Typical Influenza Season Research Articles

Antibody titres elicited by the 2018 seasonal inactivated influenza vaccine decline by 3months post-vaccination but persist for at least 6months.

In Australia, seasonal inactivated influenza vaccine is typically offered in April. However, the onset, peak and end of a typical influenza season vary, and optimal timing for vaccination remains unclear. Here, we investigated vaccine-induced antibody response kinetics over 6 months in different age groups. We conducted a prospective serosurvey among 71 adults aged 18-50 years, 15 community-dwelling ('healthy') and 16 aged-care facility resident ('frail') older adults aged ≥65 years who received the 2018 southern hemisphere vaccines. Sera were collected at baseline, and 1, 2, 4, and 6 months post-vaccination. Antibody titres were measured by haemagglutination inhibition or microneutralisation assays. Geometric mean titres were estimated using random effects regression modelling and superimposed on 2014-2018 influenza season epidemic curves. Antibody titres peaked 1.2-1.3months post-vaccination for all viruses, declined by 3months post-vaccination but, notably, persisted above baseline after 6months in all age groups by 1.3- to 1.5-fold against A(H1N1)pdm09, 1.7- to 2-fold against A(H3N2), 1.7- to 2.1-fold against B/Yamagata and 1.8-fold against B/Victoria. Antibody kinetics were similar among different age groups. Antibody responses were poor against cell-culture grown compared to egg-grown viruses. These results suggest subtype-specific antibody-mediated protection persists for at least 6months, which corresponds to the duration of a typical influenza season.

Self-medication and ILI etiologies among individuals presenting at pharmacies with influenza-like illness: Guatemala City, 2018 influenza season

ObjectivesWe aimed to characterize the proportion of clients presenting to community pharmacies with influenza-like illness (ILI) and the severity of their illness; the proportion with detectable influenza A, influenza B, and other pathogens (i.e., parainfluenza I, II, and III, adenovirus, respiratory syncytial virus, human metapneumovirus); and to describe their self-medication practices.MethodsA cross-sectional study was conducted in six pharmacies in Guatemala City. Study personnel collected nasopharyngeal and oropharyngeal swabs from participants who met the ILI case definition and who were self-medicating for the current episode. Participants were tested for influenza A and B and other pathogens using real-time RT-PCR. Participants’ ILI-associated self-medication practices were documented using a questionnaire.ResultsOf all patients entering the pharmacy during peak hours who responded to a screening survey (n = 18,016) 6% (n = 1029) self-reported ILI symptoms, of which 45% (n = 470/1029) met the study case definition of ILI. Thirty-one percent (148/470) met inclusion criteria, of which 87% (130/148) accepted participation and were enrolled in the study. Among 130 participants, nearly half tested positive for viral infection (n = 55, 42.3%) and belonged to groups at low risk for complications from influenza. The prevalence of influenza A was 29% (n = 35). Thirteen percent of the study population (n = 17) tested positive for a respiratory virus other than influenza. Sixty-four percent of participants (n = 83) reported interest in receiving influenza vaccination if it were to become available in the pharmacy. Medications purchased included symptom-relieving multi-ingredient cold medications (n = 43/100, 43%), nonsteroidal anti-inflammatory drugs (n = 23, 23%), and antibiotics (n = 16, 16%). Antibiotic use was essentially equal among antibiotic users regardless of viral status. The broad-spectrum antibiotics ceftriaxone and azithromycin were the most common antibiotics purchased.ConclusionsDuring a typical influenza season, a relatively low proportion of all pharmacy visitors were experiencing influenza symptoms. A high proportion of clients presenting to pharmacies with ILI tested positive for a respiratory virus. Programs that guide appropriate use of antibiotics in this population are needed and become increasingly important during pandemics caused by respiratory viral pathogens.

Respiratory virus detection during the COVID‐19 pandemic in Queensland, Australia

ObjectiveTo determine if non‐pharmaceutical interventions (NPIs) impacted on respiratory virus detections in Queensland, Australia, during the COVID‐19 pandemic year of 2020. MethodsWe analysed weekly counts of influenza, human metapneumovirus, parainfluenza, respiratory syncytial virus, rhinovirus, and adenovirus available from a Queensland laboratory network for the year 2020. These were compared with averaged counts from 2015 to 2019. ResultsOverall, 686,199 tests were performed. The timing of NPI implementation was associated with a sharp and sustained decline in influenza, where during the typical annual influenza season (weeks 23–40) no cases were detected from 163,296 tests compared with an average of 26.1% (11,844/45,396) of tests positive in 2015–2019. Similar results were observed for human metapneumovirus and parainfluenza. Respiratory syncytial virus detections also declined but increased in weeks 48–52 (5.6%; 562/10,078) to exceed the 2015–2019 average (2.9%; 150/5,018). Rhinovirus detections increased after schools reopened, peaking in weeks 23–27 (57.4%; 36,228/63,115), exceeding the 2017–2019 detections during that period (21.9%; 8,365/38,072). ConclusionsNPIs implemented to control COVID‐19 were associated with altered frequency and proportions of respiratory virus detections. Implications for public healthNPIs derived from influenza pandemic plans were associated with profound decreases in influenza detections during 2020.

A Note on Excess Mortality Attributable to COVID-19 in the United States.

Annual influenza outbreaks constitute a major public health concern in the United States. But this health burden appears dwarfed by the impact of COVID-19. Our aim is to quantify the excess mortality attributable to COVID-19, compared to previous influenza seasons. We retrospectively compare weekly mortality figures attributable to influenza and pneumonia in the United States from 2013 to 2019 with corresponding figures attributable to influenza, pneumonia, and COVID-19 from 2019 to 2021. We utilize a difference in differences regression methodology to estimate excess mortality observed in 2019-21 compared to 2013-2019. Mortality patterns attributable to influenza, pneumonia, and COVID-19 differ significantly from the 2013-19 experience. Notably, distinct, aperiodic mortality waves occur in the 2019-2021 window, and mortality is well in excess of what is observed in typical influenza seasons. The COVID-19 pandemic has led to considerable excess mortality in the United States, and has strained public health resources. One might expect that the mortality waves observed during the pandemic will be damped by increasing levels of vaccination, and prior infections.

The Case for Mandating COVID-19 Vaccines for Health Care Workers.

The Case for Mandating COVID-19 Vaccines for Health Care Workers.

Public Health and Economic Benefits of Influenza Vaccination of the Population Aged 50 to 59 Years without Risk Factors for Influenza Complications in Mexico: A Cross-Sectional Epidemiological Study.

The Mexican influenza vaccination program does not include a recommendation for people aged 50–59 years without risk factors for influenza complications, and there are limited data regarding the cost-effectiveness of vaccinating this population. To explore the clinical and economic effects of including this population in the vaccination schedule, we performed a cross-sectional epidemiological study using records (2009–2018) from Mexico’s Influenza Surveillance System (SISVEFLU), death records (2010–2015) from the National Mortality Epidemiological and Statistical System, and discharge and hospitalization records (2010–2015) from the Automated Hospital Discharge System databases. A 1-year decision-analytic model was used to assess cost-effectiveness through a decision-tree based on data from SISVEFLU. The primary outcome was influenza cases avoided; with associated influenza-related events as secondary outcomes. Including the population aged 50–59 years without risk factors in Mexico’s influenza immunization program would have resulted in 199,500 fewer cases; 67,008 fewer outpatient consultations; 33,024 fewer emergency room consultations; 33,091 fewer hospitalizations; 12 fewer deaths. These reductions equate to a substantial public health benefit as well as an economic benefit; yielding net savings of 49.8 million US dollars over a typical influenza season. Expansion of the current Mexican vaccination schedule to include these people would be a cost-saving and dominant strategy.

Children's Hospital ICU Resource Allocation in an Adult Pandemic.

* Abbreviation: COVID-19 — : coronavirus disease 2019 Imagine the following situation: A 25-year-old is intubated in the emergency department for coronavirus disease 2019 (COVID-19)–related acute respiratory distress syndrome. The adult ICU is full. The nearby PICU has many available beds and staff. The pediatric intensivist and their administrators must decide how to respond. Do ethical considerations permit, require, or forbid extending PICU care to this adult patient? Two features of the COVID-19 pandemic make situations like this increasingly likely. First, there is significant variation in disease incidence. Adults are at much higher risk of serious COVID-19–related illness requiring ICU care than are children.1,2 Children generally have had fewer infections and milder disease.3,4 Second, there is significant variation in available capacity. According to the Society of Critical Care Medicine, there are only 68 558 adult ICU beds, 5137 PICU beds, 22 901 NICU beds, 25 157 step-down beds, and 1183 burn beds in the United States today.5 In a moderate or severe outbreak, with tens of thousands of adults requiring ICU care,1 the need will quickly outstrip available resources.6 Children’s hospitals, by contrast, likely will have surplus capacity. We are at the end of the typical influenza and respiratory syncytial virus seasons. We have canceled nearly all elective surgery nationwide, easing demand for postoperative care in the PICU. This has left … Address correspondence to Ian D. Wolfe, PhD, RN, CCRN, Children’s Mercy Bioethics Center, 2401 Gillham Rd, Kansas City, MO 64108. E-mail: wolfe370{at}umn.edu

Distinguishing the novel coronavirus from influenza

Distinguishing the novel coronavirus from influenza

Patterns of seasonal and pandemic influenza-associated health care and mortality in Ontario, Canada

BackgroundMathematical and statistical models are used to project the future time course of infectious disease epidemics and the expected future burden on health care systems and economies. Influenza is a particularly important disease in this context because it causes annual epidemics and occasional pandemics. In order to forecast health care utilization during epidemics—and the effects of hospitalizations and deaths on the contact network and, in turn, on transmission dynamics—modellers must make assumptions about the lengths of time between infection, visiting a physician, being admitted to hospital, leaving hospital, and death. More reliable forecasts could be be made if the distributions of times between these types of events (“delay distributions”) were known.MethodsWe estimated delay distributions in the province of Ontario, Canada, between 2006 and 2010. To do so, we used encrypted health insurance numbers to link 1.34 billion health care billing records to 4.27 million hospital inpatient stays. Because the four year period we studied included three typical influenza seasons and the 2009 influenza pandemic, we were able to compare the delay distributions in non-pandemic and pandemic settings. We also estimated conditional probabilities such as the probability of hospitalization within the year if diagnosed with influenza.ResultsIn non-pandemic [pandemic] years, delay distribution medians (inter-quartile ranges) were: Service to Admission 6.3 days (0.1–17.6 days) [2.4 days (-0.3–13.6 days)], Admission to Discharge 3 days (1.4–5.9 days) [2.6 days (1.2–5.1 days)], Admission to Death 5.3 days (2.1–11 days) [6 days (2.6–13.1 days)]. (Service date is defined as the date, within the year, of the first health care billing that included a diagnostic code for influenza-like-illness.) Among individuals diagnosed with either pneumonia or influenza in a given year, 19% [16%] were hospitalized within the year and 3% [2%] died in hospital. Among all individuals who were hospitalized, 10% [12%] were diagnosed with pneumonia or influenza during the year and 5% [5%] died in hospital.ConclusionOur empirical delay distributions and conditional probabilities should help facilitate more accurate forecasts in the future, including improved predictions of hospital bed demands during influenza outbreaks, and the expected effects of hospitalizations on epidemic dynamics.

Effects of Sequential Influenza A(H1N1)pdm09 Vaccination on Antibody Waning.

Antibody waning following influenza vaccination has been repeatedly evaluated, but waning has rarely been studied in the context of longitudinal vaccination history. We developed a Bayesian hierarchical model to assess the effects of sequential influenza A(H1N1)pdm09 vaccination on hemagglutination inhibition antibody boosting and waning in a longitudinal cohort of older children and adults from 2011 to 2016, a period during which the A(H1N1)pdm09 vaccine strain did not change. Antibody measurements from 2057 serum specimens longitudinally collected from 388 individuals were included. Average postvaccination antibody titers were similar across successive vaccinations, but the rate of antibody waning increased with each vaccination. The antibody half-life was estimated to decrease from 32 months (95% credible interval [CrI], 22-61 months) following first vaccination to 9 months (95% CrI, 7-15 months) following a seventh vaccination. Although the rate of antibody waning increased with successive vaccination, the estimated antibody half-life was longer than a typical influenza season even among the most highly vaccinated. This supports current recommendations for vaccination at the earliest opportunity. Patterns of boosting and waning might be different with the influenza A(H3N2) subtype, which evolves more rapidly and has been most associated with reduced effectiveness following repeat vaccination.

Incorporating media data into a model of infectious disease transmission.

Understanding the effect of media on disease spread can help improve epidemic forecasting and uncover preventive measures to slow the spread of disease. Most previously introduced models have approximated media effect through disease incidence, making media influence dependent on the size of epidemic. We propose an alternative approach, which relies on real data about disease coverage in the news, allowing us to model low incidence/high interest diseases, such as SARS, Ebola or H1N1. We introduce a network-based model, in which disease is transmitted through local interactions between individuals and the probability of transmission is affected by media coverage. We assume that media attention increases self-protection (e.g. hand washing and compliance with social distancing), which, in turn, decreases disease model. We apply the model to the case of H1N1 transmission in Mexico City in 2009 and show how media influence—measured by the time series of the weekly count of news articles published on the outbreak—helps to explain the observed transmission dynamics. We show that incorporating the media attention based on the observed media coverage of the outbreak better estimates the disease dynamics from what would be predicted by using media function that approximate the media impact using the number of cases and rate of spread. Finally, we apply the model to a typical influenza season in Washington, DC and estimate how the transmission pattern would have changed given different levels of media coverage.

Severe Influenza in 33 US Hospitals, 2013-2014: Complications and Risk Factors for Death in 507 Patients.

Influenza A (H1N1) pdm09 became the predominant circulating strain in the United States during the 2013-2014 influenza season. Little is known about the epidemiology of severe influenza during this season. A retrospective cohort study of severely ill patients with influenza infection in intensive care units in 33 US hospitals from September 1, 2013, through April 1, 2014, was conducted to determine risk factors for mortality present on intensive care unit admission and to describe patient characteristics, spectrum of disease, management, and outcomes. A total of 444 adults and 63 children were admitted to an intensive care unit in a study hospital; 93 adults (20.9%) and 4 children (6.3%) died. By logistic regression analysis, the following factors were significantly associated with mortality among adult patients: older age (>65 years, odds ratio, 3.1 [95% CI, 1.4-6.9], P=.006 and 50-64 years, 2.5 [1.3-4.9], P=.007; reference age 18-49 years), male sex (1.9 [1.1-3.3], P=.031), history of malignant tumor with chemotherapy administered within the prior 6 months (12.1 [3.9-37.0], P<.001), and a higher Sequential Organ Failure Assessment score (for each increase by 1 in score, 1.3 [1.2-1.4], P<.001). Risk factors for death among US patients with severe influenza during the 2013-2014 season, when influenza A (H1N1) pdm09 was the predominant circulating strain type, shifted in the first postpandemic season in which it predominated toward those of a more typical epidemic influenza season.

An Assessment of the Expected Cost-Effectiveness of Quadrivalent Influenza Vaccines in Ontario, Canada Using a Static Model.

Ontario, Canada, immunizes against influenza using a trivalent inactivated influenza vaccine (IIV3) under a Universal Influenza Immunization Program (UIIP). The UIIP offers IIV3 free-of-charge to all Ontarians over 6 months of age. A newly approved quadrivalent inactivated influenza vaccine (IIV4) offers wider protection against influenza B disease. We explored the expected cost-utility and budget impact of replacing IIV3 with IIV4, within the context of Ontario’s UIIP, using a probabilistic and static cost-utility model. Wherever possible, epidemiological and cost data were obtained from Ontario sources. Canadian or U.S. sources were used when Ontario data were not available. Vaccine efficacy for IIV3 was obtained from the literature. IIV4 efficacy was derived from meta-analysis of strain-specific vaccine efficacy. Conservatively, herd protection was not considered. In the base case, we used IIV3 and IIV4 prices of $5.5/dose and $7/dose, respectively. We conducted a sensitivity analysis on the price of IIV4, as well as standard univariate and multivariate statistical uncertainty analyses. Over a typical influenza season, relative to IIV3, IIV4 is expected to avert an additional 2,516 influenza cases, 1,683 influenza-associated medical visits, 27 influenza-associated hospitalizations, and 5 influenza-associated deaths. From a societal perspective, IIV4 would generate 76 more Quality Adjusted Life Years (QALYs) and a net societal budget impact of $4,784,112. The incremental cost effectiveness ratio for this comparison was $63,773/QALY. IIV4 remains cost-effective up to a 53% price premium over IIV3. A probabilistic sensitivity analysis showed that IIV4 was cost-effective with a probability of 65% for a threshold of $100,000/QALY gained. IIV4 is expected to achieve reductions in influenza-related morbidity and mortality compared to IIV3. Despite not accounting for herd protection, IIV4 is still expected to be a cost-effective alternative to IIV3 up to a price premium of 53%. Our conclusions were robust in the face of sensitivity analyses.

The health and economic impact of vaccination with 7-valent pneumococcal vaccine (PCV7) during an annual influenza epidemic and influenza pandemic in China.

BackgroundChina has experienced several severe outbreaks of influenza over the past century: 1918, 1957, 1968, and 2009. Influenza itself can be deadly; however, the increase in mortality during an influenza outbreak is also attributable to secondary bacterial infections, specifically pneumococcal disease. Given the history of pandemic outbreaks and the associated morbidity and mortality, we investigated the cost-effectiveness of a PCV7 vaccination program in China from the context of typical and pandemic influenza seasons.MethodsA decision-analytic model was employed to evaluate the impact of a 7-valent pneumococcal vaccine (PCV7) infant vaccination program on the incidence, mortality, and cost associated with pneumococcal disease during a typical influenza season (15 % flu incidence) and influenza pandemic (30 % flu incidence) in China. The model incorporated Chinese data where available and included both direct and indirect (herd) effects on the unvaccinated population, assuming a point in time following the initial introduction of the vaccine where the impact of the indirect effects has reached a steady state, approximately seven years following the implementation of the vaccine program. Pneumococcal disease incidence, mortality, and costs were evaluated over a one year time horizon. Healthcare costs were calculated using a payer perspective and included vaccination program costs and direct medical expenditures from pneumococcal disease.ResultsThe model predicted that routine PCV7 vaccination of infants in China would prevent 5,053,453 cases of pneumococcal disease and 76,714 deaths in a single year during a normal influenza season.The estimated incremental-cost-effectiveness ratios were ¥12,281 (US$1,900) per life-year saved and ¥13,737 (US$2,125) per quality-adjusted-life-year gained. During an influenza pandemic, the model estimated that routine vaccination with PCV7 would prevent 8,469,506 cases of pneumococcal disease and 707,526 deaths, and would be cost-saving.ConclusionsRoutine vaccination with PCV7 in China would be a cost-effective strategy at limiting the negative impact of influenza during a typical influenza season. During an influenza pandemic, the benefit of PCV7 in preventing excess pneumococcal morbidity and mortality renders a PCV7 vaccination program cost-saving.

Cost effectiveness analysis of Year 2 of an elementary school-located influenza vaccination program-Results from a randomized controlled trial.

BackgroundSchool-located vaccination against influenza (SLV-I) has the potential to improve current suboptimal influenza immunization coverage for U.S. school-aged children. However, little is known about SLV-I’s cost-effectiveness. The objective of this study is to establish the cost-effectiveness of SLV-I based on a two-year community-based randomized controlled trial (Year 1: 2009–2010 vaccination season, an unusual H1N1 pandemic influenza season, and Year 2: 2010–2011, a more typical influenza season).MethodsWe performed a cost-effectiveness analysis on a two-year randomized controlled trial of a Western New York SLV-I program. SLV-I clinics were offered in 21 intervention elementary schools (Year 1 n = 9,027; Year 2 n = 9,145 children) with standard-of-care (no SLV-I) in control schools (Year 1 n = 4,534 (10 schools); Year 2 n = 4,796 children (11 schools)). We estimated the cost-per-vaccinated child, by dividing the incremental cost of the intervention by the incremental effectiveness (i.e., the number of additionally vaccinated students in intervention schools compared to control schools).ResultsIn Years 1 and 2, respectively, the effectiveness measure (proportion of children vaccinated) was 11.2 and 12.0 percentage points higher in intervention (40.7 % and 40.4 %) than control schools. In year 2, the cost-per-vaccinated child excluding vaccine purchase ($59.88 in 2010 US $) consisted of three component costs: (A) the school costs ($8.25); (B) the project coordination costs ($32.33); and (C) the vendor costs excluding vaccine purchase ($16.68), summed through Monte Carlo simulation. Compared to Year 1, the two component costs (A) and (C) decreased, while the component cost (B) increased in Year 2. The cost-per-vaccinated child, excluding vaccine purchase, was $59.73 (Year 1) and $59.88 (Year 2, statistically indistinguishable from Year 1), higher than the published cost of providing influenza vaccination in medical practices ($39.54). However, taking indirect costs (e.g., averted parental costs to visit medical practices) into account, vaccination was less costly in SLV-I ($23.96 in Year 1, $24.07 in Year 2) than in medical practices.ConclusionsOur two-year trial’s findings reinforced the evidence to support SLV-I as a potentially favorable system to increase childhood influenza vaccination rates in a cost-efficient way. Increased efficiencies in SLV-I are needed for a sustainable and scalable SLV-I program.

Epidemiological and viral genome characteristics of the first human H7N9 influenza infection in Guangdong Province, China.

The first H7N9 human case in south of China was confirmed in Guangdong Province on August 2013, outside of the typical influenza season. For investigating the H7N9 virus source and transmission in the local community, we analyze the epidemiology and genome features of the virus isolated from the first human infection detected in Guangdong Province. The data including medical records, exposure history and time line of events for the H7N9 patient and close contacts was collected. Variation and genetic signatures of H7N9 virus in Guangdong was analyzed using ClustalW algorithm and comparison with mutations associated with changes in biological characteristics of the virus. The female patient had a history of poultry exposure, and she was transferred from a local primary hospital to an intensive care unit (ICU) upon deterioration. No additional cases were reported. Similar to previous infections with avian influenza A (H7N9) virus, the patient presented with both upper and lower respiratory tract symptoms. Respiratory failure progressed quickly, and the patient recovered 4 weeks after the onset of symptoms. Genome analysis of the virus indicated that the predicted antigen city and internal genes of the virus are similar to previously reported H7N9 viruses. The isolated virus is susceptible to neuraminidase (NA) inhibitors but resistant to adamantine. Although this virus contains some unique mutations that were only detected in avian or environment-origin avian influenza A (H7N9) viruses, it is still quite similar to other human H7N9 isolates. The epidemiological features and genome of the first H7N9 virus in Guangdong Province are similar to other human H7N9 infections. This virus may have existed in the environment and live poultry locally; therefore, it is important to be alert of the risk of H7N9 re-emergence in China, including emergence outside the typical influenza season.

PIN57 - The Health And Economic Impact Of Vaccination With 7-Valent Pneumococcal Vaccine (PCV7) During An Annual Influenza Epidemic And Influenza Pandemic In China

Background: China has experienced several severe outbreaks of influenza over the past century: 1918, 1957, 1968, and 2009. Influenza itself can be deadly; however, the increase in mortality during an influenza outbreak is also attributable to secondary bacterial infections, specifically pneumococcal disease. Given the history of pandemic outbreaks and the associated morbidity and mortality, we investigated the cost-effectiveness of a PCV7 vaccination program in China from the context of typical and pandemic influenza seasons. Methods: A decision-analytic model was employed to evaluate the impact of a 7-valent pneumococcal vaccine (PCV7) infant vaccination program on the incidence, mortality, and cost associated with pneumococcal disease during a typical influenza season (15 % flu incidence) and influenza pandemic (30 % flu incidence) in China. The model incorporated Chinese data where available and included both direct and indirect (herd) effects on the unvaccinated population, assuming a point in time following the initial introduction of the vaccine where the impact of the indirect effects has reached a steady state, approximately seven years following the implementation of the vaccine program. Pneumococcal disease incidence, mortality, and costs were evaluated over a one year time horizon. Healthcare costs were calculated using a payer perspective and included vaccination program costs and direct medical expenditures from pneumococcal disease. Results: The model predicted that routine PCV7 vaccination of infants in China would prevent 5,053,453 cases of pneumococcal disease and 76,714 deaths in a single year during a normal influenza season.The estimated incremental-cost-effectiveness ratios were ¥12,281 (US$1,900) per life-year saved and ¥13,737 (US$2,125) per quality-adjusted-life-year gained. During an influenza pandemic, the model estimated that routine vaccination with PCV7 would prevent 8,469,506 cases of pneumococcal disease and 707,526 deaths, and would be cost-saving. Conclusions: Routine vaccination with PCV7 in China would be a cost-effective strategy at limiting the negative impact of influenza during a typical influenza season. During an influenza pandemic, the benefit of PCV7 in preventing excess pneumococcal morbidity and mortality renders a PCV7 vaccination program cost-saving.

Mortality burden of the A/H1N1 pandemic in Mexico: a comparison of deaths and years of life lost to seasonal influenza.

The mortality burden of the 2009 A/H1N1 influenza pandemic remains controversial, in part because of delays in reporting of vital statistics that are traditionally used to measure influenza-related excess mortality. Here, we compare excess mortality rates and years of life lost (YLL) for pandemic and seasonal influenza in Mexico and evaluate laboratory-confirmed death reports. Monthly age- and cause-specific death rates from January 2000 through April 2010 and population-based surveillance of influenza virus activity were used to estimate excess mortality and YLL in Mexico. Age-stratified laboratory-confirmed A/H1N1 death reports were obtained from an active surveillance system covering 40% of the population. The A/H1N1 pandemic was associated with 11.1 excess all-cause deaths per 100,000 population and 445,000 YLL during the 3 waves of virus activity in Mexico, April-December 2009. The pandemic mortality burden was 0.6-2.6 times that of a typical influenza season and lower than that of the severe 2003-2004 influenza epidemic. Individuals aged 5-19 and 20-59 years were disproportionately affected relative to their experience with seasonal influenza. Laboratory-confirmed deaths captured 1 of 7 pandemic excess deaths overall but only 1 of 41 deaths in persons >60 years of age in 2009. A recrudescence of excess mortality was observed in older persons during winter 2010, in a period when influenza and respiratory syncytial virus cocirculated. Mexico experienced higher 2009 A/H1N1 pandemic mortality burden than other countries for which estimates are available. Further analyses of detailed vital statistics are required to assess geographical variation in the mortality patterns of this pandemic.

Cost-effectiveness of influenza vaccination of older adults in the ED setting

ObjectivesAdults older than 50 years are at greater risk for death and severe disability from influenza. Persons in this age group, however, are frequently not vaccinated, despite extensive efforts by physicians to provide this preventive measure in primary care settings. We performed this study to determine if influenza vaccination of older adults in the emergency department (ED) may be cost-effective. MethodsUsing a probabilistic decision model with quasi-Markov modeling of a typical influenza season, we calculated costs and health outcomes for a hypothetical cohort of patients using parameters from the literature. Three ED-based intervention strategies were compared: (1) no vaccination offered, (2) vaccination offered to patients older than 65 years (limited strategy), and (3) vaccination offered to all patients who are 50 years and older (inclusive strategy). Outcomes were measured as costs, lives saved, and incremental costs per life saved. We performed deterministic and probabilistic sensitivity analyses. ResultsVaccination of patients 50 years of age and older results in an incremental cost of $34 610 per life saved when compared with the no-vaccination strategy. Limiting vaccination to only those older than 65 years results in an incremental cost of $13 084 per life saved. Results were sensitive to changes in vaccine cost but were insensitive to changes in other model parameters. ConclusionsVaccination of older adults against influenza in the ED setting is cost-effective, especially for those older than 65 years. Emergency departments may be an important setting for providing influenza vaccination to adults who may otherwise have remained unvaccinated.

Transmission Characteristics of the 2009 H1N1 Influenza Pandemic: Comparison of 8 Southern Hemisphere Countries

While in Northern hemisphere countries, the pandemic H1N1 virus (H1N1pdm) was introduced outside of the typical influenza season, Southern hemisphere countries experienced a single wave of transmission during their 2009 winter season. This provides a unique opportunity to compare the spread of a single virus in different countries and study the factors influencing its transmission. Here, we estimate and compare transmission characteristics of H1N1pdm for eight Southern hemisphere countries/states: Argentina, Australia, Bolivia, Brazil, Chile, New Zealand, South Africa and Victoria (Australia). Weekly incidence of cases and age-distribution of cumulative cases were extracted from public reports of countries' surveillance systems. Estimates of the reproduction numbers, R 0, empirically derived from the country-epidemics' early exponential phase, were positively associated with the proportion of children in the populations (p = 0.004). To explore the role of demography in explaining differences in transmission intensity, we then fitted a dynamic age-structured model of influenza transmission to available incidence data for each country independently, and for all the countries simultaneously. Posterior median estimates of R 0 ranged 1.2–1.8 for the country-specific fits, and 1.29–1.47 for the global fits. Corresponding estimates for overall attack-rate were in the range 20–50%. All model fits indicated a significant decrease in susceptibility to infection with age. These results confirm the transmissibility of the 2009 H1N1 pandemic virus was relatively low compared with past pandemics. The pattern of age-dependent susceptibility found confirms that older populations had substantial – though partial - pre-existing immunity, presumably due to exposure to heterologous influenza strains. Our analysis indicates that between-country-differences in transmission were at least partly due to differences in population demography.