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During the 2022-23 influenza season, early increases in influenza activity, co-circulation of influenza with other respiratory viruses, and high influenza-associated hospitalization rates, particularly among children and adolescents, were observed. This report describes the 2022-23 influenza season among children and adolescents aged <18 years, including the seasonal severity assessment; estimates of U.S. influenza-associated medical visits, hospitalizations, and deaths; and characteristics of influenza-associated hospitalizations. The 2022-23 influenza season had high severity among children and adolescents compared with thresholds based on previous seasons' influenza-associated outpatient visits, hospitalization rates, and deaths. Nationally, the incidences of influenza-associated outpatient visits and hospitalization for the 2022-23 season were similar for children aged <5 years and higher for children and adolescents aged 5-17 years compared with previous seasons. Peak influenza-associated outpatient and hospitalization activity occurred in late November and early December. Among children and adolescents hospitalized with influenza during the 2022-23 season in hospitals participating in the Influenza Hospitalization Surveillance Network, a lower proportion were vaccinated (18.3%) compared with previous seasons (35.8%-41.8%). Early influenza circulation, before many children and adolescents had been vaccinated, might have contributed to the high hospitalization rates during the 2022-23 season. Among symptomatic hospitalized patients, receipt of influenza antiviral treatment (64.9%) was lower than during pre-COVID-19 pandemic seasons (80.8%-87.1%). CDC recommends that all persons aged ≥6 months without contraindications should receive the annual influenza vaccine, ideally by the end of October., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Sue Kim reports institutional support from the Michigan Department of Health & Human Services and the Council of State and Territorial Epidemiologists (CSTE). Ruth Lynfield is a member of CSTE and serves on the program committee for ID Week and is an associate editor for the American Academy of Pediatrics’ (AAP) Red Book (for which she donated the received fee to the Minnesota Department of Health) and is an executive officer of CSTE and the National Foundation for Infectious Diseases (NFID). She receives support for attending meetings of CSTE, NFID, the Infectious Diseases Society of America, and AAP. Kimberly Yousey-Hindes reports receipt of an honorarium for delivering an invited lecture at Western Connecticut State University in October 2020, and receipt of support for travel to the International Influenza Assessor Training by CSTE in January 2023. No other potential conflicts of interest were disclosed.

When an influenza pandemic emerges, temporary school closures and antiviral treatment may slow virus spread, reduce the overall disease burden, and provide time for vaccine development, distribution, and administration while keeping a larger portion of the general population infection free. The impact of such measures will depend on the transmissibility and severity of the virus and the timing and extent of their implementation. To provide robust assessments of layered pandemic intervention strategies, the Centers for Disease Control and Prevention (CDC) funded a network of academic groups to build a framework for the development and comparison of multiple pandemic influenza models. Research teams from Columbia University, Imperial College London/Princeton University, Northeastern University, the University of Texas at Austin/Yale University, and the University of Virginia independently modeled three prescribed sets of pandemic influenza scenarios developed collaboratively by the CDC and network members. Results provided by the groups were aggregated into a mean-based ensemble. The ensemble and most component models agreed on the ranking of the most and least effective intervention strategies by impact but not on the magnitude of those impacts. In the scenarios evaluated, vaccination alone, due to the time needed for development, approval, and deployment, would not be expected to substantially reduce the numbers of illnesses, hospitalizations, and deaths that would occur. Only strategies that included early implementation of school closure were found to substantially mitigate early spread and allow time for vaccines to be developed and administered, especially under a highly transmissible pandemic scenario.

Background: The epidemiology of circulating seasonal influenza strains changed following the 2009 pandemic influenza A(H1N1). A universal influenza vaccination recommendation has been implemented and new vaccine types have become available post-2009. The objective of this study was to evaluate the cost-effectiveness of routine annual influenza vaccination in the context of this new evidence., Methods: A state transition simulation model was constructed to estimate the health and economic outcomes of influenza vaccination compared to no vaccination for hypothetical US cohorts stratified by age and risk status. Model input parameters were derived from multiple sources, including post-2009 vaccine effectiveness data from the US Flu Vaccine Effectiveness Network. The analysis used societal and healthcare sector perspectives and a one-year time horizon, except permanent outcomes were also included. The primary outcome was the incremental cost-effectiveness ratio (ICER) in dollars per quality-adjusted life years (QALYs) gained., Results: Compared to no vaccination, vaccination yielded ICERs lower than $95,000/QALY for all age and risk groups, except for non-high-risk adults 18-49 years ($194,000/QALY). Vaccination was cost-saving for adults ≥50 years at higher risk for influenza-related complications. Results were most sensitive to changes in the probability of influenza illness. Performing the analysis from the healthcare sector perspective, excluding vaccination time costs, delivering vaccinations in lower-cost settings, and including productivity losses improved the cost-effectiveness of vaccination. Sensitivity analysis revealed that vaccination remains below $100,000/QALY for older persons ≥65 years at vaccine effectiveness estimates as low as 4 %., Conclusions: Cost-effectiveness of influenza vaccination varied by age and risk status and was less than $95,000/QALY for all subgroups, except for non-high-risk working-age adults. Results were sensitive to the probability of influenza illness and vaccination was more favorable under certain scenarios. Vaccination for higher risk subgroups resulted in ICERs below $100,000/QALY even at low levels of vaccine effectiveness or circulating virus., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: High-dose, adjuvanted, and recombinant influenza vaccines may offer improved effectiveness among older adults compared with standard-dose, unadjuvanted, inactivated vaccines. However, the Advisory Committee on Immunization Practices (ACIP) only recently recommended preferential use of these "higher-dose or adjuvanted" vaccines. One concern was that individuals might delay or decline vaccination if a preferred vaccine is not readily available., Methods: We mathematically model how a recommendation for preferential use of higher-dose or adjuvanted vaccines in adults ≥65 years might impact influenza burden in the United States during exemplar "high-" and "low-"severity seasons. We assume higher-dose or adjuvanted vaccines are more effective than standard vaccines and that such a recommendation would increase uptake of the former but could cause (i) delays in administration of additional higher-dose or adjuvanted vaccines relative to standard vaccines and/or (ii) reductions in overall coverage if individuals only offered standard vaccines forego vaccination., Results: In a best-case scenario, assuming no delay or coverage reduction, a new recommendation could decrease hospitalizations and deaths in adults ≥65 years by 0%-4% compared with current uptake. However, intermediate and worst-case scenarios, with assumed delays of 3 or 6 weeks and/or 10% or 20% reductions in coverage, included projections in which hospitalizations and deaths increased by over 7%., Conclusions: We estimate that increased use of higher-dose or adjuvanted vaccines could decrease influenza burden in adults ≥65 in the United States provided there is timely and adequate access to these vaccines, and that standard vaccines are administered when they are unavailable., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background: During the 2009 influenza A(H1N1)pdm09 pandemic, 77 countries received donated monovalent A(H1N1)pdm09 vaccine through the WHO Pandemic Influenza A(H1N1) Vaccine Deployment Initiative. However, 47% did not receive their first shipment until after the first wave of virus circulation, and 8% did not receive their first shipment until after the WHO declared the end of the pandemic. Arguably, these shipments were too late into the pandemic to have a substantial effect on virus transmission or disease burden during the first waves of the pandemic., Objectives: In order to evaluate the potential benefits of earlier vaccine availability, we estimated the number of illnesses and deaths that could be averted during a 2009-like influenza pandemic under five different vaccine-availability timing scenarios., Methods: We adapted a model originally developed to estimate annual influenza morbidity and mortality burden averted through US seasonal vaccination and ran it for five vaccine availability timing scenarios in nine low- and middle-income countries that received donated vaccine., Results: Among nine study countries, we estimated that the number of averted cases was 61-216,197 for actual vaccine receipt, increasing to 2,914-283,916 had vaccine been available simultaneously with the United States., Conclusions: Earlier delivery of vaccines can reduce influenza case counts during a simulated 2009-like pandemic in some low- and middle-income countries. For others, increasing the number of cases and deaths prevented through vaccination may be dependent on factors other than timely initiation of vaccine administration, such as distribution and administration capacity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: There are few estimates of vaccination-averted influenza-associated illnesses in China., Methods: We used a mathematical model and Monte Carlo algorithm to estimate numbers and 95% confidence intervals (CI) of influenza-associated outcomes (hospitalization, illness, and medically-attended (MA) illness) averted by vaccination among children aged 6-59 months in Suzhou from October 2011-September 2016. Influenza illnesses included non-hospitalized MA influenza illnesses and non-MA influenza illnesses. The numbers of influenza-associated outcomes averted by vaccination were the difference between the expected burden if there were no vaccination given and the observed burden with vaccination. The model incorporated the disease burden estimated based on surveillance data from Suzhou University Affiliated Children's Hospital (SCH) and data from health utilization surveys conducted in the catchment area of SCH, age-specific estimates of influenza vaccination coverage in Suzhou from the Expanded Program on Immunization database, and influenza vaccine effectiveness estimates from previous publications. Averted influenza estimations were presented as absolute numbers and in terms of the prevented fraction (PF). A hypothetical scenario with 50% coverage (but identical vaccine effectiveness) over the study period was also modeled., Results: In ~250,000 children, influenza vaccination prevented an estimated 731 (CI: 549-960) influenza hospitalizations (PF: 6.2% of expected, CI: 5.8-6.6%) and 10,024 (7593-12,937) influenza illnesses (PF: 6.5%, 6.4-6.7%), of which 8342 (6338-10,768) were MA (PF: 6.6%, 6.4-6.7%) from 2011 to 2016. The PFs declined each year along with decreasing influenza vaccination coverage. If 50% of the study population had been vaccinated over time, the estimated numbers of averted cases during the study period would have been 4059 (3120-5762) influenza hospitalizations (PF: 27.2%, 26.4-27.9%) and 56,215 (42,925-78,849) influenza illnesses (PF: 28.5%, 28.3-28.7%), of which 46,596 (35,662-65,234) would be MA (PF: 28.5%, 28.3-28.7%)., Conclusion: Influenza vaccination is estimated to have averted influenza-associated illness outcomes even with low coverage in children aged 6-59 months in Suzhou. Increasing influenza vaccination coverage in this population could further reduce illnesses and hospitalizations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: Coverage levels for many recommended adult vaccinations are low. The cost-effectiveness research literature on adult vaccinations has not been synthesized in recent years, which may contribute to low awareness of the value of adult vaccinations and to their under-utilization. We assessed research literature since 1980 to summarize economic evidence for adult vaccinations included on the adult immunization schedule., Methods: We searched PubMed, EMBASE, EconLit, and Cochrane Library from 1980 to 2016 and identified economic evaluation or cost-effectiveness analysis for vaccinations targeting persons aged ≥18 years in the U.S. or Canada. After excluding records based on title and abstract reviews, the remaining publications had a full-text review from two independent reviewers, who extracted economic values that compared vaccination to "no vaccination" scenarios., Results: The systematic searches yielded 1688 publications. After removing duplicates, off-topic publications, and publications without a "no vaccination" comparison, 78 publications were included in the final analysis (influenza = 25, pneumococcal = 18, human papillomavirus = 9, herpes zoster = 7, tetanus-diphtheria-pertussis = 9, hepatitis B = 9, and multiple vaccines = 1). Among outcomes assessing age-based vaccinations, the percent indicating cost-savings was 56% for influenza, 31% for pneumococcal, and 23% for tetanus-diphtheria-pertussis vaccinations. Among age-based vaccination outcomes reporting $/QALY, the percent of outcomes indicating a cost per QALY of ≤$100,000 was 100% for influenza, 100% for pneumococcal, 69% for human papillomavirus, 71% for herpes zoster, and 50% for tetanus-diphtheria-pertussis vaccinations., Conclusions: The majority of published studies report favorable cost-effectiveness profiles for adult vaccinations, which supports efforts to improve the implementation of adult vaccination recommendations., (Published by Elsevier Ltd.)

Background: Seasonal influenza causes considerable morbidity and mortality across all age groups, and influenza vaccination was recommended in 2010 for all persons aged 6 months and above. We estimated the averted costs due to influenza vaccination, taking into account the seasonal economic burden of the disease., Methods: We used recently published values for averted outcomes due to influenza vaccination for influenza seasons 2005-06, 2006-07, 2007-08, and 2008-09, and age cohorts 6 months-4 years, 5-19 years, 20-64 years, and 65 years and above. Costs were calculated according to a payer and societal perspective (in 2009 US$), and took into account medical costs and productivity losses., Results: When taking into account direct medical costs (payer perspective), influenza vaccination was cost saving only for the older age group (65≥) in seasons 2005-06 and 2007-08. Using the same perspective, influenza vaccination resulted in total costs of $US 1.7 billion (95%CI: $US 0.3-4.0 billion) in 2006-07 and $US 1.8 billion (95%CI: $US 0.1-4.1 billion) in 2008-09. When taking into account a societal perspective (and including the averted lost earnings due to premature death) averted deaths in the older age group influenced the results, resulting in cost savings for all ages combined in season 07-08., Discussion: Influenza vaccination was cost saving in the older age group (65≥) when taking into account productivity losses and, in some seasons, when taking into account medical costs only. Averted costs vary significantly per season; however, in seasons where the averted burden of deaths is high in the older age group, averted productivity losses due to premature death tilt overall seasonal results towards savings. Indirect vaccination effects and the possibility of diminished case severity due to influenza vaccination were not considered, thus the averted burden due to influenza vaccine may be even greater than reported.

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., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Pregnant women and infants are at increased risk of severe disease from influenza. Antenatal influenza vaccination is safe and can reduce the risk of illness for women and their infants. We evaluated for South Africa the health effects of antenatal influenza vaccination among pregnant women and their infants aged <6 months old and assessed its cost-effectiveness. We constructed a decision tree model to simulate the population of pregnant women and infants aged <6 months in South Africa using TreeAge Pro Suite 2015. The model evaluated the change in societal costs and outcomes associated with a vaccination campaign that prioritized HIV-infected over HIV-uninfected pregnant women compared with no vaccination. We also examined the impacts of a campaign without prioritization. Upper and lower 90% uncertainty intervals (90% UI) were generated using probabilistic sensitivity analysis on 10000 Monte Carlo simulations. The cost-effectiveness threshold was set to the 2015 per capita gross domestic product of South Africa, US$5724. Antenatal vaccination with prioritization averted 9070 (90% UI: 7407–11217) total cases of influenza among pregnant women and infants, including 411 (90% UI: 305–546) hospitalizations and 30 (90% UI: 22–40) deaths. This corresponds to an averted fraction of 13.5% (90% UI: 9.0–20.5%). Vaccinating without prioritization averted 7801 (90% UI: 6465–9527) cases of influenza, including 335 (90% UI: 254–440) hospitalizations and 24 (90% UI: 18–31) deaths. This corresponds to an averted fraction of 11.6% (90% UI: 7.8–17.4%). Vaccinating the cohort of pregnant women with prioritization had societal cost of $4689 (90% UI: $3128–$7294) per Quality Adjusted Life Year (QALY) gained while vaccinating without prioritization had a cost of $5924 (90% UI: $3992–$9056) per QALY. Antenatal influenza vaccination campaigns in South Africa would reduce the impact of influenza and could be cost-effective. [ABSTRACT FROM AUTHOR]

• We assessed economic burden of influenza in children <5 in Suzhou from 2011-2017. • Cost per illness episode was $161 for outpatient and $1426 for hospitalization. • Annual economic burden of influenza among children <5 in Suzhou was $7.4 million. • Indirect costs accounted for 22-36% of the total annual economic burden. • Influenza in children <5 in Suzhou results in a substantial annual economic burden. Data are limited on the economic burden of seasonal influenza in China. We estimated the cost due to influenza illness among children < 5-year-old in Suzhou, China. This study adopted a societal perspective to estimate direct medical cost, direct non-medical cost, and indirect cost related to lost productivity. Data to calculate costs and rates of three influenza illness outcomes (non-medically attended, outpatient and hospitalization) were collected from prospective community-based cohort studies and hospital-based enhanced laboratory-confirmed influenza surveillance in Suzhou during the 2011/12 to 2016/17 influenza seasons. We used mean cost-per-episode, annual incidence rates of episodes of each outcome, and annual population size to estimate the total annual economic burden of influenza illnesses among children < 5-year-old for Suzhou. All costs were reported in 2017 U.S. dollars. The mean cost-per-episode (standard deviation) was $9.92 (13.26) for non-medically attended influenza, $161.05 (176.98) for influenza outpatient illnesses, and $1425.95 (603.59) for influenza hospitalizations. By applying the annual incidence rates to the population size, we estimated an annual total of 4,919 episodes of non-medically attended influenza, 21,994 influenza outpatient, and 2,633 influenza hospitalization. Total annual economic burden of influenza to society among children < 5-year-old in Suzhou was $7.37 (95% confidence interval, 6.9–7.8) million, with estimated costs for non-medically attended influenza of $49,000 (46,000–52,000), influenza outpatients $3.5 (3.3–3.8) million, and influenza hospitalizations $3.8 (3.6–3.9) million. Among outpatients, the indirect cost was 36.3% ($1.3 million) of total economic burden, accounting for 21,994 days of lost productivity annually. Among inpatients, the indirect cost was 22.1% ($829,000), accounting for 18,431 days of lost productivity annually. Our findings show that influenza in children < 5-year-oldcauses substantial societal economic burden in Suzhou, China. Assessing the potential economic benefit of increasing influenza vaccination coverage in this population is warranted. [ABSTRACT FROM AUTHOR]