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Home › Conditions › Diphtheria

Diphtheria

3 published articles · Updated continuously

Clinical Trial Landscape

Clinical Trials for Diphtheria

106 trials tracked for Diphtheria: 89 in phase 3 or 4 and 20 with published results. The most-cited published study has 96 citations.

106Trials tracked
89Phase 3 & 4
0Recruiting
20With published results
Phase distribution
Phase 4 31 Phase 3 58 Phase 2 12 Phase 1 2 Other / NA 3
  1. Phase 4 Immunogenicity & Reactogenicity of Boostrix 10 Years After Previous Booster Vaccination. Completed · 96 cited
  2. Phase 4 Immunogenicity & Reactogenicity of Boostrix 10 Years After Previous Booster Vaccination in Study NCT01267058 Completed · 65 cited
  3. Phase 3 Immunogenicity, Safety of GSKs Tdap Vaccine Boostrix When Coadministered With GSKs Influenza Vaccine Fluarix in Adults Completed · 63 cited
  4. Phase 3 Safety and Immunogenicity of GSK's Tdap Vaccine (Boostrix) in Adults Aged 19 to 64 Years Completed · 57 cited
  5. Phase 4 Safety and Immunogenicity in Adults of Revaccination With Adacel® Vaccine 10 Years After a Previous Dose Completed · 38 cited
  6. Phase 4 Immunogenicity and Safety Study of Infanrix Hexa in Healthy Infants Born to Mothers Vaccinated With Boostrix™ During Pregnancy or Immediately Post-delivery Completed · 29 cited
Show 44 more trials
  1. Phase 4 US-licensed Combined Vaccine Against Tetanus & Diphtheria, Given With US-licensed Vaccine Against Meningococcal Disease Completed · 28 cited
  2. Phase 4 Safety and Immunogenicity of a Booster Dose of GSK Biological's Boostrix-Polio Vaccine Completed · 26 cited
  3. Phase 3 Immunogenicity and Safety of Boostrix Polio Vaccine as a Booster Dose in 5 to 6-year-old Children. Completed · 19 cited
  4. Phase 3 Non-inferiority of GSK Biologicals' DTPw-HBV/Hib Compared to Two Formulations of GSK Biologicals' DTPw-HBV/Hib Completed · 18 cited
  5. Phase 3 Immunogenicity and Safety of GSK Biologicals' Boostrix Polio Vaccine in 3 and 4-year-old Children Completed · 16 cited
  6. Phase 3 Immunogenicity and Safety Study of Proquad® and Infanrix® Hexa When Administered Concomitantly (V221-035) Completed · 13 cited
  7. Phase 4 Evaluation of Immunogenicity and Safety of a Booster Dose of Infanrix Hexa™ in Healthy Infants Born to Mothers Vaccinated With Boostrix™ During Pregnancy or Immediately Post-delivery Completed · 12 cited
  8. Phase 4 Immunogenicity and Safety of Booster Dose of BoostrixTM Polio Vaccine in Previously Boosted Adults Completed · 12 cited
  9. Phase 4 Immunogenicity and Safety of GSK Biologicals' Infanrix Hexa in Infants Completed · 10 cited
  10. Phase 3 A Study to Assess the Immunogenicity and Safety of GSK Biologicals' Infanrix-IPV/Hib Vaccine Administered as a Three-dose Vaccination Course at 3, 4.5 and 6 Months of Age and a Booster Dose at 18 Months of Age in Healthy Infants in Russia Completed · 6 cited
  11. Phase 4 Regulatory Post-Marketing Surveillance Study for TETRAXIM™ Completed · 5 cited
  12. Phase 4 Study of Adacel® Vaccine Administered to Persons 10 Years of Age Completed · 5 cited
  13. Phase 3 Confirmatory Study of BK1310 in Healthy Infants Completed · 1 cited
  14. Phase 4 Immunogenicity and Safety of BoostrixTM Using a New Syringe in 10 to 15-year Old Adolescents Completed
  15. Phase 4 Study to Evaluate Antibody Persistence in Children Previously Vaccinated With Infanrix Hexa™ or Infanrix-IPV/Hib™ Completed
  16. Phase 4 Post Marketing Surveillance for ADACEL™ in South Korea Completed
  17. Phase 4 Assess the Safety & Reactogenicity of DTPa-IPV/Hib Vaccine Administered at 3, 4, 5 & 18 Mths of Age, in Healthy Infants Completed
  18. Phase 4 Tdap Vaccine in Post-Partum Women Completed
  19. Phase 4 A Study to Evaluate Immunogenicity and Safety of GlaxoSmithKline (GSK)'s Infanrix Hexa Vaccine (DTPa-HBV-IPV/Hib) Versus MCM Vaccine BV's Vaxelis Vaccine (DTaP5-HBV-IPV-Hib) in Healthy Infants and Toddlers Completed
  20. Phase 4 PFAS Exposure and Immune Response to Vaccination in Adults Completed
  21. Phase 4 Post-licensure, Modified Double-blind, Multi-center Study Evaluating Safety and Immunogenicity of ADACEL® and BOOSTRIX® Completed
  22. Phase 4 Evaluation of Boostrix™10 Years After Previous Booster Vaccination Completed
  23. Phase 4 A Trial to Evaluate the Safety and Immunogenicity of ADACEL® Vaccine in Persons 65 Years of Age and Older Completed
  24. Phase 4 Canadian Manufactured Tetanus and Diphtheria Toxoids Adsorbed (Td) Vaccine Compared With U.S. Manufactured Td Completed
  25. Phase 4 Study to Assess if Quinvaxem Can be Interchanged With Other Pentavalent Vaccines During Standard Childhood Vaccination Completed
  26. Phase 4 Descriptive, Open-label, Multicenter Study of the Safety of Redosing With ADACEL® Vaccine Completed
  27. Phase 4 Study of Menactra® in Healthy Subjects at 9 Months and Concomitantly With Pentacel® at 15 to 18 Months of Age Completed
  28. Phase 4 Immunogenicity of Adacel® and BOOSTRIX® Vaccines in Adolescents Completed
  29. Phase 4 Study of DAPTACEL® Administered as a 5th Dose in 4 to 6-Year-Old Children Previously Immunized With PENTACEL™ Completed
  30. Phase 4 Immune Responses in Adults to Revaccination With ADACEL® 10 Years After a Previous Dose Completed
  31. Phase 4 Study of Menactra® in US Adolescents When Administered Concomitantly With Tdap Vaccine Completed
  32. Phase 4 Post-marketing Evaluation of Reactions Following Receipt of Recommended Adolescent Pertussis Vaccine Completed
  33. Phase 4 Study of a New Formulation of DTPa-HBV-IPV/Hib Vaccine Administered as a Booster Dose to 18-23 Months Old Children Completed
  34. Phase 3 Study of BK1301 (DTaP Vaccine) as a Booster in Adolescents Completed
  35. Phase 3 Safety of a Booster Dose of GlaxoSmithKline (GSK) Biologicals' Boostrix™ Vaccine in Healthy Vietnamese Children Completed
  36. Phase 3 Safety of DTPa-IPV/Hib & DTPa-HBV-IPV/Hib, Followed by DTPa-IPV/Hib Vaccine in Infants Who Received Hepatitis B Vaccine Completed
  37. Phase 3 Study to Assess Safety & Immunogenicity of GSK Biologicals' DTPa/Hib Vaccine vs Separate Administration of DTPa and Hib. Completed
  38. Phase 3 Immune Memory of DTPw-HBV/Hib Vaccine Following Primary Vaccination, Immuno & Reacto of a Booster Dose Given in Infants Completed
  39. Phase 3 Safety Study of Tritanrix-HepB/Hib-MenAC, Tritanrix-HepB/Hiberix, and Mencevax ACWY Vaccines in Children Completed
  40. Phase 3 Safety Study of GSK Biologicals' DTPa-IPV/Hib (Infanrix™-IPV/Hib) Completed
  41. Phase 3 Immunogenicity and Safety Study of GSK Biologicals' Infanrix-IPV+Hib™ Vaccine Completed
  42. Phase 3 Immunogenicity and Safety Study of Booster Dose of GSK Biologicals' IPV (Poliorix™) and DTPa/Hib (Infanrix+Hib™) Vaccine Completed
  43. Phase 3 Immunogenicity and Safety of GlaxoSmithKline (GSK) Biologicals' Boostrix™ Vaccine in Previously Boosted Young Adults Completed
  44. Phase 3 Study to Determine the Immunogenicity and Safety of GlaxoSmithKline (GSK) Biologicals; Infanrix Hexa at 2, 4 and 6 Months of Age in Healthy Infants Completed

Showing the 50 most-cited and recently-updated of 106 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

Diphtheria: what the trials found

Multiple Tdap vaccines (Boostrix, Adacel) demonstrate high seroprotection rates against diphtheria, with anti-diphtheria antibody concentrations ≥0.1 IU/mL achieved in the majority of recipients 3412. Seroprotection rates of 99-100% were observed for diphtheria and tetanus following Tdap vaccination 412. Booster responses to diphtheria were also high, ranging from 74.5% to 84.1% across different age groups 4. Ten years after a previous dose, revaccination with Adacel restored seroprotection to 100% for both tetanus and diphtheria 20.

Local and systemic reactions are common but generally mild. Solicited local symptoms (e.g., pain, swelling) occurred in 76-80.9% of subjects after Boostrix or Adacel, with grade 3 events in 2-8% 23612. Solicited general symptoms (e.g., fatigue, headache) were reported in 39.4-44% of subjects, with grade 3 events in 0-2% 2312. Unsolicited adverse events were also reported but were mostly mild to moderate 6. Concomitant administration of Tdap with other vaccines (e.g., Menactra, Pentacel) did not compromise immune responses to diphtheria, tetanus, or pertussis antigens 19.

A new trial (NCT06588530) found that TENIVAC produced a change in tetanus-diphtheria specific IgG by PFNA exposure category (3.54, 3.39, 2.44, 2.43; p=.85), indicating no significant difference across exposure groups 1.

Recent results — preliminary, needs further review

  • A phase 4 trial (NCT06588530) evaluated TENIVAC and found no significant difference in tetanus-diphtheria IgG change across PFNA exposure categories (p=.85), but this finding is from a single small study (N=20) and requires further corroboration 1.

For the clinician treating this condition

  • Tdap vaccines (Boostrix, Adacel) reliably induce seroprotection against diphtheria in the vast majority of recipients, with booster responses also high.
  • Local and systemic reactions are common but generally mild and self-limited; grade 3 events are infrequent.
  • Revaccination with Tdap 10 years after a prior dose effectively restores seroprotection to 100%.

AI synthesis of 8 cited trials, updated Jun 25, 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.
ACIP updates adult vaccination recommendations, allowing Tdap or Td in more scenarios
Allergy & Immunology
ACIP updates adult vaccination recommendations, allowing Tdap or Td in more scenarios New vaccine rules give adults more options for tetanus and whooping cough protection
The Advisory Committee on Immunization Practices has updated recommendations for adult vaccination in the United States.
Adults in the U.S. now have more options for their tetanus shots, as health advisors say both Tdap and Td vaccines are acceptable for routin…
CDC Apr 4, 2026
Influenza and Tdap vaccination coverage among pregnant women in the United States
OB/GYN & Women's Health
Influenza and Tdap vaccination coverage among pregnant women in the United States Report examines flu and whooping cough vaccination rates in pregnant women
An observational report describes influenza and Tdap vaccination coverage among pregnant women in the United States.
A new report examines flu and whooping cough vaccination rates for pregnant women during the 2019-20 season, highlighting the need for more …
CDC Apr 4, 2026
New 6-in-1 infant vaccine licensed but availability delayed until at least 2021
Gastroenterology
New 6-in-1 infant vaccine licensed but availability delayed until at least 2021 New six-in-one vaccine for infants receives regulatory approval
A new combination vaccine for infants targeting diphtheria, tetanus, pertussis, polio, Hib, and hepatitis B has received licensure.
A new six-in-one vaccine for infants has received regulatory approval, but it won't be available for use until 2021 or later.
CDC Apr 3, 2026

Questions about Diphtheria

Why was the new diphtheria-containing infant vaccine delayed until at least 2021?

A new combination vaccine that includes protection against diphtheria was licensed but could not be available to infants until at least 2021 due to supply and timing delays.

Full answer →