Influenza Virus Vaccines Commons^™

Interim Estimates Of 2025-26 Seasonal Influenza Vaccine Effectiveness - United States, September 2025-February 2026., Patrick Maloney, Emily L. Reeves, Kristina Wielgosz, Ashley M. Price, Karthik Natarajan, Malini B. Desilva, Kristin Dascomb, Nicola P. Klein, Sara Y. Tartof, Stephanie A. Irving, Shaun J. Grannis, Toan C. Ong, Zachary A. Weber, Jennifer E. Schuster, Danielle M. Zerr, Marian G. Michaels, Julie A. Boom, Natasha B. Halasa, Mary A. Staat, Geoffrey A. Weinberg, Stacey L. House, Elie A. Saade, Krissy Moehling Geffel, Manjusha Gaglani, Karen J. Wernli, Vel Murugan, Emily T. Martin, Natalie A B Bontrager, Marie K. Kirby, Amanda B. Payne, Fatimah S. Dawood, Ayzsa Tannis, Heidi L. Moline, Sifang Kathy Zhao, Katherine Adams, Jennifer Decuir, Samantha M. Olson, Jessie R. Chung, Nathaniel Lewis, Brendan Flannery, Carrie Reed, Shikha Garg, Sascha Ellington, Cdc Influenza Vaccine Effectiveness Collaborators

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In the United States, annual influenza vaccination has been recommended for all persons aged ≥6 months, including during the 2025-26 season. Interim influenza vaccine effectiveness (VE) estimates were calculated for patients with acute respiratory illness-associated outpatient visits and hospitalizations from three U.S. respiratory virus VE networks during the 2025-26 influenza season, using a test-negative case-control design. Among children and adolescents aged < 18 years, VE was 38%-41% against influenza outpatient visits and 41% against influenza-associated hospitalization. Among adults aged ≥18 years, VE was 22%-34% against influenza outpatient visits and 30% against influenza-associated hospitalization. Among children and adolescents, VE against influenza A ranged from 37% (against outpatient visits) to 42% (against hospitalization) across settings; among adults, VE against influenza A ranged from 30% (against hospitalization) to 34% (against outpatient visits) across settings. Among children and adolescents, VE against influenza A(H3N2)-associated outpatient visits was 35% and against influenza A(H3N2)-associated hospitalization was 38%. VE against influenza B outpatient visits ranged from 45%-71% among children and adolescents and was 63% among adults. Other estimates of VE were not statistically significant or were not reportable. Although interim influenza VE is lower during the 2025-26 influenza season than it was during recent influenza seasons, these findings demonstrate that influenza vaccination still provides protection against influenza. CDC recommends influenza vaccination; U.S. influenza vaccines remain available for persons aged ≥6 months.

Interim Estimates Of 2024-2025 Seasonal Influenza Vaccine Effectiveness - Four Vaccine Effectiveness Networks, United States, October 2024-February 2025., Aaron M. Frutos, Seana Cleary, Emily L. Reeves, Haris M. Ahmad, Ashley M. Price, Wesley H. Self, Yuwei Zhu, Basmah Safdar, Ithan D. Peltan, Kevin W. Gibbs, Matthew C. Exline, Adam S. Lauring, Sarah W. Ball, Malini Desilva, Sara Y. Tartof, Kristin Dascomb, Stephanie A. Irving, Nicola P. Klein, Brian E. Dixon, Toan C. Ong, Ivana A. Vaughn, Stacey L. House, Kiran A. Faryar, Mary Patricia Nowalk, Manjusha Gaglani, Karen J. Wernli, Vel Murugan, Olivia L. Williams, Rangaraj Selvarangan, Geoffrey A. Weinberg, Mary A. Staat, Natasha B. Halasa, Leila C. Sahni, Marian G. Michaels, Janet A. Englund, Marie K. Kirby, Diya Surie, Fatimah S. Dawood, Benjamin R. Clopper, Heidi L Moline, Ruth Link-Gelles, Amanda B. Payne, Elizabeth Harker, Kristina Wielgosz, Zachary A. Weber, Duck-Hye Yang, Nathaniel M. Lewis, Jennifer Decuir, Samantha M. Olson, Jessie R. Chung, Brendan Flannery, Lisa A. Grohskopf, Carrie Reed, Shikha Garg, Sascha Ellington, Cdc Influenza Vaccine Effectiveness Collaborators

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Annual influenza vaccination is recommended for all persons aged ≥6 months in the United States. Interim influenza vaccine effectiveness (VE) was calculated among patients with acute respiratory illness-associated outpatient visits and hospitalizations from four VE networks during the 2024-25 influenza season (October 2024-February 2025). Among children and adolescents agedyears, VE against any influenza was 32%, 59%, and 60% in the outpatient setting in three networks, and against influenza-associated hospitalization was 63% and 78% in two networks. Among adults aged ≥18 years, VE in the outpatient setting was 36% and 54% in two networks and was 41% and 55% against hospitalization …

Immunogenicity And Reactogenicity Of High- Or Standard-Dose Influenza Vaccine In A Second Consecutive Influenza Season., Hannah Bahakel, Andrew J. Spieker, Haya Hayek, Jennifer E. Schuster, Lubna Hamdan, Daniel E. Dulek, Carrie L. Kitko, Tess Stopczynski, Einas Batarseh, Zaid Haddadin, Laura S. Stewart, Anna Stahl, Molly Potter, Herdi Rahman, Justin Amarin, Spyros A. Kalams, Claire E. Bocchini, Elizabeth A. Moulton, Susan E. Coffin, Monica I. Ardura, Rachel L. Wattier, Gabriela Maron, Michael Grimley, Grant Paulsen, Christopher J. Harrison, Jason Freedman, Paul A. Carpenter, Janet A. Englund, Flor M. Munoz, Lara Danziger-Isakov, Natasha Halasa, Pediatric Hct Flu Study

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BACKGROUND: Pediatric hematopoietic cell transplant (HCT) recipients are at high risk for morbidity from influenza virus infection. We demonstrated in a primary phase 2 randomized controlled trial that 2 post-HCT doses of high-dose trivalent influenza vaccine (HD-TIV) given 4 weeks apart were more immunogenic than 2 doses of standard-dose quadrivalent influenza vaccine (SD-QIV). Herein, we present the immunogenicity and safety of influenza vaccination in a consecutive season post-HCT using the same dosing regimen.

METHODS: A subcohort of study participants reenrolled and had hemagglutinin inhibition titers measured at baseline and 4 weeks after each vaccine dose in year 2. We estimated …

Influenza Knowledge And Barriers To Vaccination In Immunosuppressed Patients In The Pediatric Rheumatology Clinic., Julia G. Harris, Leslie Favier, Jordan T. Jones, Maria Ibarra, Michael J. Holland, Emily Fox, Kelly Jensen, Ashley K. Sherman, Ashley M. Cooper

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BACKGROUND: Most patients with a pediatric rheumatic disease are at increased risk of influenza due to immunosuppressive medication use. Despite initial quality improvement efforts, our influenza vaccination rate plateaued at 72%, which prompted a survey of patients and families to assess provider vaccine recommendations, influenza knowledge, and barriers to influenza vaccination.

METHODS: Patients on immunosuppressive medication or their parent were eligible to complete a survey between July 2019 and January 2020. Survey questions assessed demographics, rheumatology diagnosis, immunosuppressive medication(s), influenza vaccination recommendation, patient/parent influenza knowledge, and barriers to influenza vaccination. Influenza vaccination rates for immunosuppressed patients were acquired each influenza …

Estimated Vaccine Effectiveness For Pediatric Patients With Severe Influenza, 2015-2020., Kelsey M. Sumner, Leila C. Sahni, Julie A. Boom, Natasha B. Halasa, Laura S. Stewart, Janet A. Englund, Eileen J. Klein, Mary A. Staat, Elizabeth P. Schlaudecker, Rangaraj Selvarangan, Christopher J. Harrison, Geoffrey A. Weinberg, Peter G. Szilagyi, Monica N. Singer, Parvin H. Azimi, Benjamin R. Clopper, Heidi L. Moline, Emma K. Noble, John V. Williams, Marian G. Michaels, Samantha M. Olson, New Vaccine Surveillance Network Collaborators

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IMPORTANCE: Increasing the understanding of vaccine effectiveness (VE) against levels of severe influenza in children could help increase uptake of influenza vaccination and strengthen vaccine policies globally.

OBJECTIVE: To investigate VE in children by severity of influenza illness.

DESIGN, SETTING, AND PARTICIPANTS: This case-control study with a test-negative design used data from 8 participating medical centers located in geographically different US states in the New Vaccine Surveillance Network from November 6, 2015, through April 8, 2020. Participants included children 6 months through 17 years of age who were hospitalized or presented to an emergency department (ED) with acute respiratory illness. …

Interim Estimates Of 2023-24 Seasonal Influenza Vaccine Effectiveness - United States., Aaron M. Frutos, Ashley M. Price, Elizabeth Harker, Emily L. Reeves, Haris M. Ahmad, Vel Murugan, Emily T. Martin, Stacey House, Elie A. Saade, Richard K. Zimmerman, Manjusha Gaglani, Karen J. Wernli, Emmanuel B. Walter, Marian G. Michaels, Mary A. Staat, Geoffrey A. Weinberg, Rangaraj Selvarangan, Julie A. Boom, Eileen J. Klein, Natasha B. Halasa, Adit A. Ginde, Kevin W. Gibbs, Yuwei Zhu, Wesley H. Self, Sara Y. Tartof, Nicola P. Klein, Kristin Dascomb, Malini B. Desilva, Zachary A. Weber, Duck-Hye Yang, Sarah W. Ball, Diya Surie, Jennifer Decuir, Fatimah S. Dawood, Heidi L. Moline, Ariana P. Toepfer, Benjamin R. Clopper, Ruth Link-Gelles, Amanda B. Payne, Jessie R. Chung, Brendan Flannery, Nathaniel M. Lewis, Samantha M. Olson, Katherine Adams, Mark W. Tenforde, Shikha Garg, Lisa A. Grohskopf, Carrie Reed, Sascha Ellington, Cdc Influenza Vaccine Effectiveness Collaborators

Manuscripts, Articles, Book Chapters and Other Papers

In the United States, annual influenza vaccination is recommended for all persons aged ≥6 months. Using data from four vaccine effectiveness (VE) networks during the 2023-24 influenza season, interim influenza VE was estimated among patients aged ≥6 months with acute respiratory illness-associated medical encounters using a test-negative case-control study design. Among children and adolescents aged 6 months-17 years, VE against influenza-associated outpatient visits ranged from 59% to 67% and against influenza-associated hospitalization ranged from 52% to 61%. Among adults aged ≥18 years, VE against influenza-associated outpatient visits ranged from 33% to 49% and against hospitalization from 41% to 44%. VE …

Clinical Influenza Testing Practices In Hospitalized Children At United States Medical Centers, 2015-2018., Mark W. Tenforde, Angela P. Campbell, Marian G. Michaels, Christopher J. Harrison, Eileen J. Klein, Janet A. Englund, Rangaraj Selvarangan, Natasha B. Halasa, Laura S. Stewart, Geoffrey A. Weinberg, John V. Williams, Peter G. Szilagyi, Mary A. Staat, Julie A. Boom, Leila C. Sahni, Monica N. Singer, Parvin H. Azimi, Richard K. Zimmerman, Monica M. Mcneal, H Keipp Talbot, Arnold S. Monto, Emily T. Martin, Manjusha Gaglani, Fernanda P. Silveira, Donald B. Middleton, Jill M. Ferdinands, Melissa A. Rolfes

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At nine US hospitals that enrolled children hospitalized with acute respiratory illness (ARI) during 2015-2016 through 2017-2018 influenza seasons, 50% of children with ARI received clinician-initiated testing for influenza and 35% of cases went undiagnosed due to lack of clinician-initiated testing. Marked heterogeneity in testing practice was observed across sites.

Cost Effectiveness Of School-Located Influenza Vaccination Programs For Elementary And Secondary School Children., Byung-Kwang Yoo, Stanley J. Schaffer, Sharon Humiston, Cynthia M. Rand, Nicolas P N Goldstein, Christina S. Albertin, Cathleen Concannon, Peter G. Szilagyi

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BACKGROUND: Studies have noted variations in the cost-effectiveness of school-located influenza vaccination (SLIV), but little is known about how SLIV's cost-effectiveness may vary by targeted age group (e.g., elementary or secondary school students), or vaccine consent process (paper-based or web-based). Further, SLIV's cost-effectiveness may be impacted by its spillover effect on practice-based vaccination; prior studies have not addressed this issue.

METHODS: We performed a cost-effectiveness analysis on two SLIV programs in upstate New York in 2015-2016: (a) elementary school SLIV using a stepped wedge design with schools as clusters (24 suburban and 18 urban schools) and (b) secondary school SLIV …

Haemophilus Influenzae Type B Invasive Disease In Amish Children, Missouri, Usa, 2014, Angela L. Myers, Mary Anne Jackson, Lixin Zhang, Douglas S. Swanson, Janet R. Gilsdorf

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© 2017, Centers for Disease Control and Prevention (CDC). All rights reserved. During 5 months in 2014, three Amish children in Missouri, USA, were diagnosed with invasive Haemophilus influenzae type b infection. Two were rural neighbors infected with a genetically similar rare strain, sequence type 45. One child had recently traveled, raising the possibility of maintenance of this strain among unvaccinated carriers in Amish communities.

School-Located Influenza Vaccinations: A Randomized Trial., Peter G. Szilagyi, Stanley Schaffer, Cynthia M. Rand, Phyllis Vincelli, Ashley Eagan, Nicolas P N Goldstein, A Dirk Hightower, Mary Younge, Aaron Blumkin, Christina S. Albertin, Byung-Kwang Yoo, Sharon Humiston

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OBJECTIVE: Assess impact of offering school-located influenza vaccination (SLIV) clinics using both Web-based and paper consent upon overall influenza vaccination rates among elementary school children.

METHODS: We conducted a cluster-randomized trial (stratified by suburban/urban districts) in upstate New York in 2014-2015. We randomized 44 elementary schools, selected similar pairs of schools within districts, and allocated schools to SLIV versus usual care (control). Parents of children at SLIV schools were sent information and vaccination consent forms via e-mail, backpack fliers, or both (depending on school preferences) regarding school vaccine clinics. Health department nurses conducted vaccine clinics and billed insurers. For all …

Cost Effectiveness Analysis Of Year 2 Of An Elementary School-Located Influenza Vaccination Program-Results From A Randomized Controlled Trial., Byung-Kwang Yoo, Sharon Humiston, Peter G. Szilagyi, Stanley J. Schaffer, Christine Long, Maureen Kolasa

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BACKGROUND: School-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).

METHODS: We 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; …