY) loss, and incremental cost-effectiveness ratio (ICER) from societal perspective. Sensitivity analyses were performed to examine the uncertainty of model inputs.

RESULTS

Base-case results showed no vaccination was dominated (more costly at higher QALY loss) by TIV and QIV. QIV was more costly (USD56.29 versus USD54.28) with lower influenza infection rate (0.608 versus 0.623), mortality rate (0.00199 versus 0.00204), and QALY loss (0.01213 versus 0.01243) than TIV. QIV was cost-effective compared to TIV with ICER of 6,700 USD/QALY below the willingness-to-pay threshold (29,580 USD/QALY). One-way sensitivity analysis found the cost-effectiveness of QIV was subject to the relative risk of vaccine effectiveness of QIV versus TIV, and TIV would be cost-effective if the relative risk was below 1.05. In 10,000 Monte Carlo simulations, the probabilities of QIV, TIV, and no vaccination to be cost-effective were 86.3%, 13.7%, and 0%, respectively.

CONCLUSION

QIV appears to be a cost-effective option compared to TIV and no influenza vaccination for elderly population in China.

Burden of influenza-associated respiratory hospitalizations in the Americas, 2010-2015

BACKGROUND

Despite having influenza vaccination policies and programs, countries in the Americas underutilize seasonal influenza vaccine, in part because of insufficient evidence about severe influenza burden. We aimed to estimate the annual burden of influenza-associated respiratory hospitalizations in the Americas.

METHODS

Thirty-five countries in the Americas with national influenza surveillance were invited to provide monthly laboratory data and hospital discharges for respiratory illness (International Classification of Diseases 10th edition J codes 0-99) during 2010-2015. In three age-strata (<5, 5-64, and ≥65 years), we estimated the influenza-associated hospitalizations rate by multiplying the monthly number of respiratory hospitalizations by the monthly proportion of influenza-positive samples and dividing by the census population. We used random effects meta-analyses to pool age-group specific rates and extrapolated to countries that did not contribute data, using pooled rates stratified by age group and country characteristics found to be associated with rates.

RESULTS

Sixteen of 35 countries (46%) contributed primary data to the analyses, representing 79% of the America's population. The average pooled rate of influenza-associated respiratory hospitalization was 90/100,000 population (95% confidence interval 61-132) among children aged <5 years, 21/100,000 population (13-32) among persons aged 5-64 years, and 141/100,000 population (95-211) among persons aged ≥65 years. We estimated the average annual number of influenza-associated respiratory hospitalizations in the Americas to be 772,000 (95% credible interval 716,000-829,000).

CONCLUSIONS

Influenza-associated respiratory hospitalizations impose a heavy burden on health systems in the Americas. Countries in the Americas should use this information to justify investments in seasonal influenza vaccination-especially among young children and the elderly.

The National Influenza Surveillance System of Korea

Influenza is a very important respiratory infectious disease that causes seasonal epidemics and pandemics. A well-organized surveillance system is necessary to monitor and respond effectively to the epidemiologic features of influenza. Korea currently operates a national influenza surveillance system based on the clinical sentinel surveillance system, laboratory sentinel surveillance system, and hospitalization and mortality surveillance system. However, there is a need for a better national surveillance system due to a demand for various pieces of information related to influenza. This article discusses the general aspects of influenza surveillance systems and the future direction of the national influenza surveillance system of Korea.

Cost Effectiveness of Quadrivalent Influenza Vaccines Compared with Trivalent Influenza Vaccines in Young Children and Older Adults in Korea

INTRODUCTION

Trivalent influenza vaccines (TIVs) are currently reimbursed for subjects aged ≥ 65 years and children between 6 and 59 months of age under a national immunization program in South Korea. Quadrivalent influenza vaccines (QIVs) are expected to address the potential problem of influenza B-lineage mismatch for TIVs.

OBJECTIVE

The objective of this analysis was to compare the cost effectiveness of QIV versus TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea.

METHODS

A 1-year static population model was employed to compare the costs and outcomes of a QIV vaccination program compared with TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea. Influenza-related parameters (probabilities, health resource use, and costs) were derived from an analysis of the National Health Insurance System claims database between 2010 and 2013 under a broad and narrow set of International Classification of Diseases, Tenth Revision (ICD-10) codes used to identify influenza. Other inputs were extracted from published literature. Incremental cost-effectiveness ratios (2016 South Korean Won [KRW] per quality-adjusted life-year [QALY] gained) were estimated using a 'limited' societal perspective as per the Korean pharmacoeconomic guidelines. QALYs lost due to premature mortality were discounted at 5% annually.

RESULTS

For both age groups combined, under the narrow definition of influenza, QIV is expected to prevent nearly 16,000 (2923 in children and 13,011 in older adults) medically attended influenza cases, nearly 8000 (672 in children, 7048 in older adults) cases of complications, and over 230 (0 in children, 238 in older adults) deaths annually compared with TIV. The impact of using QIV versus TIV in this setting translates into savings of KRW 24 billion (KRW 0.6 billion in children, KRW 23.4 billion in older adults) in annual medical costs, and over 2100 (18 in children, 2084 in older adults) QALYs. Under the broad definition, the corresponding results are over 190,000 (50,697 in children, 140,644 in older adults) influenza cases, over 37,000 (12,623 in children, 24,526 in older adults) complications, 270 deaths (0 in children, 270 in older adults), KRW 94.22 billion (KRW 16 billion in children, KRW 78.2 billion in older adults), and over 3500 QALYs saved (316 in children, 3260 in older adults).

CONCLUSION

The use of QIV over TIV was estimated to not be cost effective in children 6-59 months of age, but cost saving in older adults, using the narrow definition of influenza; however, QIV use was cost saving in both age groups using the broad definition. QIV is expected to yield more benefits in older adults ≥ 65 years of age than in children aged 6-59 months due to higher influenza-related mortality and costs among the older adults. Further analyses considering the indirect effects of influenza vaccination in children are required.

Smartphone app uses loyalty point incentives and push notifications to encourage influenza vaccine uptake

PURPOSE

Carrot Rewards is a free, incentive-based, smartphone health app available in participating provinces in Canada. One feature of Carrot was designed to incentivize influenza vaccine education messages and encourage vaccine uptake for users in the province of British Columbia. This study aimed to evaluate the uptake of the Carrot Flu Campaign educational quiz and to determine if mobile "push" notifications, plus loyalty point incentives, resulted in users visiting a sponsored pharmacy to discuss and receive the influenza vaccine.

METHODS

The Carrot Flu Campaign delivered an in-app quiz, educating users on the importance of the influenza vaccine. Push notifications were then sent to users when they came within 200 m of a sponsored pharmacy. Those who visited the pharmacy collected bonus points and completed a follow up quiz tracking influenza vaccine behaviour. A sub-sample of users completed the Flu Campaign between their baseline and follow up Health Risk Assessment (HRA), a survey which asked about influenza vaccine uptake behaviour. Descriptive statistics were summarized.

RESULTS

A total of 38.1% (30,538/80,228) registered Carrot users completed the Flu Campaign quiz. Of those in participating cities (n = 21,469), 41% clicked on the map to show the nearest sponsored pharmacy and 78% enabled their smartphone's "locations" feature, allowing them to receive the push notifications. A small number of users spoke to a pharmacist (n = 96) and less than half reported receiving the influenza vaccine (38/96; 39.6%). From the HRA sub-sample (n = 3693), approximately 5% more users reported receiving the influenza vaccine during the 2017 influenza season compared to the previous year.

CONCLUSIONS

Carrot Rewards used a novel delivery method to educate the general population and showed geolocation could be used to facilitate influenza vaccine uptake. Future iterations could tailor content to target those most at risk and should consider more robust evaluation methods to determine the app's effectiveness.

Heterogeneous estimates of influenza virus types A and B in the elderly: Results of a meta-regression analysis

Influenza has many age‐dependent characteristics. A previous systematic review of randomized controlled trials showed that the detection rate of influenza B was higher in children than in non‐elderly adults. However, no comprehensive reviews have targeted the elderly, who carry the main burden of disease. We aimed to quantify the relative detection rates of virus types A and B among the elderly, to identify factors affecting these proportions, and to compare type distribution among seniors and younger age‐classes. A comprehensive literature search was conducted to identify multiseason studies reporting A and B virus type distributions in the elderly. A random‐effects meta‐analysis was planned to quantify the prevalence of type B among elderly subjects with laboratory‐confirmed influenza. Meta‐regression was then applied to explain the sources of heterogeneity. Across 27 estimates identified, the type B detection rate among seniors varied from 5% to 37%. Meta‐analysis was not feasible owing to high heterogeneity (I² = 98.5%). Meta‐regression analysis showed that study characteristics, such as number of seasons included, hemisphere, and setting, could have contributed to the heterogeneity observed. The final adjusted model showed that studies that included both outpatients and inpatients reported a significantly (P = .024) lower proportion than those involving outpatients only. The detection rate of type B among the elderly was generally lower than in children/adolescents, but not non‐elderly adults. Influenza virus type B has a relatively low detection rate in older adults, especially in settings covering both inpatients and outpatients. Public health implications are discussed.