Influenza Humans 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

Manuscripts, Articles, Book Chapters and Other Papers

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.

Changes In Antiviral Prescribing For Children With Influenza In Us Emergency Departments., Tess Stopczynski, Olla Hamdan, Justin Z. Amarin, James W. Antoon, Laura S. Stewart, Haya Hayek, James Chappell, Andrew J. Spieker, Eileen J. Klein, Janet A. Englund, Geoffrey A. Weinberg, Peter G. Szilagyi, John V. Williams, Marian G. Michaels, Julie A. Boom, Leila C. Sahni, Mary Allen Staat, Elizabeth P. Schlaudecker, Jennifer E. Schuster, Rangaraj Selvarangan, Ayzsa Tannis, Heidi L. Moline, Samantha M. Olson, Natasha B. Halasa

Manuscripts, Articles, Book Chapters and Other Papers

IMPORTANCE: Despite national recommendations, antiviral prescribing in emergency departments (EDs) for children at higher risk of severe influenza, such as those younger than 5 years and those with specific underlying conditions, remains low.

OBJECTIVE: To assess whether there were changes in antiviral prescribing for children at higher risk of severe influenza in academic pediatric EDs before the COVID-19 pandemic (2016-2020) vs the late pandemic period (2021-2023).

DESIGN, SETTING, AND PARTICIPANTS: This multicenter, cross-sectional study included influenza-positive children younger than 18 years presenting to the ED at 1 of 7 US pediatric academic hospitals participating in the Centers for Disease Control …

Antiviral Use Among Children Hospitalized With Laboratory-Confirmed Influenza Illness: A Prospective, Multicenter Surveillance Study., James W. Antoon, Justin Z. Amarin, Olla Hamdan, Tess Stopczynski, Laura S. Stewart, Marian G. Michaels, John V. Williams, Eileen J. Klein, Janet A. Englund, Geoffrey A. Weinberg, Peter G. Szilagyi, Jennifer E. Schuster, Rangaraj Selvarangan, Christopher J. Harrison, Julie A. Boom, Leila C. Sahni, Flor M. Muñoz, Mary Allen Staat, Elizabeth P. Schlaudecker, James D. Chappell, Benjamin R. Clopper, Heidi L. Moline, Angela P. Campbell, Andrew J. Spieker, Samantha M. Olson, Natasha B. Halasa

Manuscripts, Articles, Book Chapters and Other Papers

BACKGROUND: Guidelines state that all hospitalized children with suspected or confirmed influenza receive prompt treatment with influenza-specific antivirals. We sought to determine the frequency of, and factors associated with, antiviral receipt among hospitalized children.

METHODS: We conducted active surveillance of children presenting with fever or respiratory symptoms from 1 December 2016 to 31 March 2020 at 7 pediatric medical centers in the New Vaccine Surveillance Network. The cohort consisted of children hospitalized with influenza A or B confirmed by clinical or research testing. The primary outcome was frequency of antiviral receipt during hospitalization. We used logistic regression to obtain adjusted …

Clinical Testing For Covid-19, Influenza, And Rsv In Hospitalized Youths, 2016-2024., Ariana P. Toepfer, Rachel E. Rutkowski, Leila C. Sahni, Geoffrey A. Weinberg, Marian G. Michaels, Rangaraj Selvarangan, Mary Allen Staat, Natasha Halasa, Janet A. Englund, Julie A. Boom, Peter G. Szilagyi, Jennifer E. Schuster, Elizabeth P P. Schlaudecker, Laura S. Stewart, Eileen J. Klein, Samantha M. Olson, Sascha Ellington, Meredith L. Mcmorrow, Heidi L. Moline, Fatimah S. Dawood, New Vaccine Surveillance Network Collaborators

Manuscripts, Articles, Book Chapters and Other Papers

IMPORTANCE: Studies of COVID-19, influenza, and respiratory syncytial virus (RSV) disease clinical epidemiology, disease burden, and vaccine effectiveness often rely on clinical testing to identify cases, particularly with increasing use of electronic health record data. However, few data are available describing clinical testing practices to inform interpretation of these studies.

OBJECTIVE: To characterize clinical testing frequency for SARS-CoV-2, influenza, and RSV among children and adolescents hospitalized with acute respiratory illness during the 2016 to 2024 respiratory illness seasons by age, intensive care unit admission, and time period (2016-2020 and each season in 2020-2024); estimate the case fraction missed by clinical …

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

Manuscripts, Articles, Book Chapters and Other Papers

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

Manuscripts, Articles, Book Chapters and Other Papers

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 …

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

Manuscripts, Articles, Book Chapters and Other Papers

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. …

Underutilization Of Influenza Antiviral Treatment Among Children And Adolescents At Higher Risk For Influenza-Associated Complications - United States, 2023-2024., Aaron M. Frutos, Haris M. Ahmad, Dawud Ujamaa, Alissa C. O'Halloran, Janet A. Englund, Eileen J. Klein, Danielle M. Zerr, Melanie Crossland, Holly Staten, Julie A. Boom, Leila C. Sahni, Natasha B. Halasa, Laura S. Stewart, Olla Hamdan, Tess Stopczynski, William Schaffner, H Keipp Talbot, Marian G. Michaels, John V. Williams, Melissa Sutton, M Andraya Hendrick, Mary A. Staat, Elizabeth P. Schlaudecker, Brenda L. Tesini, Christina B. Felsen, Geoffrey A. Weinberg, Peter G. Szilagyi, Bridget J. Anderson, Jemma V. Rowlands, Murtada Khalifa, Marc Martinez, Rangaraj Selvarangan, Jennifer E. Schuster, Ruth Lynfield, Melissa Mcmahon, Sue Kim, Val Tellez Nunez, Patricia A. Ryan, Maya L. Monroe, Yun F. Wang, Kyle P. Openo, James Meek, Kimberly Yousey-Hindes, Nisha B. Alden, Isaac Armistead, Suchitra Rao, Shua J. Chai, Pam Daily Kirley, Ariana P. Toepfer, Fatimah S. Dawood, Heidi L. Moline, Timothy M. Uyeki, Sascha Ellington, Shikha Garg, Catherine H. Bozio, Samantha M. Olson

Manuscripts, Articles, Book Chapters and Other Papers

Annually, tens of thousands of U.S. children and adolescents are hospitalized with seasonal influenza virus infection. Both influenza vaccination and early initiation of antiviral treatment can reduce complications of influenza. Using data from two U.S. influenza surveillance networks for children and adolescents agedattended, laboratory-confirmed influenza for whom antiviral treatment is recommended, the percentage who received treatment was calculated. Trends in antiviral treatment of children and adolescents hospitalized with influenza from the 2017-18 to the 2023-2024 influenza seasons were also examined. Since 2017-18, when 70%-86% of hospitalized children and adolescents with influenza received antiviral treatment, the proportion receiving treatment notably declined. …

Accuracy Of Influenza Icd-10 Diagnosis Codes In Identifying Influenza Illness In Children., James W. Antoon, Tess Stopczynski, Justin Z. Amarin, Laura S. Stewart, Julie A. Boom, Leila C. Sahni, Marian G. Michaels, John V. Williams, Janet A. Englund, Eileen J. Klein, Mary A. Staat, Elizabeth P. Schlaudecker, Rangaraj Selvarangan, Jennifer E. Schuster, Geoffrey A. Weinberg, Peter G. Szilagyi, Ariana Perez, Heidi L. Moline, Andrew J. Spieker, Carlos G. Grijalva, Samantha M. Olson, Natasha B. Halasa

Manuscripts, Articles, Book Chapters and Other Papers

IMPORTANCE: Studies of influenza in children commonly rely on coded diagnoses, yet the ability of International Classification of Diseases, Ninth Revision codes to identify influenza in the emergency department (ED) and hospital is highly variable. The accuracy of newer International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes to identify influenza in children is unknown.

OBJECTIVE: To determine the accuracy of ICD-10 influenza discharge diagnosis codes in the pediatric ED and inpatient settings.

DESIGN, SETTING, AND PARTICIPANTS: Children younger than 18 years presenting to the ED or inpatient settings with fever and/or respiratory symptoms at 7 …

Pertussis And Influenza Immunization: Perceived Attitude And Decision Of Postpartum Patients, Nutan B Hebballi, Tayler Parker, Elisa I Garcia, Dalya M Ferguson, Susan Lesser, Kuojen Tsao, Maryam Broussard, Susan H Wootton

Faculty, Staff and Student Publications

BACKGROUND: Vaccination of pregnant patients with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) and influenza vaccine during influenza season can reduce maternal and fetal morbidity and mortality; nevertheless, vaccination rates remain suboptimal in this patient population. To investigate the effect of a brief educational counseling session on maternal Tdap and influenza vaccination and determine factors influencing women's decision in regards to receiving Tdap and or influenza vaccine during their pregnancy.

METHODS: A face-to-face semi-structured cross-sectional survey was administered to postpartum patients on their anticipated day of discharge (June 11-August 21, 2018). A brief educational counseling session about maternal …

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

Manuscripts, Articles, Book Chapters and Other Papers

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.

Efficacy Of Typhoid Conjugate Vaccine In Nepal: Final Results Of A Phase 3, Randomised, Controlled Trial, Mila Shakya, Merryn Voysey, Katherine Theiss-Nyland, Rachel Colin-Jones, Dikshya Pant, Anup Adhikari, Susan Tonks, Yama F Mujadidi, Peter O'Reilly, Olga Mazur, Sarah Kelly, Xinxue Liu, Archana Maharjan, Ashata Dahal, Naheeda Haque, Anisha Pradhan, Suchita Shrestha, Manij Joshi, Nicola Smith, Jennifer Hill, Jenny Clarke, Lisa Stockdale, Elizabeth Jones, Timothy Lubinda, Binod Bajracharya, Sabina Dongol, Abhilasha Karkey, Stephen Baker, Gordan Dougan, Virginia E Pitzer, Kathleen M Neuzil, Shrijana Shrestha, Buddha Basnyat, Andrew J Pollard

Faculty, Staff and Student Publications

BACKGROUND: Typhoid fever is a major public health problem in low-resource settings. Vaccination can help curb the disease and might reduce transmission. We have previously reported an interim analysis of the efficacy of typhoid conjugate vaccine (TCV) in Nepali children. Here we report the final results after 2 years of follow-up.

METHODS: We did a participant-masked and observer-masked individually randomised trial in Lalitpur, Nepal, in which 20 019 children aged 9 months to younger than 16 years were randomly assigned in a 1:1 ratio to receive a single dose of TCV (Typbar TCV, Bharat Biotech International, India) or capsular group …

Non-Mumps Viral Parotitis During The 2014-2015 Influenza Season In The United States., Lina I. Elbadawi, Pamela Talley, Melissa A. Rolfes, Alexander J. Millman, Erik Reisdorf, Natalie A. Kramer, John R. Barnes, Lenee Blanton, Jaime Christensen, Stefanie Cole, Tonya Danz, John J. Dreisig, Rebecca Garten, Thomas Haupt, Beth M. Isaac, Mary Anne Jackson, Anna Kocharian, Daniel Leifer, Karen Martin, Lisa Mchugh, Rebecca J. Mcnall, Jennifer Palm, Kay W. Radford, Sara Robinson, Jennifer B. Rosen, Senthilkumar K. Sakthivel, Peter Shult, Anna K. Strain, George Turabelidze, Lori A. Webber, Meghan Pearce Weinberg, David E. Wentworth, Brett L. Whitaker, Lyn Finelli, Michael A. Jhung, Ruth Lynfield, Jeffrey P. Davis

Manuscripts, Articles, Book Chapters and Other Papers

Background: During the 2014-2015 US influenza season, 320 cases of non-mumps parotitis (NMP) among residents of 21 states were reported to the Centers for Disease Control and Prevention (CDC). We conducted an epidemiologic and laboratory investigation to determine viral etiologies and clinical features of NMP during this unusually large occurrence.

Methods: NMP was defined as acute parotitis or other salivary gland swelling of >2 days duration in a person with a mumps- negative laboratory result. Using a standardized questionnaire, we collected demographic and clinical information. Buccal samples were tested at the CDC for selected viruses, including mumps, influenza, human parainfluenza …

Influenza-Associated Parotitis During The 2014-2015 Influenza Season In The United States., Melissa A. Rolfes, Alexander J. Millman, Pamela Talley, Lina I. Elbadawi, Natalie A. Kramer, Joh R. Barnes, Lenee Blanton, Jeffrey P. Davis, Stefanie Cole, John J. Dreisig, Rebecca Garten, Thomas Haupt, Mary Anne Jackson, Anna Kocharian, Daniel Leifer, Ruth Lynfield, Karen Martin, Lisa Mchugh, Sara Robinson, George Turabelidze, Lori A. Webber, Meghan Pearce Weinberg, David E. Wentworth, Lyn Finelli, Michael A. Jhung

Manuscripts, Articles, Book Chapters and Other Papers

Background: During the 2014-2015 influenza season in the United States, 256 cases of influenza-associated parotitis were reported from 27 states. We conducted a case-control study and laboratory investigation to further describe this rare clinical manifestation of influenza.

Methods: During February 2015-April 2015, we interviewed 50 cases (with parotitis) and 124 ill controls (without parotitis) with laboratory-confirmed influenza; participants resided in 11 states and were matched by age, state, hospital admission status, and specimen collection date. Influenza viruses were characterized using real-time polymerase chain reaction and next-generation sequencing. We compared cases and controls using conditional logistic regression. Specimens from additional reported …