What this study is
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:
- MK-1406 (formerly CD388) is safe to take with Fluzone®
- MK-1406 affects the immune response to Fluzone®
What's being tested
- Fluzone® High-Dose (HD) influenza vaccine
Intervention · BIOLOGICAL
Fluzone® HD injectable suspension administered by intramuscular (IM) injection
- MK-1406 Injection
Intervention · COMBINATION PRODUCT
MK-1406 liquid for injection administered subcutaneously
- Placebo
Intervention · COMBINATION PRODUCT
MK-1406 matched liquid for SC injection
Study details
- Official title
- A Phase 1, Double-blind, Randomized Trial to Evaluate Safety and Immunogenicity of Fluzone® High-Dose Influenza Vaccine When Concomitantly Administered With CD388, a Novel Long-Acting Antiviral Conjugate for the Prevention of Influenza
- Sponsor
- Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)
- Conditions
- Healthy Participants
- Enrolling
- 710 people
- Starts
- 2025-11-08
- Est. completion
- 2026-12-31
- Design
- Quadruple-blind, randomized, parallel groups, Phase 1
- Record
- View on ClinicalTrials.gov ↗
Who can join
Age 18 Years – 49 YearsSex ALLHealthy volunteers AcceptedYou may qualify if
- Be ≥18 to ≤49 years of age
- Be deemed healthy by the Investigator
- Have not received any seasonal influenza vaccine and have not had a diagnosed or suspected influenza infection within 12 months prior to Day 1 of the trial
You can't join if
- Had an active malignancy within 5 years prior to screening, except basal cell or squamous cell skin cancer. Any history of breast cancer or melanoma is exclusionary.
- Has previously been diagnosed with Guillain-Barre Syndrome following a previous influenza vaccination.
Sign in and we'll check these against your records.Full criteria on ClinicalTrials.gov ↗
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Study locations (2)
2 open- Recruiting
- Recruiting
Study team
Sponsor
Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA)
Study ID 1406-007
Study director
Medical Director
Merck Sharp & Dohme LLC
Frequently asked questions
The sponsor hasn't published answers to common questions for this trial.