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Home › Conditions › Influenza

Influenza

Part of Orthomyxoviridae Infections

Subtypes of Influenza

Influenza A(H3N2) 5 Highly Pathogenic Avian Influenza A(H5N1) Virus Infection 1 Influenza-Associated Encephalitis 1 Influenza-Associated Encephalopathy 1 Invasive pulmonary aspergillosis following influenza 1 Avian Influenza A(H5) Infection 0 Influenza B/Victoria Virus Infection 0

66 published articles · Updated continuously

Clinical Trial Landscape

Clinical Trials for Influenza

437 trials tracked for Influenza: 234 in phase 3 or 4 and 60 with published results. The most-cited published study has 932 citations.

437Trials tracked
234Phase 3 & 4
0Recruiting
60With published results
Phase distribution
Phase 4 100 Phase 3 134 Phase 2 127 Phase 1 30 Other / NA 46
  1. Phase 3 A Study of S-033188 (Baloxavir Marboxil) Compared With Placebo or Oseltamivir in Otherwise Healthy Patients With Influenza Completed · 932 cited
  2. Phase 4 T-cell And General Immune Response to Seasonal Influenza Vaccine (SLVP018) Year 2, 2010 Completed · 335 cited
  3. Phase 4 T-cell And General Immune Response to Seasonal Influenza Vaccine (SLVP018) Year 3, 2011 Completed · 334 cited
  4. Phase 4 T-cell And General Immune Response to Seasonal Influenza Vaccine (SLVP018) - Year 1, 2009 Completed · 334 cited
  5. Phase 3 Protective Efficacy of Flublok® Quadrivalent Versus Licensed Inactivated Influenza Vaccine in Adults ≥50 Years of Age Completed · 287 cited
  6. Phase 4 Control of Epidemic Influenza Through a School-based Influenza Vaccination Program Completed · 277 cited
Show 44 more trials
  1. Phase 3 Study of S-033188 (Baloxavir Marboxil) Compared With Placebo or Oseltamivir in Patients With Influenza at High Risk of Influenza Complications Completed · 265 cited
  2. Phase 3 Efficacy, Safety, and Immunogenicity of a Plant-Derived Quadrivalent Virus-Like Particles (VLPs) Influenza Vaccine in Adults Completed · 194 cited
  3. Phase 3 Immunogenicity, Safety, Reactogenicity, Efficacy, Effectiveness and Lot Consistency of FluBlok Completed · 161 cited
  4. Phase 4 Comparison of Immune Responses to Influenza Vaccine In Adults of Different Ages (SLVP015 2007-2017) Completed · 152 cited
  5. Phase 4 Pilot Study in Young Adults to Examine the Kinetics of Changes in the B-cell Repertoire Following TIV Immunization Completed · 142 cited
  6. Phase 3 Safety and Efficacy of H1N1 Vaccines in Children Aged 6 Months to Less Than 10 Years of Age Completed · 141 cited
  7. Phase 3 Study to Assess Efficacy and Safety of Baloxavir Marboxil In Combination With Standard-of-Care Neuraminidase Inhibitor In Hospitalized Participants With Severe Influenza Completed · 136 cited
  8. Phase 3 Study to Assess the Safety, Pharmacokinetics, and Efficacy of Baloxavir Marboxil in Healthy Pediatric Participants With Influenza-Like Symptoms Completed · 119 cited
  9. Phase 3 Efficacy Study of an Investigational Influenza Vaccine (Vero Cell Derived) to Prevent Culture Confirmed Influenza Infection (CCII) Completed · 100 cited
  10. Phase 3 Study to Evaluate the Safety and Immunogenicity of a Pandemic Influenza Vaccine in Adults Aged 18 Years and Above Completed · 94 cited
  11. Phase 3 Study to Evaluate Immunogenicity and Safety of an Investigational Influenza Vaccine (H1N1) in Adults Completed · 85 cited
  12. Phase 3 Safety and Immunogenicity of High-Dose Quadrivalent Influenza Vaccine in Participants ≥65 Years in the US Completed · 75 cited
  13. Phase 3 Lot-to-lot Consistency of a Plant-Derived Quadrivalent Virus-Like Particles Influenza Vaccine in Healthy Adults Completed · 72 cited
  14. Phase 3 Clinical Study to Evaluate the Safety, Immunogenicity and Efficacy of Investigational Flu Vaccine Compared to Approved Flu Vaccine in Children. Completed · 67 cited
  15. Phase 3 Safety and Immunogenicity of Flublok Quadrivalent vs IIV4 in Adults 18-49 Years of Age Completed · 58 cited
  16. Phase 4 B-cell Immunity to Influenza (SLVP017)- Year 1, 2009 Completed · 57 cited
  17. Phase 4 B-cell Immunity to Influenza (SLVP017) - Years 2 (2010) & 3 (2011) Completed · 57 cited
  18. Phase 4 Comparison of Three Licensed Influenza Vaccines Completed · 52 cited
  19. Phase 4 Effect of Age and Prior Immunity to Response to Seasonal Influenza Vaccines in Children Completed · 51 cited
  20. Phase 3 Clinical Study to Evaluate the Efficacy, Safety and Immunogenicity of an MF59-Adjuvanted Quadrivalent Influenza Vaccine Compared to Non-influenza Vaccine Comparator in Adults ≥ 65 Years of Age Completed · 48 cited
  21. Phase 4 Immunogenicity Trial of Egg- Versus Non-Egg-Based Influenza Vaccines Among HCP Completed · 46 cited
  22. Phase 4 Randomized Trial of High Dose Influenza Vaccine in Long Term Care Setting Completed · 46 cited
  23. Phase 4 Rapid Empiric Treatment With Oseltamivir Study (RETOS) Completed · 44 cited
  24. Phase 3 An Efficacy Study of GlaxoSmithKline (GSK) Biologicals' Candidate Influenza Vaccine GSK2321138A in Children Completed · 43 cited
  25. Phase 3 A Study of mRNA-1083 (SARS-CoV-2 and Influenza) Vaccine in Healthy Adult Participants, ≥50 Years of Age Completed · 39 cited
  26. Phase 3 Safety, Immunogenicity, and Relative Efficacy of H1N1 Vaccines in Adults Aged 18 Years and Older Completed · 39 cited
  27. Phase 3 Study to Assess the Efficacy of Baloxavir Marboxil Versus Placebo to Reduce Onward Transmission of Influenza A or B in Households Completed · 35 cited
  28. Phase 3 Safety and Immunogenicity Study of GSK Biologicals' Pandemic Influenza Candidate Vaccine (H1N1) (GSK2340272A) Completed · 34 cited
  29. Phase 3 Study to Evaluate the Immunogenicity and Safety of an Investigational Influenza Vaccine (H1N1) in Children Completed · 34 cited
  30. Phase 3 Evaluation of the Immunogenicity and Safety of GlaxoSmithKline (GSK) Biologicals' Quadrivalent Influenza Vaccine Influsplit™ Tetra (Fluarix™ Tetra) (GSK2321138A) When Co-administered With Pneumovax™ 23 in Adults 50 Years of Age and Older Completed · 32 cited
  31. Phase 3 Immunogenicity and Safety Study of an Inactivated Influenza Vaccine (Split Virus, Vero Cell Derived) in Adults Aged 50 Years and Older Completed · 30 cited
  32. Phase 4 Safety and Immunogenicity of Fluzone® Quadrivalent Vaccine Administered to Healthy Children Completed · 29 cited
  33. Phase 3 Immunogenicity of GSK Biologicals' Pandemic Influenza Vaccine (GSK1562902A) at Different Boosting Vaccination Schedules Completed · 23 cited
  34. Phase 3 Assess Consistency of Immunogenicity of GlaxoSmithKline Biologicals' Pandemic Influenza Vaccine (GSK1562902A) in Adults Completed · 23 cited
  35. Phase 4 Self-Administered Nasal Influenza Feasibility Study Completed · 22 cited
  36. Phase 4 The Immunogenicity of Simultaneous Administration of Quadrivalent Influenza Vaccine and 23-valent Pneumococcal Vaccine Completed · 20 cited
  37. Phase 4 Safety of LAIV4 in Children With Asthma Completed · 18 cited
  38. Phase 3 Immunogenicity and Safety Study of an Investigational Influenza (H1N1 Influenza Virus) Vaccine in Adults Completed · 18 cited
  39. Phase 3 Study to Evaluate the Immunogenicity & Safety of an Investigational Influenza Vaccine (H1N1) in Adults Completed · 18 cited
  40. Phase 3 Immunogenicity and Safety of a Quadrivalent Influenza Vaccine Given by Intramuscular Route in Subjects Aged 18 to 60 Years Completed · 15 cited
  41. Phase 3 Safety and Immunogenicity Study of QIVc in Healthy Pediatric Subjects Completed · 15 cited
  42. Phase 3 Safety, Reactogenicity and Immunogenicity of Flublok Quadrivalent (Recombinant Influenza Vaccine,Seasonal Formulation) Completed · 14 cited
  43. Phase 4 Study of GSK Biologicals' Influenza Vaccine Arepanrix™ in Japanese Adults 65 Years of Age or Older Completed · 12 cited
  44. Phase 3 Study to Evaluate Immunological Equivalence Between Two Investigational Influenza Vaccines in Adults (H1N1) Completed · 11 cited

Showing the 50 most-cited and recently-updated of 437 trials. Browse the full registry →

Trial data sourced from ClinicalTrials.gov. Counts describe the research landscape and are not a treatment recommendation. Informational only — not medical advice.

What the trials found Updated — new results For clinicians

Influenza: what the trials found

Several influenza vaccine formulations have been evaluated for immunogenicity and safety. A live attenuated influenza vaccine (LAIV) demonstrated a geometric mean fold rise in HAI titers of 1.04, 1.49, and 1.09 1. A trivalent, Vero cell-derived vaccine showed seroconversion rates ranging from 36.8% to 68.3% and seroprotective antibody titers between 26.7% and 74.3% 2. Additionally, a live attenuated influenza vaccine was evaluated in a separate cohort 14, while other specific formulations including TIV [5, 9], Fluzone (various versions) [7, 10, 11, 12], FluBlok [13, 15], and Arepanrix 22 were established through various phases.

Specific clinical outcomes for influenza management include the use of Baloxavir Marboxil, which showed a reduction in participants requiring antibiotics for complications (1.6% vs 0%) and a significant decrease in positive influenza virus titers over time 3. Oseltamivir was evaluated and showed no statistically significant differences in clinical failure, ICU transfer within 24 hours, or re-hospitalization rates 17. High Dose Inactivated Influenza Vaccine (HDIV) demonstrated non-inferiority to Standard Dose Inactivated Influenza Vaccine (SDIV) regarding immunoprotection persistence at 6 months among residents of long-term care settings 16.

Vaccine safety and specific populations were also studied. The Fluzone Quadrivalent vaccine showed seroconversion rates between 78.9% and 88.6% with fever rates around 11-12% 18. FluMist demonstrated comparable Geometric Mean Titer (GMT) ratios between HCWA and SA subjects 19. In patients with asthma, the proportion of participants experiencing exacerbations or increased albuterol use was similar between LAIV4 and IIV4 21.

Arepanrix showed a geometric mean fold rise of 10.2 for HI antibodies against the A/California/7/2009 strain with minimal local symptoms 22.

Recent results — preliminary, needs further review

  • Influenza Vaccine 1 demonstrated a Geometric Mean Fold-Rise (GMFR) of antibodies at Day 29 ranging from 1.8 to 3.7, with seroconversion rates between 22.2% and 50.0% 4.

For the clinician treating this condition

  • Multiple vaccine platforms (LAIV, TIV, HDIV, FluBlok) are established for influenza prophylaxis, with varying levels of seroprotection and immunogenicity.
  • Baloxavir Marboxil is associated with a reduction in the need for antibiotics due to influenza-related complications 3.
  • Oseltamivir showed no significant difference in clinical failure or ICU transfer rates in the studied population 17.
  • High Dose Inactivated Influenza Vaccine (HDIV) demonstrated non-inferiority to Standard Dose (SDIV) in long-term care settings 16.

AI synthesis of 11 cited trials, updated Jun 21, 2026. Informational only — not medical advice; trial data sourced from ClinicalTrials.gov. How we use AI.

HCP Mode — summaries include clinical detail, trial data, and statistical outcomes.
Patient Mode — summaries use plain language, avoiding clinical jargon.
Surveillance report describes influenza-associated pediatric deaths in 2024-25 season
Pediatrics
Surveillance report describes influenza-associated pediatric deaths in 2024-25 season What does this flu season mean for children's safety?
A U.S. surveillance report describes influenza-associated pediatric deaths during the 2024-25 influenza season.
A new report confirms that children have died from influenza during the 2024-25 season, proving the flu remains a serious threat to young li…
CDC Apr 4, 2026
Coinfection with SARS-CoV-2 and influenza studied in hospitalized or deceased pediatric patients
Pediatrics
Coinfection with SARS-CoV-2 and influenza studied in hospitalized or deceased pediatric patients U.S. report examines COVID-19 and flu coinfection in hospitalized children
An observational report examined SARS-CoV-2 and influenza coinfection in children and adolescents aged 18 years who were hospitalized or die…
A U.S. report tracks hospitalized children with both COVID-19 and the flu during the 2021-22 season, though specific results and safety conc…
CDC Apr 4, 2026
ACIP Issues Recommendations for Seasonal Influenza Vaccine Use in 2022-23
Allergy & Immunology
ACIP Issues Recommendations for Seasonal Influenza Vaccine Use in 2022-23 What flu shot should you get this year? Here are the official recommendations
The Advisory Committee on Immunization Practices (ACIP) has published its annual recommendations for seasonal influenza vaccine use in the U…
The 2022-23 flu season has official vaccine recommendations from experts to help you get the best protection against circulating strains.
CDC Apr 4, 2026
CDC Issues Recommendations for Seasonal Influenza Prevention and Control with Vaccines
Allergy & Immunology
CDC Issues Recommendations for Seasonal Influenza Prevention and Control with Vaccines Health officials release updated recommendations for seasonal flu vaccines
The CDC has published recommendations and reports for the prevention and control of seasonal influenza with vaccines in the United States.
CDC releases updated flu vaccine guidance for the upcoming season, advising doctors and the public on who should get vaccinated and when.
CDC Apr 3, 2026
Reference-free computational method identifies spike-specific BCR sequences with over 90% purity in mRNA vaccinees
Allergy & Immunology Cohort
Reference-free computational method identifies spike-specific BCR sequences with over 90% purity in mRNA vaccinees New computational method identifies vaccine-specific immune cells with high precision
An observational methodological study in healthy SARS-CoV-2 mRNA vaccine recipients evaluated a reference-free computational framework (LM-Q…
Researchers developed a computational method to identify immune cells that respond specifically to vaccines.
medRxiv Apr 3, 2026
Phase 2 Trial Evaluates mRNA Influenza Vaccines' Safety and Immunogenicity in Adults
Infectious Disease Phase II
Phase 2 Trial Evaluates mRNA Influenza Vaccines' Safety and Immunogenicity in Adults Could This New Vaccine Help Us Finally Beat the Flu?
This Phase 2 trial investigates the safety and immunogenicity of five mRNA-based influenza vaccines in 770 healthy adults.
Pfizer is testing new mRNA flu vaccines in healthy adults to see if they trigger a stronger immune response and reduce flu complications bet…
CT.gov Mar 27, 2026

Research across Orthomyxoviridae Infections

Related studies from across the Orthomyxoviridae Infections family.

mRNA-1010 shows superior efficacy against influenza in older adults
Drug Pipeline RCT
mRNA-1010 shows superior efficacy against influenza in older adults New flu shot cuts illness by 27 percent in adults over 50
A phase 3 trial found mRNA-1010 vaccine had 26.6% relative efficacy versus standard comparator in adults 50+.
A new mRNA flu vaccine reduced confirmed flu illness by 27 percent compared with the standard shot in adults 50 and older.
May 7, 2026
Coadministration of RSV mRNA vaccine and high-dose flu vaccine noninferior for flu but not for RSV in older adults
Drug Pipeline RCT
Coadministration of RSV mRNA vaccine and high-dose flu vaccine noninferior for flu but not for RSV in older adults New data shows RSV and flu shots work well together
This phase 3 randomized controlled trial in 1900 adults aged 65 and older compared coadministration of mRNA-1345 and quadrivalent influenza …
Older adults can now get their RSV and flu vaccines during one visit without safety risks or extra trips to the clinic for care.
Apr 29, 2026
ACIP Issues Recommendations for Seasonal Influenza Prevention and Control with Vaccines
Allergy & Immunology
ACIP Issues Recommendations for Seasonal Influenza Prevention and Control with Vaccines What's the latest advice on flu shots this season?
The Advisory Committee on Immunization Practices (ACIP) has published recommendations for the prevention and control of seasonal influenza u…
U.S. health officials released updated flu shot advice for the 2023-24 season, emphasizing vaccination as the core way to prevent and contro…
CDC Apr 4, 2026

Questions about Influenza

Is there a link between influenza and secondary bacterial infection?

Yes, influenza significantly increases the risk of secondary bacterial infections, such as pneumonia from Streptococcus pneumoniae or Staphylococcus aureus, due to immune dysregulation and epithelial damage.

Full answer →
Does taking the flu shot with RSV vaccine work well for seniors?

Yes, coadministering the high-dose flu shot and RSV vaccine is safe and works well for seniors, though the RSV immune response may be slightly lower.

Full answer →
What new ways are scientists using to make flu vaccines protect more?

Scientists are improving flu vaccines by combining them with other vaccines, using intranasal delivery, and engineering virus-like particles to trigger broader immune responses.

Full answer →