Trial Outcomes & Findings for Study of the Safety and Immunogenicity of Reduced Doses of the US Yellow Fever Vaccine (NCT NCT05374317)
NCT ID: NCT05374317
Last Updated: 2026-04-07
Results Overview
Rate of Adverse Events of fractional doses vs standard dose of YF-VAX.
Recruitment status
COMPLETED
Study phase
PHASE4
Target enrollment
88 participants
Primary outcome timeframe
Up to 28 days post vaccination
Results posted on
2026-04-07
Participant Flow
Participant milestones
| Measure |
Standard Dose (Group 1)
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Overall Study
STARTED
|
29
|
30
|
29
|
|
Overall Study
COMPLETED
|
23
|
25
|
24
|
|
Overall Study
NOT COMPLETED
|
6
|
5
|
5
|
Reasons for withdrawal
Withdrawal data not reported
Baseline Characteristics
Study of the Safety and Immunogenicity of Reduced Doses of the US Yellow Fever Vaccine
Baseline characteristics by cohort
| Measure |
Standard Dose (Group 1)
n=29 Participants
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=30 Participants
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=29 Participants
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Total
n=88 Participants
Total of all reporting groups
|
|---|---|---|---|---|
|
Age, Categorical
<=18 years
|
0 Participants
n=527 Participants
|
0 Participants
n=527 Participants
|
0 Participants
n=1054 Participants
|
0 Participants
n=157 Participants
|
|
Age, Categorical
Between 18 and 65 years
|
29 Participants
n=527 Participants
|
30 Participants
n=527 Participants
|
29 Participants
n=1054 Participants
|
88 Participants
n=157 Participants
|
|
Age, Categorical
>=65 years
|
0 Participants
n=527 Participants
|
0 Participants
n=527 Participants
|
0 Participants
n=1054 Participants
|
0 Participants
n=157 Participants
|
|
Age, Continuous
|
34.2 Years
STANDARD_DEVIATION 9.4 • n=527 Participants
|
28.1 Years
STANDARD_DEVIATION 7.1 • n=527 Participants
|
35.2 Years
STANDARD_DEVIATION 10.2 • n=1054 Participants
|
32.5 Years
STANDARD_DEVIATION 9.4 • n=157 Participants
|
|
Sex: Female, Male
Female
|
13 Participants
n=527 Participants
|
13 Participants
n=527 Participants
|
12 Participants
n=1054 Participants
|
38 Participants
n=157 Participants
|
|
Sex: Female, Male
Male
|
16 Participants
n=527 Participants
|
17 Participants
n=527 Participants
|
17 Participants
n=1054 Participants
|
50 Participants
n=157 Participants
|
|
Ethnicity (NIH/OMB)
Hispanic or Latino
|
5 Participants
n=527 Participants
|
2 Participants
n=527 Participants
|
2 Participants
n=1054 Participants
|
9 Participants
n=157 Participants
|
|
Ethnicity (NIH/OMB)
Not Hispanic or Latino
|
23 Participants
n=527 Participants
|
23 Participants
n=527 Participants
|
25 Participants
n=1054 Participants
|
71 Participants
n=157 Participants
|
|
Ethnicity (NIH/OMB)
Unknown or Not Reported
|
1 Participants
n=527 Participants
|
5 Participants
n=527 Participants
|
2 Participants
n=1054 Participants
|
8 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · White
|
18 Participants
n=527 Participants
|
20 Participants
n=527 Participants
|
19 Participants
n=1054 Participants
|
57 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · Black/African American
|
3 Participants
n=527 Participants
|
1 Participants
n=527 Participants
|
3 Participants
n=1054 Participants
|
7 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · Asian
|
1 Participants
n=527 Participants
|
2 Participants
n=527 Participants
|
2 Participants
n=1054 Participants
|
5 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · Native Hawaiian/Pacific Islander
|
1 Participants
n=527 Participants
|
0 Participants
n=527 Participants
|
1 Participants
n=1054 Participants
|
2 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · American Indian/Alaskan Native
|
0 Participants
n=527 Participants
|
0 Participants
n=527 Participants
|
0 Participants
n=1054 Participants
|
0 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · Hispanic or Latino
|
5 Participants
n=527 Participants
|
2 Participants
n=527 Participants
|
2 Participants
n=1054 Participants
|
9 Participants
n=157 Participants
|
|
Race/Ethnicity, Customized
Race · Others
|
1 Participants
n=527 Participants
|
5 Participants
n=527 Participants
|
2 Participants
n=1054 Participants
|
8 Participants
n=157 Participants
|
|
Region of Enrollment
United States
|
29 participants
n=527 Participants
|
30 participants
n=527 Participants
|
29 participants
n=1054 Participants
|
88 participants
n=157 Participants
|
PRIMARY outcome
Timeframe: Up to 28 days post vaccinationPopulation: All participants who received a single dose of vaccine.
Rate of Adverse Events of fractional doses vs standard dose of YF-VAX.
Outcome measures
| Measure |
Standard Dose (Group 1)
n=29 Participants
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=30 Participants
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=29 Participants
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Adverse Events
|
26 Participants
|
27 Participants
|
28 Participants
|
PRIMARY outcome
Timeframe: The primary data point is day 28 post-vaccination.Population: All participants who received a single dose of vaccine and complied with day 28 study visit.
For each group determine the PRNT50 neutralizing antibody response rate at the primary data point at post-vaccination day 28.
Outcome measures
| Measure |
Standard Dose (Group 1)
n=27 Participants
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=29 Participants
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=28 Participants
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Neutralizing Antibody Response
|
26 Participants
|
27 Participants
|
28 Participants
|
SECONDARY outcome
Timeframe: First 14 days following vaccination.Compare the rate of viremia by Reverse Transcription Polymerase Chain Reaction (RT-PCR) \[copies/mL\] of fractional doses vs standard dose.
Outcome measures
| Measure |
Standard Dose (Group 1)
n=26 Participants
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=27 Participants
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=28 Participants
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Viremia
|
0 Participants
|
0 Participants
|
0 Participants
|
Adverse Events
Standard Dose (Group 1)
Serious events: 1 serious events
Other events: 15 other events
Deaths: 0 deaths
Fractional Dose (Group 2)
Serious events: 0 serious events
Other events: 11 other events
Deaths: 0 deaths
Fractional Dose (Group 3)
Serious events: 0 serious events
Other events: 7 other events
Deaths: 0 deaths
Serious adverse events
| Measure |
Standard Dose (Group 1)
n=29 participants at risk
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=30 participants at risk
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=29 participants at risk
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Musculoskeletal and connective tissue disorders
Broken Jaw
|
3.4%
1/29 • Number of events 1 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/30 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
Other adverse events
| Measure |
Standard Dose (Group 1)
n=29 participants at risk
Yellow Fever vaccine standard dose, 0.5mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 2)
n=30 participants at risk
Yellow Fever vaccine 1/5th standard dose, 0.1mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
Fractional Dose (Group 3)
n=29 participants at risk
Yellow Fever vaccine 1/10th standard dose, 0.05mL.
Yellow Fever Vaccine: Administered subcutaneously once.
|
|---|---|---|---|
|
Musculoskeletal and connective tissue disorders
Body Aches
|
6.9%
2/29 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
3.3%
1/30 • Number of events 1 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Blood and lymphatic system disorders
Bruise: Blood Draw Site
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.7%
2/30 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
General disorders
Injection Site Pain
|
27.6%
8/29 • Number of events 8 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
13.3%
4/30 • Number of events 4 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.9%
2/29 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Nervous system disorders
Headache
|
17.2%
5/29 • Number of events 5 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
13.3%
4/30 • Number of events 4 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
10.3%
3/29 • Number of events 3 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Respiratory, thoracic and mediastinal disorders
Nasal Congestion
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/30 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.9%
2/29 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Skin and subcutaneous tissue disorders
Bruise (vaccination site)
|
10.3%
3/29 • Number of events 3 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
3.3%
1/30 • Number of events 1 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Skin and subcutaneous tissue disorders
Erythema at Injection Site
|
24.1%
7/29 • Number of events 7 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.7%
2/30 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Skin and subcutaneous tissue disorders
Induration (vaccination site)
|
10.3%
3/29 • Number of events 3 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/30 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Blood and lymphatic system disorders
White Blood Cell Decreased
|
3.4%
1/29 • Number of events 1 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.7%
2/30 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
|
Blood and lymphatic system disorders
Neutrophil Count Decreased
|
3.4%
1/29 • Number of events 1 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
6.7%
2/30 • Number of events 2 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
0.00%
0/29 • Adverse Events collected Up to one year following vaccination.
Solicited and non-Solicited adverse events collected.
|
Additional Information
Results disclosure agreements
- Principal investigator is a sponsor employee
- Publication restrictions are in place