CompletedNCT00800605Updated Nov 24, 2025Results posted

Immunogenicity Study of an Inactivated Influenza Vaccine (Split Virus, Vero Cell Derived) to Prevent Culture Confirmed Influenza Infection

A Phase 3 interventional study of Vero cell-derived, trivalent, seasonal influenza vaccine and Placebo: Phosphate-buffered saline in Influenza, sponsored by Alachua Government Services, Inc.. Completed at 36 sites in United States. Open to participants aged 18 Years to 49 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-11-24.

Sponsored by Alachua Government Services, Inc. · Phase 3, Interventional, and Prevention

Phase: Phase 3
Study type: Interventional
Enrollment: 7,250
Allocation: Randomized
Ages: 18 Years to 49 Years
Sex: All

Study summary

The purpose of this study is to demonstrate the efficacy of an investigational Vero cell-derived, trivalent, seasonal influenza vaccine to prevent infection with an influenza virus that is antigenically similar to one of the three strains in the vaccine. Subjects will be randomized in a double-blind fashion to receive a single intramuscular injection of either the investigational vaccine or placebo. Blood will be drawn from all subjects for a determination of hemagglutination inhibition antibody titers on Days 0 and 21, body temperature and injection site reactions will be monitored daily for 7 days. In addition, subjects must return to the clinic promptly to have swab samples of their nose and throat taken whenever they feel flu symptoms and all subjects will be monitored for adverse events until Day 180.

Conditions studied

Influenza

Browse trials for

Influenza, Human 2,214

In context

Influenza, Human

2,214 studies on the registry are indexed under Influenza, Human; 163 are open to participants now.

This study's enrollment of 7,250 is above the median of 238 across 1,853 interventional studies indexed under Influenza, Human.

Browse Influenza, Human studies →

Lead sponsor

Alachua Government Services, Inc. is the lead sponsor of 4 studies on the registry; none are open to participants now.

Counted across the registry records on this site, refreshed daily.

Who can participate

Ages eligible: 18 Years to 49 Years
Sexes eligible: All
Accepts healthy volunteers: Yes

Inclusion criteria

Subject has an understanding of the study
Subject agrees to study provisions
Subject gives written informed consent prior to study entry
Subject is accessible by telephone or electronic mail to receive reminders from the study site
If female and capable of bearing children, subject has a negative urine pregnancy test result within 24 hours of the vaccination on Study Day 0 and agrees to employ adequate birth control measures through the first 60 post-vaccination days.

Exclusion criteria

Exclusion Criteria:

Subject has any of the risk factors for complications from influenza infection as defined by the Centers for Disease Control and Prevention (CDC, 2008a):
- Pregnancy
- Chronic disorders of the pulmonary or cardiovascular system including asthma (hypertension is not considered a high risk condition)
- Chronic renal disorders
- Chronic hepatic disorders
- Chronic hematological disorders
- Chronic metabolic disorder (including diabetes mellitus and thyroid disorders)
- Immunosuppression (including immunosuppression caused by medications, congenital etiologies or HIV)
- Any condition that can compromise respiratory function or the handling of respiratory secretions or that can increase risk for aspiration (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders or other neuromuscular disorders)
- Residence in nursing home or other chronic care facility that houses persons of any age who have chronic medical conditions
- Household contact with children aged 0 to 59 months or of someone who is included in the risk categories listed above
- Employment as a health care worker
Subject is unable to lead an independent life as a result of either physical or mental handicap
Subject has a history of severe allergic reactions or anaphylaxis (e.g., urticaria or asthma that is clinically severe)
Subject has an oral temperature of >= 99.5° F (37.5°C) on the day of vaccination in this study. [NOTE: A subject meeting this exclusion criterion may be rescheduled for vaccination and study entry at a later date provided that certain requirements [in the study protocol] are met)
Subject has a rash or dermatologic condition or tattoos which may interfere with injection site reaction rating
Subject has received a blood transfusion, blood products or immunoglobulins within 90 days of study entry
Subject has received a live vaccine within 4 weeks or inactivated or subunit vaccine within 2 weeks of study entry
Subject has previously been vaccinated against influenza for the 2008/2009 northern hemisphere influenza season
Subject has a functional or surgical asplenia
Subject has a known or suspected problem with alcohol or drug abuse;
Subject was administered an investigational drug within six weeks prior to study entry or are concurrently participating in a clinical study that includes the administration of an investigational product
Subject is a member of the team conducting this study or are in a dependent relationship with the study investigator. Dependent relationships include close relatives (i.e., children, spouse/partner, siblings, parents) as well as employees of the investigator

Study design

Phase: Phase 3
Primary purpose: Prevention
Allocation: Randomized
Intervention model: Parallel assignment
Masking: Double (Participant, Investigator)
Enrollment: 7,250 participants (actual)

Study arms

Experimental
1
Vero cell-derived, trivalent, seasonal influenza vaccine
Biological: Vero cell-derived, trivalent, seasonal influenza vaccine
Placebo comparator
2
Phosphate-buffered saline
Biological: Placebo: Phosphate-buffered saline

Interventions

BiologicalVero cell-derived, trivalent, seasonal influenza vaccine
Single intramuscular injection
BiologicalPlacebo: Phosphate-buffered saline
Single intramuscular injection

What researchers measure

Primary outcomes

Efficacy of an Investigational Vero Cell-derived Influenza Vaccine to Prevent Infection With an Influenza Virus That is Antigenically Similar to One of the Three Strains in the Vaccine
The number of subjects developing influenza infection, as confirmed by viral culture and typing of naso-pharyngeal specimens, with a virus that is antigenically similar to one of the strains contained in the vaccine 21 days to 180 days after the date of vaccination.
Time frame: 180 days

Secondary outcomes

Number of Subjects Who Developed Influenza Infection 21 Days to 180 Days Post-vaccination With Infecting Strain Matching the Strains Contained in the Vaccine
Number of subjects with influenza infection confirmed by viral culture and typing and/or RT-PCR analysis of naso-pharyngeal specimens that are antigenically similar to the strains contained in the vaccine
Time frame: 180 days
Number of Subjects Who Developed Influenza Infection Between 21 and 180 Days Post-vaccination, Regardless of Whether the Infecting Strain Matched the Vaccine Strains Antigenically
Number of subjects with influenza infection as confirmed by viral culture and typing of naso-pharyngeal specimens regardless of whether the isolate is antigenically matched to the strains contained in the vaccine
Time frame: 180 days
HIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21
Time frame: 21 days
Percentage of Subjects With Seroprotective Antibody Titer [Reciprocal HIA Titer ≥ 40] for Each of the Three Antigens Contained in the Vaccine at Day 21
Time frame: 21 days
Fold Increase of HIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21 as Compared to Baseline
Time frame: 21 days
Percentage of Subjects Demonstrating Seroconversion to Each of the Three Antigens Contained in the Vaccine at Day 21
Seroconversion is defined as a ≥ 4-fold increase in HIA titer from baseline or a HIA titer ≥ 40 when there is no detectable HIA titer (HIA titer \<10) at baseline.
Time frame: 21 days
Frequency and Severity of Occurrence of Any Injection Site Reactions Related to Vaccination
Number of Subjects With Non-Serious Local Reactions During the Entire Follow-Up Period
Time frame: 180 days
Frequency and Severity of Occurrence of Any Injection Site Reactions and Systemic AEs Observed During the Entire 180-day Follow-up Period
Time frame: 180 days
Frequency and Severity of Occurrence of Any Systemic Reactions Related to Vaccination
Number of Subjects With Non-Serious Systemic Reactions During the Entire Follow-Up Period
Time frame: 180 days

Results

Posted Nov 24, 2025

Participant flow

Participant flow — Overall Study
Milestone	VCIV	Placebo
Started	3626	3624
Completed	3421	3415
Not completed	205	209

Outcome measures

PrimaryEfficacy of an Investigational Vero Cell-derived Influenza Vaccine to Prevent Infection With an Influenza Virus That is Antigenically Similar to One of the Three Strains in the Vaccine

The number of subjects developing influenza infection, as confirmed by viral culture and typing of naso-pharyngeal specimens, with a virus that is antigenically similar to one of the strains contained in the vaccine 21 days to 180 days after the date of vaccination.

Time frame:: 180 days
Reported as:: Count of participants · Participants

Efficacy of an Investigational Vero Cell-derived Influenza Vaccine to Prevent Infection With an Influenza Virus That is Antigenically Similar to One of the Three Strains in the Vaccine
Participants	VCIV	Placebo
Influenza Infections A/H1N1 Strain	11	52
Influenza Infections A/H3N2 Strain	2	4
Influenza Infections B Strains	0	4
No Influenza Infections	3606	3557

SecondaryNumber of Subjects Who Developed Influenza Infection 21 Days to 180 Days Post-vaccination With Infecting Strain Matching the Strains Contained in the Vaccine

Number of subjects with influenza infection confirmed by viral culture and typing and/or RT-PCR analysis of naso-pharyngeal specimens that are antigenically similar to the strains contained in the vaccine

Time frame:: 180 days
Reported as:: Count of participants · Participants

Number of Subjects Who Developed Influenza Infection 21 Days to 180 Days Post-vaccination With Infecting Strain Matching the Strains Contained in the Vaccine
Participants	VCIV	Placebo
Influenza Infection A/H1N1	14	56
Influenza Infection A/H3N2	2	4
Influenza Infection B	8	20
No Influenza Infection	3595	3537

SecondaryNumber of Subjects Who Developed Influenza Infection Between 21 and 180 Days Post-vaccination, Regardless of Whether the Infecting Strain Matched the Vaccine Strains Antigenically

Number of subjects with influenza infection as confirmed by viral culture and typing of naso-pharyngeal specimens regardless of whether the isolate is antigenically matched to the strains contained in the vaccine

Time frame:: 180 days
Reported as:: Count of participants · Participants

Number of Subjects Who Developed Influenza Infection Between 21 and 180 Days Post-vaccination, Regardless of Whether the Infecting Strain Matched the Vaccine Strains Antigenically
Participants	VCIV	Placebo
Influenza Infection A/H1N1	11	52
Influenza Infection A/H3N2	2	4
Influenza Infection B	8	18
No Influenza Infection	3598	3543

SecondaryHIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21

Time frame:: 21 days
Reported as:: Geometric mean · Titers

HIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21
Titers	VCIV	Placebo
A/H1N1	194.1 (184.4 to 204.3)	17.7 (17 to 18.4)
A/H3N2	299.7 (285.2 to 314.9)	22.4 (21.3 to 23.5)
B	301.7 (290.5 to 313.4)	39.3 (37.6 to 41.2)

SecondaryPercentage of Subjects With Seroprotective Antibody Titer [Reciprocal HIA Titer ≥ 40] for Each of the Three Antigens Contained in the Vaccine at Day 21

Time frame:: 21 days
Reported as:: Number · percentage of participants

Percentage of Subjects With Seroprotective Antibody Titer [Reciprocal HIA Titer ≥ 40] for Each of the Three Antigens Contained in the Vaccine at Day 21
percentage of participants	VCIV	Placebo
A/H1N1	88 (86.8 to 89)	29.8 (28.3 to 31.4)
A/H3N2	93.3 (92.4 to 94.1)	38.8 (37.2 to 40.5)
B	97.1 (96.5 to 97.7)	56.2 (54.5 to 57.8)

SecondaryFold Increase of HIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21 as Compared to Baseline

Time frame:: 21 days
Reported as:: Geometric mean · Fold change

Fold Increase of HIA Titer for Each of the Three Antigens Contained in the Vaccine at Day 21 as Compared to Baseline
Fold change	VCIV	Placebo
A/H1N1	11.11 (10.52 to 11.74)	1.06 (1.04 to 1.08)
A/H3N2	13.51 (12.85 to 14.2)	1.01 (1 to 1.02)
B	7.58 (7.22 to 7.97)	1.03 (1.02 to 1.05)

SecondaryPercentage of Subjects Demonstrating Seroconversion to Each of the Three Antigens Contained in the Vaccine at Day 21

Seroconversion is defined as a ≥ 4-fold increase in HIA titer from baseline or a HIA titer ≥ 40 when there is no detectable HIA titer (HIA titer \<10) at baseline.

Time frame:: 21 days
Reported as:: Number · percentage of participants

Percentage of Subjects Demonstrating Seroconversion to Each of the Three Antigens Contained in the Vaccine at Day 21
percentage of participants	VCIV	Placebo
A/H1N1	70.4 (68.9 to 71.9)	1.2 (0.9 to 1.6)
A/H3N2	79.1 (77.7 to 80.4)	0.9 (0.6 to 1.3)
B	65.7 (64.1 to 67.3)	1.3 (1 to 1.7)

SecondaryFrequency and Severity of Occurrence of Any Injection Site Reactions Related to Vaccination

Number of Subjects With Non-Serious Local Reactions During the Entire Follow-Up Period

Time frame:: 180 days
Reported as:: Number · participants

Frequency and Severity of Occurrence of Any Injection Site Reactions Related to Vaccination
participants	VCIV	Placebo
No Reaction	1994	3309
Mild	1354	262
Moderate	107	6
Severe	9	1
Unknown	159	42
Total with Reaction	1629	311

SecondaryFrequency and Severity of Occurrence of Any Injection Site Reactions and Systemic AEs Observed During the Entire 180-day Follow-up Period

Time frame:: 180 days
Reported as:: Number · participants

Frequency and Severity of Occurrence of Any Injection Site Reactions and Systemic AEs Observed During the Entire 180-day Follow-up Period
participants	VCIV	Placebo
Serious AEs	29	27
Non-Serious Moderate or Severe Systemic AEs	924	858
Any Non-Serious Systemic AEs	2176	1945
Non-Serious Moderate or Severe Local AEs	121	7
Any Non-Serious Local AEs	1629	311

SecondaryFrequency and Severity of Occurrence of Any Systemic Reactions Related to Vaccination

Number of Subjects With Non-Serious Systemic Reactions During the Entire Follow-Up Period

Time frame:: 180 days
Reported as:: Number · participants

Frequency and Severity of Occurrence of Any Systemic Reactions Related to Vaccination
participants	VCIV	Placebo
No Reaction	2312	2748
Mild	957	648
Moderate	250	173
Severe	53	17
Unknown	51	34
Total with Reaction	1311	872

Adverse events

Non-serious events are listed at a 0.1% frequency threshold.

Adverse event summary by group
Group	Deaths	Serious	Other
VCIV	2/3,623 (0.1%)	29/3,623 (0.8%)	2,176/3,623 (60.1%)
Placebo	0/3,620 (0%)	27/3,620 (0.7%)	1,945/3,620 (53.7%)

Most frequent serious events

Showing 10 of 53

Most frequent serious events
Event	VCIV	Placebo
Abortion spontaneousPregnancy, puerperium and perinatal conditions	0/3623	4/3620
Selective abortionSurgical and medical procedures	0/3623	3/3620
InjuryInjury, poisoning and procedural complications	3/3623	0/3620
AppendicitisInfections and infestations	2/3623	2/3620
Breast cancerNeoplasms benign, malignant and unspecified (incl cysts and polyps)	1/3623	2/3620
PneumoniaInfections and infestations	1/3623	2/3620
GastroenteritisInfections and infestations	2/3623	0/3620
Lung injuryInjury, poisoning and procedural complications	0/3623	1/3620
Back painMusculoskeletal and connective tissue disorders	0/3623	1/3620
PancreatitisGastrointestinal disorders	0/3623	1/3620

Most frequent other events

Showing 10 of 105

Most frequent other events
Event	VCIV	Placebo
Injection Site PainGeneral disorders	1571/3623	274/3620
HeadacheNervous system disorders	1408/3623	1292/3620
FatigueGeneral disorders	1189/3623	1004/3620
MyalgiaMusculoskeletal and connective tissue disorders	1042/3623	648/3620
MalaiseGeneral disorders	837/3623	537/3620
Oropharyngeal PainRespiratory, thoracic and mediastinal disorders	529/3623	506/3620
CoughRespiratory, thoracic and mediastinal disorders	470/3623	476/3620
ChillsGeneral disorders	359/3623	226/3620
ArthralgiaMusculoskeletal and connective tissue disorders	335/3623	217/3620
PyrexiaGeneral disorders	270/3623	273/3620

Baseline characteristics

Safety Analysis Population

Age, Continuous
Age, Continuous(years)	VCIV	Placebo	Total
Mean	32.2 ± 9.7	32.1 ± 9.7	32.1 ± 9.7

Sex: Female, Male
Sex: Female, Male(Participants)	VCIV	Placebo	Total
Female	1800	1755	3555
Male	1823	1865	3688

Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)	VCIV	Placebo	Total
Hispanic or Latino	616	638	1254
Not Hispanic or Latino	3007	2982	5989
Unknown or Not Reported	0	0	0

Race (NIH/OMB)
Race (NIH/OMB)(Participants)	VCIV	Placebo	Total
American Indian or Alaska Native	14	25	39
Asian	60	37	97
Native Hawaiian or Other Pacific Islander	12	10	22
Black or African American	771	741	1512
White	2746	2784	5530
More than one race	20	21	41
Unknown or Not Reported	0	2	2

Weight
Weight(kg)	VCIV	Placebo	Total
Mean	83.6 ± 22	83.3 ± 21.1	83.5 ± 21.6

Height
Height(cm)	VCIV	Placebo	Total
Mean	171.6 ± 10	171.9 ± 10.2	171.7 ± 10.1

Study locations

36 sites

Quality of Life Medical & Research Center, LLC
Tucson, Arizona 85712, United States
Benchmark Research
Sacramento, California 95816, United States
California Research Foundation
San Diego, California 92103, United States
Benchmark Research San Francisco
San Francisco, California 94102, United States
Radiant Research, Inc
Denver, Colorado 80239, United States
Clinical Research of South Florida
Coral Gables, Florida 33134, United States
Jacksonville Center for Clinical Research
Jacksonville, Florida 32216, United States
Pharmax Research Clinic
Miami, Florida 33126, United States
University Clinical Research, Inc
Pembroke Pines, Florida 33024, United States
Miami Research Associates
South Miami, Florida 33143, United States
Clinical Research Atlanta
Stockbridge, Georgia 30281, United States
Radiant Research, Inc - Chicago
Chicago, Illinois 60654, United States
Johnson County Clin-Trials
Lenexa, Kansas 66219, United States
Vince and Associates Clinical Research
Overland Park, Kansas 66212, United States
Central Kentucky Research Associates, Inc.
Lexington, Kentucky 40509, United States
Benchmark Research
Metairie, Louisiana 70006, United States
Center for Pharmaceutical Research
Kansas City, Missouri 64114, United States
Radiant Research, Inc.
St Louis, Missouri 63141, United States
Sundance Clinical Research
St Louis, Missouri 63141, United States
Meridian Clinical Research, LLC
Omaha, Nebraska 68134, United States
Regional Clinical Research, Inc.
Endwell, New York 13760, United States
Rochester Clinical Research, Inc.
Rochester, New York 14609, United States
Triangle Medical Research Associates
Raleigh, North Carolina 27609, United States
Wake Research Associates, LLC
Raleigh, North Carolina 27612, United States
Radiant Research - Cincinnati
Cincinnati, Ohio 45249, United States
Omega Medical Research
Warwick, Rhode Island 02886, United States
Spartanburg Medical Research
Spartanburg, South Carolina 29303, United States
Health Concepts
Rapid City, South Dakota 57702, United States
Clinical Research Associates, Inc. - Nashville
Nashville, Tennessee 37203, United States
Benchmark Research Austin
Austin, Texas 78705, United States
Benchmark Research Ft. Worth
Fort Worth, Texas 76135, United States
Benchmark Research San Angeolo
San Angelo, Texas 76904, United States
Jean Brown Research / Westside Medical
Salt Lake City, Utah 84124, United States
Advanced Clinical Research
West Jordan, Utah 84088, United States
PI-COOR Clinical Research
Burke, Virginia 22015, United States
Clinical Research Associates of Tidewater
Norfolk, Virginia 23507, United States

Updates

Tracking since Sep 25, 2026

No changes since tracking began. The registry record was last updated on Nov 24, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗

Registry details

Key details

Study ID: NCT00800605
Lead sponsor: Alachua Government Services, Inc.
Responsible party: Sponsor
First posted: Dec 2, 2008
Start date: Dec 2008
Primary completion: May 2009
Completion: Jun 2009
Results posted: Nov 24, 2025
Last update: Nov 24, 2025

Study contacts

Baxter Bio Science Investigator, MD

study director · Baxter Healthcare Corporation

Oversight

Data monitoring committee: Yes

View the source record on ClinicalTrials.gov ↗

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