Willingness to participate in trials
and to be vaccinated with new
tuberculosis vaccines in HIV infected adults
Dr Tendesayi Kufa
Background
• New TB vaccines are needed to meet global
targets for TB control
• HIV-infected individuals are an important target
population for new vaccines
• At least three vaccine candidates in phase I/II
trials involving people with HIV
• Phase III trials will require large numbers of
participants
• Little data on willingness to participate in TB
vaccine trials and to be vaccinated with newly
licenced vaccine
Objectives
• Describe willingness to participate in TB
vaccine trials among HIV-infected in care
• Describe willingness to be vaccinated with
newly licenced TB vaccine
• Determine factors associated with the
willingness
Methods- design and setting
• Design
• Cross-sectional design
• Context
• Vaccine preparedness study to estimate TB incidence
in HIV+ with high CD4 counts
• Setting
• 2 primary care clinics in Ekurhuleni North sub-district
Gauteng
Methods – eligibility criteria
• Inclusion criteria
•
•
•
•
•
Known HIV positive
CD4 counts >300 cells/µl in preceding 12 months
Living or working in catchment area of clinic
18 years or older
Willing and able to give consent
• Exclusion
• Acutely ill
• Pregnant (enrolled but not followed up)
Methods- study procedures
• Patients invited to take part at point of
registration for HIV care
• Questionnaires with questions on demographics,
TB and HIV history, TB knowledge and perception
of risk administered
• One questionnaire contained two Likert type
scales with 5 and 6 items respectively to measure
willingness
Methods – measurement scales
• Items in scales selected based on factors
identified as barriers/facilitators to willingness
• for each item, responses were scored:
5=“strongly agree”, 4=“agree”, 3= “disagree” 2= “strongly
disagree” 1= “I don’t know”
• Item scores were summed to give overall score
on each scale
• Internal consistency reliability determined during
analysis by determining values of Cronbach α
• α > 0.70 considered acceptable
Willingness to participate scale, α=0.92
I would be willing to :
• take part in studies to test if a new injection to prevent
TB works or not
• let my family members take part in studies to test if a
new injection to prevent TB works or not
• let my children take part in studies to test if a new
injection to prevent TB works or not
• let my children take part in studies to test a new
injection to prevent TB if I was convinced it would work
• let my children take part in studies to test a new
injection to prevent TB even if it was painful
• let my children take part in studies to test a new
injection to prevent TB even if it made me a little sick
(like vomiting, rashes, fever)
Willingness to be vaccinated scale, α=0.69
Once a new injection to prevent TB has been shown to
work in studies, I would be willing to get it:
• If it became available at my clinic
• For my family or household members if it became
available at my clinic
• For my children if it became available at my clinic
• Even if it made me a little sick (like vomiting, rashes,
fever)
• Even if I had to pay for it
Outcomes and statistical analysis
• Outcomes
• Willingness to participate in a trial of new TB vaccine
(defined as scored ≥24 out of possible score of 30)
• Willingness to be vaccinated with new TB vaccine
(defined as scores ≥ 20 out of possible score of 25)
• Data analysis
• Descriptive statistics used to describe the population
• Univariable and multivariable binomial regression was
used to estimate prevalence ratios (PR)associated with
outcomes
Findings
Study summary
2191 screened
1352 (61.7%)
Ineligible
(96% because of low
CD4 counts )
839 (38.3%) enrolled
12 (1.4%)
Duplicate enrolments
/ missing data
827 (98.6%) analysed
771 (93.2%) responded to all 6 items
on WTP scale
765 (92.5%) responded to all 5 items
on WTV scale
Study population
Variable
Total
N=827
Age (years) , median (IQR)
35 (29- 42)
Female , n (%)
665 (80.4)
Employed , n (%)
326 (39.4)
Previous TB , n (%)
227 (27.5)
Reporting ≥1 TB symptoms , n (%)
215 (26)
On ART at enrolment , n (%)
597 (72.1)
Prior or current IPT use, n (%)
189 (22.6)
Current CTX use , n (%)
116 (14)
CD4 count (cells/µl), median (IQR)
523 (427- 659)
BMI (kg/m2), median (IQR)
24.1 (21.1- 27.8)
Identified all 4 TB symptoms, n (%)
442 (53.5)
Identified TB/HIV association, n (%)
704 (85.1)
Considered one-self at risk , n (%)
442 (53.5)
Willingness to participate in trials
• Overall WTP was 84.5%
• 63% responded “strongly agree” to all items in
the scale
• Associated with:
• Correctly identifying TB symptoms [aPR 1.10 (1.03- 1.17),
p=0.003]*
• Considering oneself at risk of TB [aPR 1.07 (1.01- 1.13),
p=0.024]*
*model adjusted for age, previous TB, IPT use, CPT use, knowledge of symptoms,
knowledge of TB/HIV association and perception of risk
Willingness to be vaccinated
• Overall willingness to be vaccinated was 92.6%
• 59% responded “strongly agree” to all items in
the scale
• Associated with:
• Being employed [aPR 1.04 (95% CI 1.01- 1.08), p=0.014]*
• Considering oneself at risk of TB [aPR 1.05 (95% CI 1.011.09), p=0.02]*
*model adjusted for employment, knowledge of symptoms, knowledge of TB/HIV
association and perception of risk
Limitations
• Hypothetical
willingness does not
translate to actual
participation
• Scales not previously
validated
• Likert scales
• Social desirability
• Uniform scale intervals
Conclusions
• WTP and willingness to be vaccinated were
high in this population
• Associated with knowledge of TB, perception
of risk and employment
• Education to improve knowledge of TB and
risk factors may increase WTP/ willingness to
be vaccinated
Acknowledgements
• Staff and patients
• Aurum
• Violet Chihota, Salome Charalambous, Gavin Churchyard
• Study team- Sarah Yates, Joseph Makhura , Marcia
Masevhe, Jessie Witkoei, Salome Mahlangu, Lebogang
Masia.
• KNCV
• Suzanne Verver, Ellen Mitchell
• Funders
• EDCTP