Largest late-stage clinical trials by enrollment

Name: Largest late-stage clinical trials by enrollment
Creator: AIDb
License: https://clinicaltrials.gov/about-site/terms-conditions

The 1,000 Phase 3 and Phase 4 interventional trials on ClinicalTrials.gov with the most participants, actual or planned — mass drug-administration, vaccine and screening trials among them. One row per trial, with its conditions, phase, status, start date, enrollment and type of sponsor.

1,000 rows10 columns Updated 6 h ago Facts (not copyrightable) — source credited

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NCT number

Study

Conditions

Phase

Status

Start

Enrollment

Enrollment type

NCT06358872

Azithromycin for Child Survival in Niger II

Phase 4

Recruiting

Apr 29, 2024

3,300,000

Estimated

NCT04224987

Azithromycin for Child Survival in Niger: Mortality and Resistance Trial

Phase 4

Completed

Nov 24, 2020

864,493

Actual

NCT00222547

Deworming and Enhanced Vitamin A Every 6 Month in Rural Indian Children Aged 1-6

Phase 4

Completed

Jan 1999

720,000

NCT04716712

Infant Mortality Reduction by the Mass Administration of Azithromycin

Phase 4

Active not recruiting

Oct 4, 2021

694,400

Estimated

NCT06684743

Vaccine Effectiveness of a Bivalent RSV Prefusion F Protein-Based Vaccine for Preventing RSV Hospitalizations in Adults

Respiratory Tract Diseases

Phase 4

Active not recruiting

Nov 18, 2024

690,000

Estimated

NCT05148845

Sisonke 2 - A COVID-19 Vaccine Boost Open Label Study.

COVID-19

Phase 3

Completed

Nov 10, 2021

500,000

Actual

NCT04838795

Sisonke (Together): OPEN LABEL TRIAL COVID-19

Severe Acute Respiratory Syndrome

Phase 3

Completed

Feb 17, 2021

477,102

Actual

NCT06506812

Pooled Analysis of Methodologically Harmonized Pragmatic Randomized Trials of High-Dose vs. Standard-Dose Influenza Vaccine Against Severe Clinical Outcomes

Influenza, Human; Pneumonia

Phase 4

Completed

May 31, 2025

466,320

Actual

NCT07790523

Effectiveness of An Influenza/COVID-19 Vaccine (mCombriax [mRNA-1083]) in Adults ≥ 65 Years

COVID-19; Influenza, Human; Respiratory Tract Diseases

Phase 4

Not yet recruiting

Sep 1, 2026

410,000

Estimated

NCT06934239

A Trial Comparing Screening Mammography With and Without Assistance From Artificial Intelligence for Breast Cancer Detection and Recall Rates in Adult Patients

Phase 4

Recruiting

Oct 15, 2025

400,000

Estimated

NCT02556242

Targeted Indoor Residual Spraying Against Malaria

Malaria

Phase 4

Completed

Oct 2015

393,387

Actual

NCT03014167

Field Studies on the Feasibility of Interrupting the Transmission of Soil-transmitted Helminths (STH)

Helminthiasis; Filariasis

Phase 3

Completed

Oct 4, 2017

357,716

Actual

NCT03140423

Mupirocin-Iodophor ICU Decolonization Swap Out Trial

Staphylococcal Infections; Cross Infection

Phase 4

Completed

May 1, 2017

353,323

Actual

NCT05517174

A Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Older Adults

Influenza, Human; Pneumonia

Phase 4

Completed

Sep 22, 2022

332,438

Actual

NCT03335072

Kebele Elimination of Trachoma for Ocular Health

Trachoma

Phase 4

Active not recruiting

Feb 7, 2022

320,000

Estimated

NCT04177043

Model Towards Elimination of Hepatitis C Infection in Egypt: Feasibility and Effectiveness in 73 Villages

Hepatitis C, Chronic

Phase 4

Completed

Jun 2015

221,855

Actual

NCT02027207

Single Dose Oral Cholera Vaccine Study in Dhaka, Bangladesh

Cholera

Phase 3

Completed

Dec 9, 2012

204,438

Actual

NCT00203749

Community Mobilization, Mobile Testing, Same-Day Results, and Post-Test Support for HIV in Sub-Saharan Africa and Thailand

HIV Infections

Phase 3

Completed

Dec 2004

192,814

Actual

NCT02047981

Mortality Reduction After Oral Azithromycin: Mortality Study

Infections

Phase 4

Completed

Dec 2014

190,238

Actual

NCT05288023

Azithromycin for Child Survival in Niger: Programmatic Trial (AVENIR)

Phase 4

Terminated

Dec 1, 2022

169,707

Actual

NCT07485283

Recombinant Herpes Zoster Vaccine for Prevention of Cardiovascular Events and Dementia

Cardiovascular Diseases; Dementia; Herpes Zoster

Phase 4

Active not recruiting

Apr 28, 2026

168,460

Actual

NCT02079701

Effectiveness of the Pneumococcal Polysaccharide Vaccine in Military Recruits

Pneumonia

Phase 4

Completed

Oct 2000

152,723

Actual

NCT07314307

Vaccine Effectiveness of One Dose of the Nonavalent Human Papillomavirus (HPV) Vaccine Among Young-adult Women in Sweden Among Women Participating in a Clinical Trial of Concomitant HPV Vaccination and Screening

Phase 4

Active not recruiting

May 3, 2021

150,000

Estimated

NCT04910802

Concomitant HPV Vaccination and HPV Screening HPV Infection and Cervical Cancer in Sweden

Papillomavirus Infections; Uterine Cervical Neoplasms

Phase 4

Recruiting

May 3, 2021

150,000

Estimated

NCT04424511

Effects of Mass Drug Administration of Azithromycin on Mortality and Other Outcomes Among 1-11 Month Old Infants in Mali

Inflammation; Infections

Phase 3

Completed

Oct 15, 2020

149,201

Actual

NCT03662022

Post ExpOsure Prophylaxis for LEprosy in the Comoros and Madagascar

Leprosy

Phase 3

Completed

Jan 2, 2019

144,000

Actual

NCT06141655

HD vs SD Quadrivalent Influenza Vaccine in Adults Aged 65 to 79 Years in Galicia

Influenza, Human

Phase 4

Completed

Oct 26, 2023

134,476

Actual

NCT04911790

Safety of an Inactivated SARS-CoV-2 Vaccine for Prevention of COVID-19 in Adults

COVID-19

Phase 4

Completed

Jun 5, 2021

131,650

Actual

NCT06719193

DeMONSTRATE-TB Study in Ethiopia

Phase 2, Phase 3

Recruiting

Feb 27, 2023

131,438

Estimated

NCT05597280

Bedaquiline Enhanced Post ExpOsure Prophylaxis for Leprosy

Leprosy

Phase 3

Recruiting

Mar 22, 2023

124,000

Estimated

NCT01014845

Clinical Trial of Recombinant Hepatitis E Vaccine

Hepatitis E

Phase 3

Completed

Aug 2007

112,604

Actual

NCT03233191

Digital Tomosynthesis Mammography and Digital Mammography in Screening Patients for Breast Cancer

Phase 3

Active not recruiting

Sep 28, 2017

108,508

Estimated

NCT00131820

Introduction of the Vi Polysaccharide Typhoid Vaccine in Hue City, Central Vietnam

Typhoid Fever; Paratyphoid Fever

Phase 4

Completed

Dec 2001

100,742

NCT00211341

Trial of the Impact of Vitamin A on Maternal Mortality

Vitamin A Deficiency; Maternal Death

Phase 3

Completed

Dec 2000

100,000

Estimated

NCT06536855

Faster Elimination of HPV Infection and Cervical Cancer Using Concomitant HPV Vaccination and HPV Screening: A Demonstration Project in Rwanda

Uterine Cervical Neoplasms

Phase 4

Unknown

Sep 1, 2024

100,000

Estimated

NCT05890521

Safety Study of COVID19 Vaccine on the Market

COVID-19

Phase 4

Unknown

Apr 2, 2022

100,000

Estimated

NCT04353180

Assessment the Activity Value of Isotretinoin (13- Cis-Retinoic Acid ) in the Treatment of COVID-19 ( Isotretinoin in Treatment of COVID-19) (Randomized)

COVID-19

Phase 3

Unknown

Aug 2021

100,000

Estimated

NCT00712374

Evaluation of the Public Health Impact of Seasonal Intermittent Preventive Treatment (IPT) in Children in Senegal

Malaria

Phase 4

Unknown

Sep 2008

100,000

Estimated

NCT03909737

Oral Azithromycin to Prevent Stillbirths and Infant Mortality in Mali

Stillbirth; Infant Death

Phase 4

Active not recruiting

Sep 24, 2020

99,700

Actual

NCT00131833

Typhoid Vi Vaccine Effectiveness in Hechi, Guangxi, China

Typhoid Fever; Paratyphoid Fever

Phase 4

Completed

Oct 2001

96,468

NCT00883792

The Northern-European Initiative on Colorectal Cancer

Colorectal Neoplasms

Phase 3

Active not recruiting

May 2009

95,000

Actual

NCT02590315

Tomosynthesis Versus Digital Mammography in a Population-based Screening Program

Breast Neoplasms

Phase 4

Unknown

Dec 2014

92,000

Estimated

NCT01528449

Babesia Testing in Blood Donors

Phase 3

Completed

Dec 2011

90,116

Actual

NCT02987270

Evaluation of Community-based Mass Screening and Treatment for Malaria in Western Kenya

Malaria, Falciparum; Malaria; Asymptomatic Infections

Phase 3

Completed

Apr 2013

90,000

Actual

NCT00744263

Study Evaluating the Effiacy of a 13-Valent Pneumococcal Conjugate Vaccine (13vPnC) in Adults

Pneumonia, Pneumococcal; Pneumococcal Infections

Phase 4

Completed

Sep 2008

84,496

Actual

NCT00222664

Qidong Hepatitis B Intervention Study

Hepatitis B; Liver Neoplasms; Liver Diseases

Phase 4

Completed

Sep 1983

80,000

NCT07177352

Screening Study to Determine Individuals With Potential Trial Eligibility for Alzheimer's Disease Studies

Alzheimer Disease; Cognitive Dysfunction

Phase 3

Recruiting

Jul 2, 2025

80,000

Estimated

NCT03923699

Telemedicine Control Tower for the Operating Room: Navigating Information, Care and Safety

Postoperative Complications

Phase 3

Completed

Jul 1, 2019

79,560

Actual

NCT03676764

Community Health Azithromycin Trial in Burkina Faso

Phase 4

Completed

Aug 1, 2019

77,664

Actual

NCT01241318

Zambia Chlorhexidine Application Trial

Sepsis

Phase 2, Phase 3

Completed

Feb 2011

77,535

Actual

Columns

Stable keys — use them in the API, SQL and code

Key	Name	Type	Description
nct_id	NCT number	string	ClinicalTrials.gov identifier.
title	Study	string	Brief title as registered.
conditions	Conditions	string	Up to three MeSH condition terms.
phase	Phase	string	—
status	Status	string	Recruitment status at the time of the build.
start_date	Start	date	Start date (actual or planned).
enrollment	Enrollment	integer	Number of participants, actual or planned.
enrollment_type	Enrollment type	string	Actual or Estimated.
sponsor_type	Sponsor type	string	Industry, NIH, U.S. federal, other government, network, or university/hospital/nonprofit.
url	Record	url	—

About this data

Source: ClinicalTrials.gov API v2 — U.S. National Library of Medicine
License: Facts (not copyrightable) — source credited
Required attribution: Data from ClinicalTrials.gov, U.S. National Library of Medicine (clinicaltrials.gov), aggregated by AIDB.
Updated: Oct 29, 2026 13:22 UTC
Refresh: monthly
Rows: 1,000
Size (JSON): 262 KB
Notes: Limited to interventional studies labelled Phase 3 or Phase 4 (including combined Phase 2/3), the late-stage trials that test treatments and vaccines at scale; earlier-phase and 'not applicable' studies are left out because their registered enrollment figures are often placeholders. Enrollment is the number of participants as registered by the sponsor: 'Actual' once enrollment is complete, 'Estimated' (planned) for studies that are still recruiting or have not started. Some of the largest are cluster-randomised community trials (e.g. mass azithromycin distribution) in which whole populations are counted. Conditions are the MeSH terms ClinicalTrials.gov matches to the study (up to three shown). Sponsor names are not included because many studies list an individual investigator as sponsor; the sponsor type is shown instead.

Cite this dataset

AIDb. (2026). Largest late-stage clinical trials by enrollment [Data set]. ClinicalTrials.gov API v2 — U.S. National Library of Medicine. https://aidb.si/d/largest-clinical-trials

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