Fluzone® High-Dose (HD) influenza vaccine: Fluzone® HD injectable suspension administered by intramuscular (IM) injection
MK-1406 Injection: MK-1406 liquid for injection administered subcutaneously
Placebo: MK-1406 matched liquid for SC injection
Study summary
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®
Eligibility
Sex
ALL
Min age
18 Years
Max age
49 Years
Healthy volunteers
Accepted
Inclusion Criteria:
The main inclusion criteria include but are not limited to the following:
* 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
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
* 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.
Primary outcome measure(s)
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 — Predose (Day 1), Day 15 and Day 29 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.
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 — Predose (Day 1), Day 15 and Day 29 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.
Trial sites (4)
Facility
City
Region
Status
California Clinical Trials Medical Group (CCTMG) managed by Parexel
Glendale
California
Parexel ( Site 0001)
Glendale
California
Parexel ( Site 0002)
Baltimore
Maryland
Parexel International - EPCU Baltimore
Baltimore
Maryland
More Cidara Therapeutics Inc., a subsidiary of Merck & Co., Inc. (Rahway, New Jersey USA) trials in the USA
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
We use cookies to analyse site traffic and improve your experience. With your consent, we may also use cookies for advertising. You can change your choice at any time on our Cookie Policy page. See also our Privacy Policy.