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Mood and Influenza Vaccine Response: A Feasibility Trial

A Feasibility Trial of a Brief Positive Affect Intervention to Improve the Effectiveness of Influenza Vaccine Response in Older Adults.

Status
Completed
Phases
NA
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT03144518
Enrollment
106
Registered
2017-05-08
Start date
2017-09-01
Completion date
2018-05-31
Last updated
2019-07-15

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Vaccination; Infection

Keywords

Positive Affect, Positive Mood, Influenza Vaccination, Vaccination, Randomised Controlled Trial

Brief summary

This study is a 2-arm, parallel, randomised controlled feasibility trial of a brief video intervention designed to induce positive affect (mood) in older adults in primary care settings prior to the receipt of influenza vaccination. Participants will be randomised into two conditions: experimental and active control. In the experimental condition, participants will view the approximately 15 minute long intervention video immediately prior to vaccination. In the active control condition, participants will view a matched video that is designed to be mood neutral. Pre-and-post positive affect levels will be assessed by self-report questionnaires. Immune response to the intervention and vaccination responses will be assessed in saliva and serum samples respectively. The objectives of the study are to assess the impact of the intervention on mood, immune function, and antibody response to influenza vaccination in older adults. This feasibility trial will also allow data collection on exploring recruitment, attrition, intervention engagement, and practicality of collecting clinical data available through electronic records to inform the design of a future definitive trial.

Detailed description

The Centers for Disease Control (CDC) describe vaccinations as among the 10 most significant health achievements ever documented; and for many conditions they have been an unmitigated success (e.g., smallpox). There are, however, several populations in whom vaccine effectiveness is far from optimal. These populations are typically contending with underlying immune impairment by virtue of their advancing age and/or the presence of co-existing diseases (e.g., cancer). As a consequence, vaccines are most likely to fail those whom they most seek to benefit: individuals at the greatest risk of ill health. This has prompted research into treatments that enhance immune function prior to vaccination, so called vaccine adjuvants. The aim of such treatments is to optimise the response the immune system makes to the vaccine antigens and, in so doing, increase the likelihood that the vaccine confers protection. One area in which there has been interest is in the potential for developing psycho-behavioural vaccine adjuvants. There is considerable evidence that psychological and behavioural factors can modulate immunity; with diet, physical activity, stress, affect, sleep and social support all associated with immune response. The investigators recently conducted a longitudinal observational cohort study of multiple psychological (positive affect, negative affect, stress) and behavioural (physical activity, sleep, diet) influences on short and long-term antibody responses to influenza vaccination in older adults. This identified positive affect as the most influential psycho-behavioural factor on influenza-specific antibody responses, independently predicting both short and long-term antibody responses in the weakest immunogenic strain above and beyond known demographic and clinical determinants. Intriguingly, the investigators also observed preliminary evidence that positive affect on the day of vaccination was more predictive of antibody responses following vaccination than mood measured over the longer period surrounding vaccination. As influenza-specific antibodies are a well-established correlate of protection from serologically and clinically diagnosed influenza incidence, these data suggest that increasing positive affect immediately prior to vaccination could be used as a non-pharmacological vaccine adjuvant. Through a series of systematic steps, including focus groups and interviews with older adults and health care professionals, the investigators have recently developed a brief, positive affect intervention - designed to improve short-term mood in older adults and be deliverable within primary care. It is hoped this could act as a psycho-behavioural adjuvant to enhance poor responses to influenza vaccination in older adults. Before performing a definitive trial of the intervention's effectiveness, a feasibility trial is needed for number of reasons: 1. To assess whether our intervention can enhance positive affect (mood) 2. To collect information regarding likely recruitment, effect sizes, and attrition rates for informing the necessary size of a larger definitive trial 3. To examine the practicality and acceptability of delivering the intervention in routine primary care settings 4. To explore the feasibility of obtaining outcome data on healthcare usage for a large scale trial (hospitalisation, GP visits for flu-like symptoms from medical records) In line with the above, the investigators will be conducting a 2-arm, parallel, randomised controlled feasibility trial of a brief video intervention designed to induce positive affect (mood) in older adults in primary care settings prior to the receipt of influenza vaccination. Participants will be randomised into two conditions: experimental and active control. In the experimental condition, participants will view the approximately 15 minute long intervention video immediately prior to vaccination. In the active control condition, participants will view a matched video that is designed to be mood neutral. Pre-and-post positive affect levels will be assessed by self-report questionnaires. Immune response to the intervention and vaccination responses will be assessed in saliva (pre/post intervention) and serum samples (pre/4 weeks post-vaccination/16weeks post-vaccination) respectively.

Interventions

OTHERPositive Affect Intervention

See Previous Description

OTHERNeutral Control Intervention

See Previous Description

BIOLOGICALNorthern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care)

Northern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care)

Sponsors

Northumbria University
CollaboratorOTHER
University of Nottingham
Lead SponsorOTHER

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
QUADRUPLE (Subject, Caregiver, Investigator, Outcomes Assessor)

Eligibility

Sex/Gender
ALL
Age
65 Years to 85 Years
Healthy volunteers
Yes

Inclusion criteria

* Males and Females aged 65-85 years (inclusive) * Received influenza vaccination for the 2016/17 season * Eligible to receive 2017/18 influenza vaccination as part of usual care * Ability to give informed consent

Exclusion criteria

* Males and Females aged less than 65 or over 85 years (exclusive) * Did not receive influenza vaccination for the 2016/17 season * Ineligible to receive 2017/18 influenza vaccination as part of usual care * Unable to provide informed consent Deemed by health care provider to be: * Too physically frail to participate * Diagnosed with dementia or other cognitive condition which would make participation difficult * Insufficient command of English language * Influenza vaccination contraindicated * Sufficiently impaired of hearing or vision that exposure to the intervention or control video content as intended would be compromised * Those for whom the collection of blood samples is contraindicated.

Design outcomes

Primary

MeasureTime frameDescription
Mood Outcome Scores [Multiple]Baseline, Immediately Post Intervention (i.e, 15 minutes post-baseline).Affective Slider (Betella & Verschure, 2016), consists of two single item visual analogue scales. Scores for each are presented as a value from 0 to 100 with higher scores indicating greater pleasure (VAS-Valence) and arousal (VAS-Arousal). Positive and Negative Affect Schedule (Watson et al., 1988). Positive and negative affect subscales were created by summing the scores of positive and negative adjectives respectively. For each sub scale, minimum score = 10, maximum score = 50 with higher scores indicating greater positive and negative affect respectively. Pictorial scale of positive affect (unvalidated, internally developed). Participants completed a single-item photo-based measure of positive affect tailored for older adults. Participants were presented with six groups of images depicting varying degrees of positive affect, and indicate which best reflected how they felt at that moment. Minumum score 1, maximum score 6, higher scores indicate greater positive affect.

Secondary

MeasureTime frameDescription
RecruitmentBaselineRecruitment rates to inform a future definitive trial
Attrition4 weeks (post-vaccination), 16 Weeks (post-vaccination)Attrition - to inform a future definitive trial
Secretory IgA ResponseBaseline, Immediately Post Intervention (i.e, 15 minutes post-baseline).Secretory IgA levels measured in saliva samples via ELISA. This is a non-specific measure of immunological response
Vaccine Specific IgG Response4 weeks (post-vaccination), 16 Weeks (post-vaccination)IgG levels against the 4 vaccine strains measured via ELISA. Values represent equivalent ug/ml based on diluted sample absorbance value interpolation against a standard IgG curve, multiplied by the serum dilution score (i.e., 4000).
Health Care UtilizationBaseline to 6 months post-vaccinationVia medical records, we assessed health care usage potentially attributable to flu-like symptoms (e.g., GP visits, hospitalisation, antibiotic prescription) during the 6 months post-vaccination

Countries

United Kingdom

Participant flow

Pre-assignment details

Note: 3 Participants were not randomised to condition, as they did not attend primary session.

Participants by arm

ArmCount
Experimental
Participants in the experimental condition will view a video designed to induce positive affect. This includes 3 short comedy clips (fork handles sketch, the two Ronnie's; A room with a view - faulty towers; Tim Vine Live stand-up extract), uplifting music (Jailhouse Rock - Elvis Presley; Happy Together - The Turtles), jokes and positive imagery. The content of the intervention has been informed by patient and public involvement, focus groups with older adults, and pilot testing. Positive Affect Intervention: See Previous Description Northern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care): Northern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care)
52
Active Control
Participants in the control condition will view a video of matched length to the experimental condition video, but not designed to induce mood change. This includes short documentary clips (a pride in pencils; model railways, lecture extract on hydration), neutral music and images. Neutral Control Intervention: See Previous Description Northern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care): Northern Hemisphere Influenza Vaccine 2017/18 (Delivered as part of Standard Care)
51
Total103

Baseline characteristics

CharacteristicTotalExperimentalActive Control
Age, Continuous72.95 years
STANDARD_DEVIATION 4.87
72.6 years
STANDARD_DEVIATION 4.6
73.3 years
STANDARD_DEVIATION 5.1
Current Smoker8 Participants4 Participants4 Participants
Highest Ever Total Household Income
≥ £100,000
0 Participants0 Participants0 Participants
Highest Ever Total Household Income
≤ £14,999
33 Participants17 Participants16 Participants
Highest Ever Total Household Income
£15,000-£24,999
33 Participants16 Participants17 Participants
Highest Ever Total Household Income
£25,000-£34,999
12 Participants8 Participants4 Participants
Highest Ever Total Household Income
£35,000-£49,000
12 Participants7 Participants5 Participants
Highest Ever Total Household Income
£50,000-£74,999
3 Participants1 Participants2 Participants
Highest Ever Total Household Income
£75,000-£99,000
0 Participants0 Participants0 Participants
Highest Ever Total Household Income
Did Not Respond
10 Participants3 Participants7 Participants
Highest Level of Education
Did not respond
7 Participants5 Participants2 Participants
Highest Level of Education
Other
16 Participants8 Participants8 Participants
Highest Level of Education
Postgraduate
1 Participants0 Participants1 Participants
Highest Level of Education
School
77 Participants37 Participants40 Participants
Highest Level of Education
Undergraduate
2 Participants2 Participants0 Participants
Independent Living
No
7 Participants5 Participants2 Participants
Independent Living
Yes
96 Participants47 Participants49 Participants
Marital Status
Cohabiting
6 Participants3 Participants3 Participants
Marital Status
Did not Respond
6 Participants2 Participants4 Participants
Marital Status
Married
63 Participants34 Participants29 Participants
Marital Status
Separated/divorced
13 Participants9 Participants4 Participants
Marital Status
Single, never married
3 Participants0 Participants3 Participants
Marital Status
Widowed
12 Participants4 Participants8 Participants
Pre-Vaccination IgG
A/Hong-Kong
239.50 ug/ml
STANDARD_DEVIATION 139.42
238.0 ug/ml
STANDARD_DEVIATION 119.9
241.0 ug/ml
STANDARD_DEVIATION 158.1
Pre-Vaccination IgG
A/Michigan
172.05 ug/ml
STANDARD_DEVIATION 108.47
187.2 ug/ml
STANDARD_DEVIATION 112.4
156.6 ug/ml
STANDARD_DEVIATION 103.1
Pre-Vaccination IgG
B/Brisbane
112.90 ug/ml
STANDARD_DEVIATION 67.35
107.0 ug/ml
STANDARD_DEVIATION 54.1
118.9 ug/ml
STANDARD_DEVIATION 78.7
Pre-Vaccination IgG
B/Phuket
163.61 ug/ml
STANDARD_DEVIATION 117.93
144.4 ug/ml
STANDARD_DEVIATION 85.1
183.2 ug/ml
STANDARD_DEVIATION 146.2
Race/Ethnicity, Customized
Asian
1 Participants0 Participants1 Participants
Race/Ethnicity, Customized
Black
2 Participants1 Participants1 Participants
Race/Ethnicity, Customized
Did not Respond
1 Participants0 Participants1 Participants
Race/Ethnicity, Customized
White
99 Participants51 Participants48 Participants
Sex: Female, Male
Female
52 Participants22 Participants30 Participants
Sex: Female, Male
Male
51 Participants30 Participants21 Participants
Total Health Status555.41 units on a scale
STANDARD_DEVIATION 171.62
555.7 units on a scale
STANDARD_DEVIATION 175.1
555.1 units on a scale
STANDARD_DEVIATION 169.9
Trait Emotional Reactivity40.59 units on a scale
STANDARD_DEVIATION 16.52
39.9 units on a scale
STANDARD_DEVIATION 17.2
41.3 units on a scale
STANDARD_DEVIATION 16
Trait Negative Affect15.35 units on a scale
STANDARD_DEVIATION 6.52
15.2 units on a scale
STANDARD_DEVIATION 6.7
15.5 units on a scale
STANDARD_DEVIATION 6.4
Trait Optimism15.68 units on a scale
STANDARD_DEVIATION 4.61
16.0 units on a scale
STANDARD_DEVIATION 4.8
15.3 units on a scale
STANDARD_DEVIATION 4.5
Trait Positive Affect33.65 units on a scale
STANDARD_DEVIATION 8.33
33.5 units on a scale
STANDARD_DEVIATION 8.6
33.8 units on a scale
STANDARD_DEVIATION 8.1

Adverse events

Event typeEG000
affected / at risk
EG001
affected / at risk
deaths
Total, all-cause mortality
0 / 520 / 51
other
Total, other adverse events
0 / 520 / 51
serious
Total, serious adverse events
0 / 520 / 51

Outcome results

Primary

Mood Outcome Scores [Multiple]

Affective Slider (Betella & Verschure, 2016), consists of two single item visual analogue scales. Scores for each are presented as a value from 0 to 100 with higher scores indicating greater pleasure (VAS-Valence) and arousal (VAS-Arousal). Positive and Negative Affect Schedule (Watson et al., 1988). Positive and negative affect subscales were created by summing the scores of positive and negative adjectives respectively. For each sub scale, minimum score = 10, maximum score = 50 with higher scores indicating greater positive and negative affect respectively. Pictorial scale of positive affect (unvalidated, internally developed). Participants completed a single-item photo-based measure of positive affect tailored for older adults. Participants were presented with six groups of images depicting varying degrees of positive affect, and indicate which best reflected how they felt at that moment. Minumum score 1, maximum score 6, higher scores indicate greater positive affect.

Time frame: Baseline, Immediately Post Intervention (i.e, 15 minutes post-baseline).

Population: Missing Data for some outcome measures - i.e., incomplete scale

ArmMeasureGroupValue (MEAN)Dispersion
ExperimentalMood Outcome Scores [Multiple]Post-Intervention VAS-Valence87.4 score on a scaleStandard Deviation 15.7
ExperimentalMood Outcome Scores [Multiple]Post-Intervention VAS-Arousal83.7 score on a scaleStandard Deviation 16.8
ExperimentalMood Outcome Scores [Multiple]Post-Intervention Pictorial Scale4.7 score on a scaleStandard Deviation 1.1
ExperimentalMood Outcome Scores [Multiple]Post-Intervention PANAS Positive Affect35.0 score on a scaleStandard Deviation 8.4
ExperimentalMood Outcome Scores [Multiple]Post-Intervention PANAS Negative Affect11.1 score on a scaleStandard Deviation 3
ExperimentalMood Outcome Scores [Multiple]Pre-Intervention VAS-Valence79.5 score on a scaleStandard Deviation 19.2
ExperimentalMood Outcome Scores [Multiple]Pre-Intervention VAS-Arousal79.9 score on a scaleStandard Deviation 19
ExperimentalMood Outcome Scores [Multiple]Pre-Intervention Pictorial3.7 score on a scaleStandard Deviation 1.5
ExperimentalMood Outcome Scores [Multiple]Pre-Intervention PANAS Postive Affect34.3 score on a scaleStandard Deviation 7.2
ExperimentalMood Outcome Scores [Multiple]Pre-Intervention PANAS Negative Affect12.3 score on a scaleStandard Deviation 4
Active ControlMood Outcome Scores [Multiple]Pre-Intervention Pictorial4.0 score on a scaleStandard Deviation 1.5
Active ControlMood Outcome Scores [Multiple]Post-Intervention VAS-Valence79.8 score on a scaleStandard Deviation 20.8
Active ControlMood Outcome Scores [Multiple]Pre-Intervention VAS-Valence80.5 score on a scaleStandard Deviation 18.1
Active ControlMood Outcome Scores [Multiple]Post-Intervention VAS-Arousal79.8 score on a scaleStandard Deviation 20.3
Active ControlMood Outcome Scores [Multiple]Pre-Intervention PANAS Negative Affect12.3 score on a scaleStandard Deviation 4
Active ControlMood Outcome Scores [Multiple]Post-Intervention Pictorial Scale4.0 score on a scaleStandard Deviation 1.5
Active ControlMood Outcome Scores [Multiple]Pre-Intervention VAS-Arousal80.9 score on a scaleStandard Deviation 20.1
Active ControlMood Outcome Scores [Multiple]Post-Intervention PANAS Positive Affect35.0 score on a scaleStandard Deviation 7.6
Active ControlMood Outcome Scores [Multiple]Pre-Intervention PANAS Postive Affect34.6 score on a scaleStandard Deviation 35
Active ControlMood Outcome Scores [Multiple]Post-Intervention PANAS Negative Affect11.4 score on a scaleStandard Deviation 2.3
Comparison: VAS-Valence Scoresp-value: 0.00590% CI: [0.014, 0.173]ANCOVA
Comparison: VAS-Arousal Scoresp-value: 0.04790% CI: [0, 0.12]ANCOVA
Comparison: Pictorial Scalep-value: 0.00290% CI: [0.022, 0.196]ANCOVA
Comparison: PANAS Positive Affect Scoresp-value: 0.69790% CI: [0, 0.036]ANCOVA
Comparison: PANAS Negative Affect Scoresp-value: 0.46290% CI: [0, 0.053]ANCOVA
Secondary

Attrition

Attrition - to inform a future definitive trial

Time frame: 4 weeks (post-vaccination), 16 Weeks (post-vaccination)

ArmMeasureGroupCategoryValue (COUNT_OF_PARTICIPANTS)
ExperimentalAttritionAttendance at 4 Week Follow-upYes51 Participants
ExperimentalAttritionAttendance at 16 Week Follow upYes49 Participants
ExperimentalAttritionAttendance at 4 Week Follow-upNo1 Participants
ExperimentalAttritionAttendance at 16 Week Follow upNo3 Participants
Active ControlAttritionAttendance at 16 Week Follow upNo3 Participants
Active ControlAttritionAttendance at 4 Week Follow-upYes51 Participants
Active ControlAttritionAttendance at 4 Week Follow-upNo0 Participants
Active ControlAttritionAttendance at 16 Week Follow upYes48 Participants
Secondary

Health Care Utilization

Via medical records, we assessed health care usage potentially attributable to flu-like symptoms (e.g., GP visits, hospitalisation, antibiotic prescription) during the 6 months post-vaccination

Time frame: Baseline to 6 months post-vaccination

ArmMeasureGroupValue (COUNT_OF_PARTICIPANTS)
ExperimentalHealth Care UtilizationGP Consultations14 Participants
ExperimentalHealth Care UtilizationNurse Consultations1 Participants
ExperimentalHealth Care UtilizationOut of Hours/Telephone Conversations7 Participants
ExperimentalHealth Care UtilizationEmergency Department Consultations1 Participants
ExperimentalHealth Care UtilizationAntibiotic Prescriptions6 Participants
ExperimentalHealth Care UtilizationAdditional Investigations (e.g., Xray)4 Participants
Active ControlHealth Care UtilizationAntibiotic Prescriptions9 Participants
Active ControlHealth Care UtilizationGP Consultations13 Participants
Active ControlHealth Care UtilizationEmergency Department Consultations1 Participants
Active ControlHealth Care UtilizationNurse Consultations1 Participants
Active ControlHealth Care UtilizationAdditional Investigations (e.g., Xray)3 Participants
Active ControlHealth Care UtilizationOut of Hours/Telephone Conversations3 Participants
Secondary

Recruitment

Recruitment rates to inform a future definitive trial

Time frame: Baseline

Population: Total Population that received study Invitation

ArmMeasureCategoryValue (COUNT_OF_PARTICIPANTS)
ExperimentalRecruitmentExpressed Interest, but not consented23 Participants
ExperimentalRecruitmentConsented, but not randomised3 Participants
ExperimentalRecruitmentRandomised103 Participants
ExperimentalRecruitmentDid Not Express Interest1002 Participants
Secondary

Secretory IgA Response

Secretory IgA levels measured in saliva samples via ELISA. This is a non-specific measure of immunological response

Time frame: Baseline, Immediately Post Intervention (i.e, 15 minutes post-baseline).

Population: Missing Data Count n=15

ArmMeasureGroupValue (MEAN)Dispersion
ExperimentalSecretory IgA ResponsePre-Intervention Flow Rate81.0 Flow Rate (ug/min)Standard Deviation 76.4
ExperimentalSecretory IgA ResponsePost-Intervention Flow Rate116.7 Flow Rate (ug/min)Standard Deviation 107.5
Active ControlSecretory IgA ResponsePre-Intervention Flow Rate94.1 Flow Rate (ug/min)Standard Deviation 94.2
Active ControlSecretory IgA ResponsePost-Intervention Flow Rate144.7 Flow Rate (ug/min)Standard Deviation 142.5
p-value: 0.80690% CI: [0, 0.031]ANCOVA
Secondary

Vaccine Specific IgG Response

IgG levels against the 4 vaccine strains measured via ELISA. Values represent equivalent ug/ml based on diluted sample absorbance value interpolation against a standard IgG curve, multiplied by the serum dilution score (i.e., 4000).

Time frame: 4 weeks (post-vaccination), 16 Weeks (post-vaccination)

Population: Missing Data Count: n=1 for 4 weeks post-vaccination, n=5 for 16 weeks post-vaccination

ArmMeasureGroupValue (MEAN)Dispersion
ExperimentalVaccine Specific IgG Response4 Weeks Post-Vaccination A/Michigan243.28 ug/mlStandard Deviation 134.52
ExperimentalVaccine Specific IgG Response4 Weeks Post-Vaccination A/Hong-Kind301.68 ug/mlStandard Deviation 138.88
ExperimentalVaccine Specific IgG Response4 Weeks Post-Vaccination B/Brisbane126.30 ug/mlStandard Deviation 56.36
ExperimentalVaccine Specific IgG Response4 Weeks Post-Vaccination B/Phuket210.30 ug/mlStandard Deviation 123.96
ExperimentalVaccine Specific IgG Response16 Weeks Post-Vaccination A/Michigan221.69 ug/mlStandard Deviation 131.9
ExperimentalVaccine Specific IgG Response16 Weeks Post-Vaccination A/Hong-Kong283.67 ug/mlStandard Deviation 126.72
ExperimentalVaccine Specific IgG Response16 Weeks Post-Vaccination B/Brisbane139.49 ug/mlStandard Deviation 56.4
ExperimentalVaccine Specific IgG Response16 Weeks Post-Vaccination B/Phuket249.10 ug/mlStandard Deviation 124.9
Active ControlVaccine Specific IgG Response16 Weeks Post-Vaccination B/Phuket271.70 ug/mlStandard Deviation 176.16
Active ControlVaccine Specific IgG Response4 Weeks Post-Vaccination A/Michigan208.81 ug/mlStandard Deviation 122.42
Active ControlVaccine Specific IgG Response16 Weeks Post-Vaccination A/Michigan203.03 ug/mlStandard Deviation 119.41
Active ControlVaccine Specific IgG Response4 Weeks Post-Vaccination A/Hong-Kind284.96 ug/mlStandard Deviation 138.64
Active ControlVaccine Specific IgG Response16 Weeks Post-Vaccination B/Brisbane144.47 ug/mlStandard Deviation 76.77
Active ControlVaccine Specific IgG Response4 Weeks Post-Vaccination B/Brisbane127.25 ug/mlStandard Deviation 63.93
Active ControlVaccine Specific IgG Response16 Weeks Post-Vaccination A/Hong-Kong288.75 ug/mlStandard Deviation 180.18
Active ControlVaccine Specific IgG Response4 Weeks Post-Vaccination B/Phuket229.57 ug/mlStandard Deviation 135.63
Comparison: 4 Weeks A/Hong-Kongp-value: 0.43890% CI: [0, 0.055]ANCOVA
Comparison: A/Hong-Kong 16 Weeks Post-Vaccinationp-value: 0.51690% CI: [0, 0.051]ANCOVA
Comparison: A/Michigan 4 weeks post-vaccinationp-value: 0.67190% CI: [0, 0.038]ANCOVA
Comparison: A/Michigan 16 weeks post-vaccinationp-value: 0.9890% CI: [0, 0]ANCOVA
Comparison: B/Brisbane 4 weeks post-vaccinationp-value: 0.40990% CI: [0, 0.057]ANCOVA
Comparison: B/Brisbane 16 weeks post-vaccinationp-value: 0.37790% CI: [0, 0.062]ANCOVA
Comparison: B/Phuket 4 weeks post-vaccinationp-value: 0.89290% CI: [0, 0.008]ANCOVA
p-value: 0.42690% CI: [0, 0.058]ANCOVA

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026