Cost-effectiveness of pembrolizumab for the first-line treatment of recurrent or metastatic head and neck squamous cell carcinoma in the United States.

AIMS: Pembrolizumab, as monotherapy in first-line recurrent or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) with a combined positive score (CPS) ≥1 and in combination with platinum and 5-fluorouracil (5-FU) in the overall R/M HNSCC population, received US FDA approval based on the KEYNOTE-048 trial. Using public drug prices, from a US payer perspective, we evaluated the cost-effectiveness of each pembrolizumab regimen vs. cetuximab + platinum+5-FU (EXTREME regimen, trial comparator), cisplatin + docetaxel + cetuximab (TPEx regimen), cisplatin + paclitaxel, and platinum+5-FU. METHODS: A three-state partitioned-survival model was used to project costs and outcomes over 20 years with 3% annual discounting. Progression-free and overall survival were modeled using long-term extrapolation of KEYNOTE-048 data and, for alternative comparators, data from a network meta-analysis was used. Time-on-treatment was derived from KEYNOTE-048 or approximated using network meta-analysis progression-free survival estimates. Costs included first-line and subsequent treatments, disease management, adverse events, and terminal care costs. Utilities were derived from the KEYNOTE-048 Euro-QoL five-dimension data and using a US algorithm. RESULTS: In the CPS ≥1 R/M HNSCC population, pembrolizumab monotherapy was dominant vs. EXTREME and TPEx regimens, and cost-effective (at $100,000/QALY threshold) vs. platinum+5-FU ($86,827/QALY) and cisplatin + paclitaxel ($81,473/QALY). Pembrolizumab combination therapy in the overall R/M HNSCC population was dominant vs. TPEx regimen, and cost-effective vs. EXTREME regimen ($1769/QALY), platinum+5-FU ($81,989/QALY), and cisplatin + paclitaxel ($89,505/QALY). Sensitivity analyses showed a high cost-effectiveness probability for pembrolizumab at the $100,000/QALY threshold. CONCLUSIONS: First-line pembrolizumab monotherapy in patients with CPS ≥1, and pembrolizumab combination therapy in the overall R/M HNSCC population is cost-effective from the perspective of the US payers.

Cost-Effectiveness of Pembrolizumab Regimens for the First-Line Treatment of Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma in Argentina.

INTRODUCTION: The phase III KEYNOTE-048 trial showed that the programmed death receptor 1 (PD-1) inhibitor pembrolizumab, in the combined positive score (CPS) ≥ 1 population and combined with platinum + 5-fluorouracil in the total population, improves survival over cetuximab + platinum + 5-fluorouracil in recurrent or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). We evaluated the cost-effectiveness of pembrolizumab as monotherapy in the CPS ≥ 1 population or combined with platinum + 5-fluorouracil in the total population versus cetuximab + platinum + 5-fluorouracil from the social security perspective in Argentina. METHODS: A partitioned survival model projected costs and outcomes over 20 years with 3% annual discounting. Health state occupancy was modeled using KEYNOTE-048 Kaplan-Meier curves until the final analysis data cutoff, followed by parametric extrapolations guided by statistical criteria. Costs for initial and subsequent treatments, disease and adverse events management, and terminal care were included (AR $74.00 = 1 USD). Time-on-treatment and EuroQol five-dimension scores were taken from KEYNOTE-048. Utilities were derived using an Argentina-specific algorithm. RESULTS: With pembrolizumab monotherapy, patients accrued 1.1040 additional life-years and 0.8768 additional quality-adjusted life-years (QALYs), for incremental cost-effectiveness ratios (ICERs) of AR $135,801/life-year and AR $170,985/QALY gained over cetuximab + platinum + 5-fluorouracil. Additional life-years and QALYs gained with pembrolizumab combination therapy versus cetuximab + platinum + 5-fluorouracil were 1.3296 and 1.0536, respectively (ICERs of AR $680,143/life-year and AR $858,306/QALY). Considering a threshold of AR $1,676,122/QALY gained, pembrolizumab monotherapy and combination therapy had an 88.0% and a 77.1% probability of being cost-effective, respectively. CONCLUSION: Pembrolizumab either as monotherapy or in combination with chemotherapy offers substantial survival gains for patients with R/M HNSCC at small additional costs, making it a cost-effective treatment versus cetuximab + platinum + 5-FU in Argentina.

Relapsed/refractory primary mediastinal large B-cell lymphoma: a structured review of epidemiology, treatment guidelines and real-world treatment practices.

Background: Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is an uncommon subtype of diffuse large B-cell lymphoma. Approximately 10-30% of patients experience refractory or relapsed PMBCL (rrPMBCL) after first-line therapy. Data and treatment guidelines for rrPMBCL are scarce, and management is based on clinical experience.Methods: Two structured literature reviews were undertaken to determine the incidence, prevalence, and mortality rates associated with rrPMBCL, and to identify clinical practice guidelines and real-world patterns of care.Results: Epidemiology studies included reported lymphomas (n = 1), non-Hodgkin lymphoma (n = 1), lymphoid neoplasm (n = 1), PMBCL (n = 6), and rrPMBCL (n = 1). Of 12 published treatment guidelines, only four provided recommendations for rrPMBCL. Sixteen studies provided data on real-world treatment patterns, but most were single-center studies with small patient numbers. Chemotherapy/immunochemotherapy, followed by high-dose treatment (HDT) and stem cell transplantation, was a mainstay of salvage therapy in most studies; real-world care generally followed treatment guidelines.Conclusions: Salvage chemotherapy (often with rituximab and radiotherapy), followed by HDT and stem cell transplantation, appears to be the standard real-world treatment for rrPMBCL. However, large prospective and retrospective studies are warranted to improve our knowledge of real-world treatment patterns.

The value of persistence in treatment with subcutaneous TNF-alpha inhibitors for ankylosing spondylitis.

OBJECTIVE: To estimate the impact of persistence on cost-effectiveness of subcutaneous tumor necrosis factor-α inhibitors (SC-TNFis) from healthcare and societal perspectives in a United Kingdom ankylosing spondylitis (AS) population using a recently published Markov cohort model. METHODS: A recently published cost-effectiveness model developed for a National Institute for health and Care Excellence appraisal was extended to fit the current study; in brief, it is a Markov cohort model where treatment responders continue from the trial period with maintenance SC-TNFi treatment, while non-responders transition to conventional care. Costs and effects were modeled for a hypothetical SC-TNFi with average efficacy and price. Model outcomes included quality-adjusted life-years (QALYs), total direct and indirect lifetime costs, and incremental cost-effectiveness ratios (ICERs). The cost-effectiveness of SC-TNFi persistence was estimated by decreasing the annual discontinuation probability in five percentage point increments from 25 to 5% per annum. RESULTS: From a health care perspective, the ICERs for the modeled discontinuation rates compared to the baseline annual discontinuation rate (25%) ranged between GBP 17,277 and GBP 18,161. From a societal perspective, increased discontinuation rates resulted in decreased total costs and higher QALYs; hence, lower discontinuation rates dominated higher discontinuation rates from a societal perspective. CONCLUSION: In conclusion, this study shows that, all else equal, higher SC-TNFi treatment persistence in AS is cost effective from a health care perspective and dominant from a societal perspective. Hence, all else equal, prescribing the SC-TNFi with the highest persistence may be considered a cost-effective strategy.

Cost-effectiveness of pembrolizumab versus brentuximab vedotin for patients with relapsed or refractory classical Hodgkin's lymphoma: a United States payer perspective.

AIMS: Patients with classical Hodgkin's lymphoma (cHL) who have relapsed after or are ineligible for autologous stem cell transplantation (ASCT) have limited treatment options and generally a poor prognosis. Pembrolizumab was recently approved in the US for the treatment of such patients having demonstrated clinical benefit and tolerability in relapsed/refractory cHL; however, the cost-effectiveness of pembrolizumab in this population is currently unknown. MATERIALS AND METHODS: A three-state Markov model (progression-free [PF], progressed disease, and death) was developed to assess the cost-effectiveness of pembrolizumab (200 mg) vs brentuximab vedotin (BV; 1.8 mg/kg) in patients with relapsed/refractory cHL after ASCT who have not received BV post-ASCT over a 20-year time horizon from a US payer perspective. PF survival was modeled using a naïve indirect treatment comparison of data from KEYNOTE-087 and the SG035-003 trial. Post-progression survival was modeled using data from published literature. Costs (drug acquisition and administration, disease management, subsequent treatment, and adverse events) and outcomes were discounted at an annual rate of 3.0%. Uncertainty surrounding cost-effectiveness was assessed via probabilistic, deterministic, and scenario analyses. RESULTS: In the base case, pembrolizumab was predicted to yield an additional 0.574 life-years (LYs) and 0.500 quality-adjusted life-years (QALYs) vs BV and cost savings of $63,278. Drug acquisition costs were the biggest driver of incremental costs between strategies. Pembrolizumab had a 99.6% probability of being cost-effective compared with BV at a willingness-to-pay threshold of $20,000/QALY and dominated BV in all scenarios tested. LIMITATIONS: The analysis was subject to potential bias due to the use of a naïve indirect treatment comparison and, given the current immaturity of OS in KEYNOTE-087, PPS was assumed equivalent across both treatments. CONCLUSION: Pembrolizumab is a cost-effective alternative to BV for patients with relapsed/refractory cHL after ASCT.

Cost-effectiveness of dog rabies vaccination programs in East Africa.

BACKGROUND: Dog rabies annually causes 24,000-70,000 deaths globally. We built a spreadsheet tool, RabiesEcon, to aid public health officials to estimate the cost-effectiveness of dog rabies vaccination programs in East Africa. METHODS: RabiesEcon uses a mathematical model of dog-dog and dog-human rabies transmission to estimate dog rabies cases averted, the cost per human rabies death averted and cost per year of life gained (YLG) due to dog vaccination programs (US 2015 dollars). We used an East African human population of 1 million (approximately 2/3 living in urban setting, 1/3 rural). We considered, using data from the literature, three vaccination options; no vaccination, annual vaccination of 50% of dogs and 20% of dogs vaccinated semi-annually. We assessed 2 transmission scenarios: low (1.2 dogs infected per infectious dog) and high (1.7 dogs infected). We also examined the impact of annually vaccinating 70% of all dogs (World Health Organization recommendation for dog rabies elimination). RESULTS: Without dog vaccination, over 10 years there would a total of be approximately 44,000-65,000 rabid dogs and 2,100-2,900 human deaths. Annually vaccinating 50% of dogs results in 10-year reductions of 97% and 75% in rabid dogs (low and high transmissions scenarios, respectively), approximately 2,000-1,600 human deaths averted, and an undiscounted cost-effectiveness of $451-$385 per life saved. Semi-annual vaccination of 20% of dogs results in in 10-year reductions of 94% and 78% in rabid dogs, and approximately 2,000-1,900 human deaths averted, and cost $404-$305 per life saved. In the low transmission scenario, vaccinating either 50% or 70% of dogs eliminated dog rabies. Results were most sensitive to dog birth rate and the initial rate of dog-to-dog transmission (Ro). CONCLUSIONS: Dog rabies vaccination programs can control, and potentially eliminate, dog rabies. The frequency and coverage of vaccination programs, along with the level of dog rabies transmission, can affect the cost-effectiveness of such programs. RabiesEcon can aid both the planning and assessment of dog rabies vaccination programs.

Cost-effectiveness Analysis of Golimumab in the Treatment of Non-Radiographic Axial Spondyloarthritis in Scotland.

INTRODUCTION: The aim of this study is to assess the cost-effectiveness of golimumab for the treatment of non-radiographic axial spondyloarthritis (nr-axSpA) vs. conventional therapy and other tumor necrosis factor inhibitors from the Scottish payer perspective. METHODS: A model comprising a short-term decision tree and a long-term Markov model was developed to compare cost-effectiveness (incremental costs per quality-adjusted life-year [QALY]) for patients in Scotland with nr-axSpA treated by conventional therapy, adalimumab, certolizumab pegol, etanercept, or golimumab for a lifetime period. A network meta-analysis (NMA) was conducted to identify clinical and safety data for treatments and synthesize the available evidence into relative treatment effects between comparators. The probability of patients achieving an Assessment of SpondyloArthritis International Society 20/40% response criteria (ASAS20/ASAS40) or a 50% improvement in Bath Ankylosing Spondylitis Disease Activity Index score (BASDAI50) at week 12 was obtained from the NMA for each of the comparators. Baseline health state utilities were based on the EQ-5D questionnaire collected in the golimumab GO-AHEAD study. The cost of treatment was calculated based on drug acquisition, drug administration, and initiation/monitoring costs. RESULTS: Golimumab resulted in an increase of 2.06 QALYs and additional cost of £39,770 compared with conventional therapy. Incremental cost per QALY gained was £19,280 for golimumab, which was lower than adalimumab (£19,737), etanercept (£20,089), and higher than certolizumab pegol (£18,710). Golimumab remained cost-effective throughout a range of sensitivity analyses where key assumptions were tested. CONCLUSIONS: From a Scottish perspective, golimumab was a cost-effective treatment for nr-axSpA compared with conventional therapy at a willingness-to-pay threshold of £30,000 per QALY. FUNDING: Merck & Co., Inc.

Cost-effectiveness of ceftolozane/tazobactam plus metronidazole versus piperacillin/tazobactam as initial empiric therapy for the treatment of complicated intra-abdominal infections based on pathogen distributions drawn from national surveillance data in the United States.

BACKGROUND: The prevalence of antimicrobial resistance among gram-negative pathogens in complicated intra-abdominal infections (cIAIs) has increased. In the absence of timely information on the infecting pathogens and their susceptibilities, local or regional epidemiology may guide initial empirical therapy and reduce treatment failure, length of stay and mortality. The objective of this study was to assess the cost-effectiveness of ceftolozane/tazobactam + metronidazole compared with piperacillin/tazobactam in the treatment of hospitalized US patients with cIAI at risk of infection with resistant pathogens. METHODS: We used a decision-analytic Monte Carlo simulation model to compare the costs and quality-adjusted life years (QALYs) of persons infected with nosocomial gram-negative cIAI treated empirically with either ceftolozane/tazobactam + metronidazole or piperacillin/tazobactam. Pathogen isolates were randomly drawn from the Program to Assess Ceftolozane/Tazobactam Susceptibility (PACTS) database, a surveillance database of non-duplicate bacterial isolates collected from patients with cIAIs in medical centers in the USA from 2011 to 2013. Susceptibility to initial therapy was based on the measured susceptibilities reported in the PACTS database determined using standard broth micro-dilution methods as described by the Clinical and Laboratory Standards Institute (CLSI). RESULTS: Our model results, with baseline resistance levels from the PACTS database, indicated that ceftolozane/tazobactam + metronidazole dominated piperacillin/tazobactam, with lower costs ($44,226/patient vs. $44,811/patient respectively) and higher QALYs (12.85/patient vs. 12.70/patient, respectively). Ceftolozane/tazobactam + metronidazole remained the dominant choice in one-way and probabilistic sensitivity analyses. CONCLUSIONS: Based on surveillance data, ceftolozane/tazobactam is more likely to be an appropriate empiric therapy for cIAI in the US. Results from a decision-analytic simulation model indicate that use of ceftolozane/tazobactam + metronidazole would result in cost savings and improves QALYs, compared with piperacillin/tazobactam.

Cost-Effectiveness of Golimumab in Ankylosing Spondylitis from the UK Payer Perspective.

INTRODUCTION: Golimumab is a tumor necrosis factor-α (TNF-α) inhibitor for treatment of patients with severe, active ankylosing spondylitis. This study evaluated the cost-effectiveness of golimumab compared with conventional care and other TNF-α inhibitors in treatment of AS from the UK National Health Service perspective. METHODS: A long-term Markov model (with initial decision tree) was developed to simulate the progression of a hypothetical cohort of patients with active AS over a lifetime. The effectiveness outcome was quality-adjusted life-years (QALYs). Utilities were estimated by mapping Bath Ankylosing Spondylitis Functional Index scores, and the primary response measure was ≥50% improvement on the Bath Ankylosing Spondylitis Disease Activity Index at 12 weeks. Direct, medication, and AS management costs were included. Costs and outcomes were discounted at 3.5%. RESULTS: All TNF-α inhibitors were comparable to each other and superior to conventional care. The incremental cost-effectiveness ratios (ICERs) for TNF-α inhibitors were £19,070-42,532 per QALY gained compared with conventional care. Analyses of the ICERs for each TNF-α inhibitor compared with conventional care demonstrated that golimumab was the most cost-effective treatment, and that adalimumab and etanercept were dominated by golimumab. Sensitivity analyses confirmed the robustness of these analyses. CONCLUSIONS: Golimumab may be considered a cost-effective treatment alternative for patients with active AS. With comparable costs and efficacy among TNF-α inhibitors, the choice of TNF-α inhibitor to treat AS is likely to be driven by patient and physician choice. FUNDING: Merck & Co., Inc.

Cost-effectiveness of ceftolozane/tazobactam compared with piperacillin/tazobactam as empiric therapy based on the in-vitro surveillance of bacterial isolates in the United States for the treatment of complicated urinary tract infections.

BACKGROUND: A challenge in the empiric treatment of complicated urinary tract infection (cUTI) is identifying the initial appropriate antibiotic therapy (IAAT), which is associated with reduced length of stay and mortality compared with initial inappropriate antibiotic therapy (IIAT). We evaluated the cost-effectiveness of ceftolozane/tazobactam compared with piperacillin/tazobactam (one of the standard of care antibiotics), for the treatment of hospitalized patients with cUTI. METHODS: A decision-analytic Monte Carlo simulation model was developed to compare the costs and effectiveness of empiric treatment with either ceftolozane/tazobactam or piperacillin/tazobactam in hospitalized adult patients with cUTI infected with Gram-negative pathogens in the US. The model applies the baseline prevalence of resistance as reported by national in-vitro surveillance data. RESULTS: In a cohort of 1000 patients, treatment with ceftolozane/tazobactam resulted in higher total costs compared with piperacillin/tazobactam ($36,413 /patient vs. $36,028/patient, respectively), greater quality-adjusted life years (QALYs) (9.19/patient vs. 9.13/patient, respectively) and an incremental cost-effectiveness ratio (ICER) of $6128/QALY. Ceftolozane/tazobactam remained cost-effective at a willingness to pay of $100,000 per QALY compared to piperacillin/tazobactam over a range of input parameter values during one-way and probabilistic sensitivity analysis. CONCLUSIONS: Model results show that ceftolozane/tazobactam is likely to be cost-effective compared with piperacillin/tazobactam for the empiric treatment of hospitalized cUTI patients in the United States.

Estimating the potential effects of a vaccine program against an emerging influenza pandemic--United States.

BACKGROUND: Human illness from influenza A(H7N9) was identified in March 2013, and candidate vaccine viruses were soon developed. To understand factors that may impact influenza vaccination programs, we developed a model to evaluate hospitalizations and deaths averted considering various scenarios. METHODS: We utilized a model incorporating epidemic curves with clinical attack rates of 20% or 30% in a single wave of illness, case hospitalization ratios of 0.5% or 4.2%, and case fatality ratios of 0.08% or 0.53%. We considered scenarios that achieved 80% vaccination coverage, various starts of vaccination programs (16 or 8 weeks before, the same week of, or 8 or 16 weeks after start of pandemic), an administration rate of 10 or 30 million doses per week (the latter rate is an untested assumption), and 2 levels of vaccine effectiveness (2 doses of vaccine required; either 62% or 80% effective for persons aged <60 years, and either 43% or 60% effective for persons aged ≥ 60 years). RESULTS: The start date of vaccination campaigns most influenced impact; 141,000-2,200,000 hospitalizations and 11,000-281,000 deaths were averted when campaigns started before a pandemic, and <100-1 300,000 hospitalizations and 0-165,000 deaths were averted for programs beginning the same time as or after the introduction of the pandemic virus. The rate of vaccine administration and vaccine effectiveness did not influence campaign impact as much as timing of the start of campaign. CONCLUSIONS: Our findings suggest that efforts to improve the timeliness of vaccine production will provide the greatest impacts for future pandemic vaccination programs.

Efficiency of points of dispensing for influenza A(H1N1)pdm09 vaccination, Los Angeles County, California, USA, 2009.

During October 23-December 8, 2009, the Los Angeles County Department of Public Health used points of dispensing (PODs) to improve access to and increase the number of vaccinations against influenza A(H1N1)pdm09. We assessed the efficiency of these units and access to vaccines among ethnic groups. An average of 251 persons per hour (SE 65) were vaccinated at the PODs; a 10% increase in use of live-attenuated monovalent vaccines reduced that rate by 23 persons per hour (SE 7). Vaccination rates were highest for Asians (257/10,000 persons), followed by Hispanics (114/10,000), whites (75/100,000), and African Americans (37/10,000). Average distance traveled to a POD was highest for whites (6.6 miles; SD 6.5) and lowest for Hispanics (4.7 miles; SD ±5.3). Placing PODs in areas of high population density could be an effective strategy to reach large numbers of persons for mass vaccination, but additional PODs may be needed to improve coverage for specific populations.

The Economics of Strategies to Reduce Respiratory Syncytial Virus Hospitalizations in Alaska.

BACKGROUND: Alaska Native infants experience high rates of respiratory syncytial virus (RSV) hospitalizations. Through 2008, Alaska administered a 7-dose (maximum) palivizumab regime to high-risk infants from October to May. In 2009, the maximum was reduced to 3 doses for 32- to 34-week preterm babies and 6 doses for other groups. METHODS: We used 11 years of data and regional Medicaid reimbursement rates to model the cost effectiveness of 4 palivizumab intervention strategies to reduce RSV hospitalizations among Alaskan infants including: current strategy, old strategy (1998-2008), and 2 hypothetical strategies using the current strategy plus 1 or 3 doses to all newborn infants during the RSV season. RESULTS: The current strategy represents 5 hospitalizations averted per year for the palivizumab cohort (∼50-56 children) at ∼$52 846 per hospitalization averted, compared with no intervention. Compared with the old strategy, the mean cost per hospitalization prevented for the current strategy was 63% lower, net program costs were 85% lower, and the mean hospitalizations prevented were 27% lower. Compared with current strategy only, the addition of 1 dose to all newborns during the RSV season could decrease the mean cost per hospitalization prevented by 23%, increase the number of hospitalizations prevented by 2.5-fold, and increase the net programmatic costs by 3.3-fold; administering up to 3 doses to infants further reduced hospitalizations and increased costs. CONCLUSIONS: The current palivizumab strategy improved the cost-effectiveness ratio compared with the old strategy. Further improvement could be obtained by adding doses for Alaskan Native newborns during the RSV season; however, programmatic costs would increase.

Modeling the effect of water, sanitation, and hygiene and oral cholera vaccine implementation in Haiti.

In 2010, toxigenic Vibrio cholerae was newly introduced to Haiti. Because resources are limited, decision-makers need to understand the effect of different preventive interventions. We built a static model to estimate the potential number of cholera cases averted through improvements in coverage in water, sanitation and hygiene (WASH) (i.e., latrines, point-of-use chlorination, and piped water), oral cholera vaccine (OCV), or a combination of both. We allowed indirect effects and non-linear relationships between effect and population coverage. Because there are limited incidence data for endemic cholera in Haiti, we estimated the incidence of cholera over 20 years in Haiti by using data from Malawi. Over the next two decades, scalable WASH interventions could avert 57,949-78,567 cholera cases, OCV could avert 38,569-77,636 cases, and interventions that combined WASH and OCV could avert 71,586-88,974 cases. Rate of implementation is the most influential variable, and combined approaches maximized the effect.

Effects of vaccine program against pandemic influenza A(H1N1) virus, United States, 2009-2010.

In April 2009, the United States began a response to the emergence of a pandemic influenza virus strain: A(H1N1)pdm09. Vaccination began in October 2009. By using US surveillance data (April 12, 2009-April 10, 2010) and vaccine coverage estimates (October 3, 2009-April 18, 2010), we estimated that the A(H1N1)pdm09 virus vaccination program prevented 700,000-1,500,000 clinical cases, 4,000-10,000 hospitalizations, and 200-500 deaths. We found that the national health effects were greatly influenced by the timing of vaccine administration and the effectiveness of the vaccine. We estimated that recommendations for priority vaccination of targeted priority groups were not inferior to other vaccination prioritization strategies. These results emphasize the need for relevant surveillance data to facilitate a rapid evaluation of vaccine recommendations and effects.

Prevalence of 2009 pandemic influenza A (H1N1) virus antibodies, Tampa Bay Florida--November-December, 2009.

BACKGROUND: In 2009, a novel influenza virus (2009 pandemic influenza A (H1N1) virus (pH1N1)) caused significant disease in the United States. Most states, including Florida, experienced a large fall wave of disease from September through November, after which disease activity decreased substantially. We determined the prevalence of antibodies due to the pH1N1 virus in Florida after influenza activity had peaked and estimated the proportion of the population infected with pH1N1 virus during the pandemic. METHODS: During November-December 2009, we collected leftover serum from a blood bank, a pediatric children's hospital and a pediatric outpatient clinic in Tampa Bay Florida. Serum was tested for pH1N1 virus antibodies using the hemagglutination-inhibition (HI) assay. HI titers ≥40 were considered seropositive. We adjusted seroprevalence results to account for previously established HI assay specificity and sensitivity and employed a simple statistical model to estimate the proportion of seropositivity due to pH1N1 virus infection and vaccination. RESULTS: During the study time period, the overall seroprevalence in Tampa Bay, Florida was 25%, increasing to 30% after adjusting for HI assay sensitivity and specificity. We estimated that 5.9% of the population had vaccine-induced seropositivity while 25% had seropositivity secondary to pH1N1 virus infection. The highest cumulative incidence of pH1N1 virus infection was among children aged 5-17 years (53%) and young adults aged 18-24 years (47%), while adults aged ≥50 years had the lowest cumulative incidence (11-13%) of pH1N1 virus infection. CONCLUSIONS: After the peak of the fall wave of the pandemic, an estimated one quarter of the Tampa Bay population had been infected with the pH1N1 virus. Consistent with epidemiologic trends observed during the pandemic, the highest burdens of disease were among school-aged children and young adults.

Estimating effect of antiviral drug use during pandemic (H1N1) 2009 outbreak, United States.

From April 2009 through March 2010, during the pandemic (H1N1) 2009 outbreak, ≈8.2 million prescriptions for influenza neuraminidase-inhibiting antiviral drugs were filled in the United States. We estimated the number of hospitalizations likely averted due to use of these antiviral medications. After adjusting for prescriptions that were used for prophylaxis and personal stockpiles, as well as for patients who did not complete their drug regimen, we estimated the filled prescriptions prevented ≈8,400-12,600 hospitalizations (on the basis of median values). Approximately 60% of these prevented hospitalizations were among adults 18-64 years of age, with the remainder almost equally divided between children 0-17 years of age and adults >65 years of age. Public health officials should consider these estimates an indication of success of treating patients during the 2009 pandemic and a warning of the need for renewed planning to cope with the next pandemic.

Closing schools in response to the 2009 pandemic influenza A H1N1 virus in New York City: economic impact on households.

Understanding the effectiveness of a school closure in limiting social interaction and the economic impact of school closure on households is critical when developing guidelines to prevent spread of pandemic influenza. A New York City survey conducted in June 2009 in 554 households affected by the 2009 pandemic influenza H1N1-related school closures showed that, during closure, 30% of students visited at least 1 locale outside their homes. If all the adults in the home were employed, an ill child was less likely to leave home. In 17% of the households, at least 1 adult missed some work because of the closure. If all adults in the home were employed, someone was more likely to take time off work. If other children were in the household, it was less likely that an adult took time off work. The findings of our study will be important when developing future pandemic school-closure guidance.

Estimating the burden of 2009 pandemic influenza A (H1N1) in the United States (April 2009-April 2010).

To calculate the burden of 2009 pandemic influenza A (pH1N1) in the United States, we extrapolated from the Centers for Disease Control and Prevention's Emerging Infections Program laboratory-confirmed hospitalizations across the entire United States, and then corrected for underreporting. From 12 April 2009 to 10 April 2010, we estimate that approximately 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (195,086-402,719), and 12,469 deaths (8868-18,306) occurred in the United States due to pH1N1. Eighty-seven percent of deaths occurred in those under 65 years of age with children and working adults having risks of hospitalization and death 4 to 7 times and 8 to 12 times greater, respectively, than estimates of impact due to seasonal influenza covering the years 1976-2001. In our study, adults 65 years of age or older were found to have rates of hospitalization and death that were up to 75% and 81%, respectively, lower than seasonal influenza. These results confirm the necessity of a concerted public health response to pH1N1.