A Phase 1 interventional study of Fluzone® High-Dose (HD) influenza vaccine and MK-1406 Injection in Healthy Participants, sponsored by Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA). Recruiting at 2 sites in United States. Open to participants aged 18 Years to 49 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-04.
Sponsored by Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) (part of Merck & Co., Inc) · Phase 1, Interventional, and Prevention
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Among 966 studies in Influenza, Human with a site in United States — 60 open to participants now, 85 under way, 7 of them phase 3. Influenza, Human · United States.
Among the 966 studies in Influenza, Human with a site in United States, this one is the 249th largest by planned enrollment of the 843 interventional ones that give a count, is one of 29 that started in 2025, is one of 177 in phase 1, reaches primary completion later than 19 of the 83 other live ones, and was the 944th registered.
2,358 studies on the registry are indexed under Influenza, Human; 184 are open to participants now.
Browse Influenza, Human studies →60 of the 966 studies in Influenza, Human with a site in United States are open now. Recruiting first, the newest first:
National Institute of Allergy and Infectious Diseases (NIAID) · Sites in United States
Ages 18–55 · Healthy volunteers
ModernaTX, Inc. · Sites in United States
Ages 65+ · Healthy volunteers
ModernaTX, Inc. · Sites in United States
Ages 9–17 · Healthy volunteers
National Institute on Deafness and Other Communication Disorders (NIDCD) · Sites in United States
Ages 18–99 · Healthy volunteers
David Moss · Sites in United States
Ages 18+ · Healthy volunteers
A study can be open while its sites in United States have not opened yet or have stopped. Only those recruiting at a site in United States →
Of the 121 Influenza, Human studies recruiting now, 66 (55%) set no upper age limit and 45 (37%) stop at 75 or younger; 33 take children under 18; 67 take healthy volunteers.
This study: 18 Years to 49 Years · all sexes · healthy volunteers too.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
966 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 249 · Phase 2 244 · Phase 3 127 · Phase 4 147
First in 1997; this study’s year is marked. 29 started in 2025.
By drug class, each counting the studies that test any of its medicines:
This study's planned enrollment of 710 is above the median of 227 across 1,957 interventional studies indexed under Influenza, Human.
Median enrollment 270 across the 843 interventional studies, 261 across the 122 observational. Of the 841 that completed or were terminated, 433 (51%) have results posted.
This tab as a report to print or save as PDF → With an account.
435 of 966 have an industry lead sponsor. The 10 most frequent:
This study is registered under Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA), one of the names counted as Merck & Co., Inc. Under that name alone:
Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) is the lead sponsor of 4 studies on the registry; 2 are open to participants now.
Merck & Co., Inc has 7 studies filed under Influenza, Human — fewer than ten, so there is no comparison to draw.
41 of the studies in Influenza, Human with a site in United States that are under way reach primary completion within a year, 5 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT07496450Phase 3ModernaTX, Inc.A Study of mRNA-1018-H5 Pandemic Influenza Vaccine in Healthy Adults | 2027-01-28 |
| NCT06094010Phase 3Hoffmann-La RocheA Surveillance Study of Susceptibility to Baloxavir Marboxil in Pediatric Participants With Influenza and Transmission of Influenza to Household Contacts | 2027-05-11 |
| NCT07159763Phase 3Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)A Study to Evaluate the Safety and Efficacy of MK-1406/CD388 for Prevention of Influenza (MK-1406-005/CD388.SQ.3.06) | 2027-07-02 |
| NCT07851246Phase 3GlaxoSmithKlineA Study to Evaluate the Immune Response and Safety of a Vaccine Against Influenza in Adults 18-64 Years of Age | 2027-07-09 |
| NCT05624450Phase 3AstraZenecaEfficacy and Safety of Tozorakimab in Patients Hospitalised for Viral Lung Infection Requiring Supplemental Oxygen | 2027-11-04 |
Add all 41 to your calendar (.ics) → With an account.
Among the 966 studies in Influenza, Human with a site in United States, from their registry updates:
This tab as a report to print or save as PDF → With an account.
Approximately one billion cases of seasonal influenza occur annually. Of these, 3 to 5 million illnesses are severe and responsible for up to 650,000 deaths per year (WHO 2025). Yearly administration of an influenza vaccine for the prevention of influenza is currently recommended. However, the real-world vaccine effectiveness varied from 10% to 60% in the general population across the years of 2004 to 2024, with effectiveness in most years below 50% (CDC 2025) and decreasing to as low as 5% in immunocompromised individuals (Hughes 2021). Researchers are looking for other ways to prevent severe illness from the influenza virus.
The goals of this study are to learn if:
This is a Phase 1, double-blind, randomized trial to evaluate the immunogenicity of Fluzone® HD influenza vaccine when concomitantly administered with either MK-1406 or placebo, in healthy participants. This study will also evaluate the safety and tolerability of MK-1406 when administered with Fluzone® High-Dose (HD) compared to Fluzone® HD with placebo.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
The main inclusion criteria include but are not limited to the following:
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive open-label Fluzone® HD influenza vaccine by intramuscular (IM) injection plus MK-1406 by subcutaneous (SC) injection on Day 1.
Biological: Fluzone® High-Dose (HD) influenza vaccine · Combination Product: MK-1406 Injection
Participants will receive open-label Fluzone® HD influenza vaccine by IM injection plus placebo by SC injection on Day 1.
Biological: Fluzone® High-Dose (HD) influenza vaccine · Combination Product: Placebo
Fluzone® HD injectable suspension administered by intramuscular (IM) injection
Also known as: Fluzone® High-Dose Influenza Vaccine
MK-1406 liquid for injection administered subcutaneously
Also known as: CD388
MK-1406 matched liquid for SC injection
Geometric Mean of Hemagglutinin Inhibition (HAI) Titers Against the Influenza Strains Contained in the Vaccine Among Participants Receiving Concomitant Fluzone® High-Dose (HD) and MK-1406 Compared to Participants Who Receive Fluzone® HD and Placebo
Geometric mean of HAI titers at 2-weeks and 4-weeks post-trial intervention against the influenza virus strains contained in the vaccine among participants receiving concomitant Fluzone® HD influenza vaccine and MK-1406 compared to participants who receive Fluzone® HD and placebo will be determined. HAI testing will be performed using validated methods in accordance with applicable Good Clinical Laboratory Practice (GCLP) and laboratory Standard Operating Procedures (SOPs). Geometric Mean Titers (GMTs) will be summarized by treatment group and influenza strain.
Time frame: Predose (Day 1), Day 15 and Day 29
Percentage of Participants with Seroconversion Rates against the Influenza Strains Contained in the Vaccine Among Participants Receiving Concomitant Fluzone® HD and MK-1406 Compared to Participants Who Receive Fluzone® HD and Placebo
Seroconversion is defined as a 4-fold increase in influenza titer as measured by HAI assay at each visit compared to baseline. Seroconversion rates at 2-weeks and 4-weeks post-trial intervention against the influenza virus strains contained in the vaccine among participants receiving concomitant Fluzone® HD influenza vaccine and MK-1406 compared to participants who receive Fluzone® HD and placebo will be determined. Seroconversion rates will be summarized by treatment group and influenza strain.
Time frame: Predose (Day 1), Day 15 and Day 29
Percentage of participants with ≥1 Adverse Event (AE)
An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product temporally associated with the use of study treatment, whether or not considered related to the study treatment.
Time frame: Up to approximately Day 29
Percentage of Participants Who Discontinued from the Study Due to an Adverse Event
An AE is defined as any untoward medical occurrence in a participant administered a pharmaceutical product temporally associated with the use of study treatment, whether or not considered related to the study treatment. The percentage of participants who discontinued the study because of an AE (as defined above) will be assessed.
Time frame: Up to approximately Day 29
Percentage of Participants with a Solicited Injection-site Adverse Event
An AE is any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The solicited injection-site AEs assessed are redness/erythema, swelling, and tenderness/pain.
Time frame: Up to approximately Day 8 post-dose
Percentage of Participants with a Solicited Systemic Adverse Event
An AE is any untoward medical occurrence in a patient or clinical study participant, temporally associated with the use of study treatment, whether or not considered related to the study treatment. The solicited systemic AEs assessed are muscle pain/myalgia, joint pain/arthralgia, headache, and tiredness/fatigue.
Time frame: Up to approximately Day 29
Plan to share: Yes — https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
Data sharing details ↗ · externaldatasharing-msd.com
Started Nov 2025 (actual). Primary completion is estimated for Dec 2026, 13 months after the start.
Of 94 industry-sponsored phase 1 interventional studies under Influenza, Human, half reached primary completion within 9 months of starting (the median), counting those still running; a quarter within 4 and three quarters within 16. This study's planned 13 months is above that.
Counting every sponsor, half of 148 studies reached it within 11 months; a quarter within 4 and three quarters within 21.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: MK-1406
Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) →