A vaccine literacy scale for childhood vaccines: Turkish validity and reliability vaccine literacy scale

Abstract

Objective
This methodological study aimed to establish the Turkish validity and reliability of the Vaccine Literacy Scale (VLS) for childhood vaccines.

Materials and methods
The sample consisted of 285 Turkish parents with children 0–4 years of age. Data were collected using a sociodemographic characteristics questionnaire, the VLS, and the Health Literacy Scale (HLS-14). A confirmatory factor analysis (CFA) was performed to analyze the validity of the psychometric properties. Item total score correlation, Cronbach’s coefficient (α), and parallel form reliability tests were used to analyze the reliability. The data were analyzed using the Statistical Package for Social Sciences (SPSS, IBM, v. 25) and Analysis of Moment Structures (AMOS, v. 21.0) at a significance level of 0.05.

Results
According to the CFA, the model fit indices were χ2 = 121.218, χ2/df = 1.987, RMSA = 0.059, CFI =.0.974, GFI = 0.943, and AGFI = 0.914. The item-total score correlation values ranged from 0.406 to 0.682. The “functional health literacy,” “communicative health literacy,” and “critical health literacy” subscales had Cronbach’s alpha values of 0.87, 0.88, and 0.88, respectively. There was a negative correlation between the VLS and HLS-14 (r = –0.618–0.569) (p < 0.000).

Conclusion
The analyses and evaluations show that the Vaccine Literacy Scale is valid and reliable for the Turkish population. It is a valid and reliable instrument that can be used to determine Turkish parents’ health literacy regarding childhood vaccines.

Full text

Vol.:(0123456789)
1 3
Journal of Public Health
https://doi.org/10.1007/s10389-023-01878-5
ORIGINAL ARTICLE
A vaccine literacy scale forchildhood vaccines: Turkish validity
andreliability vaccine literacy scale
DenizS.Yorulmaz1 · DenizKocoglu‑Tanyer2
Received: 28 October 2022 / Accepted: 2 March 2023
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023
Abstract
Objective This methodological study aimed to establish the Turkish validity and reliability of the Vaccine Literacy Scale
(VLS) for childhood vaccines.
Materials and methods The sample consisted of 285 Turkish parents with children 0–4 years of age. Data were collected
using a sociodemographic characteristics questionnaire, the VLS, and the Health Literacy Scale (HLS-14). A confirmatory
factor analysis (CFA) was performed to analyze the validity of the psychometric properties. Item total score correlation,
Cronbach’s coefficient (α), and parallel form reliability tests were used to analyze the reliability. The data were analyzed
using the Statistical Package for Social Sciences (SPSS, IBM, v. 25) and Analysis of Moment Structures (AMOS, v. 21.0)
at a significance level of 0.05.
Results According to the CFA, the model fit indices were χ2 = 121.218, χ2/df = 1.987, RMSA = 0.059, CFI =.0.974, GFI
= 0.943, and AGFI = 0.914. The item-total score correlation values ranged from 0.406 to 0.682. The “functional health
literacy,” “communicative health literacy,” and “critical health literacy” subscales had Cronbach’s alpha values of 0.87,
0.88, and 0.88, respectively. There was a negative correlation between the VLS and HLS-14 (r = –0.618–0.569) (p < 0.000).
Conclusion The analyses and evaluations show that the Vaccine Literacy Scale is valid and reliable for the Turkish population.
It is a valid and reliable instrument that can be used to determine Turkish parents’ health literacy regarding childhood vaccines.
Keywords Vaccination· Literacy· Health literacy· Scale· Validity· Reliability· Parents
Introduction
Vaccination is an important public health practice for protect-
ing and promoting health and preventing infectious diseases
(World Health Organization (WHO), Global Vaccine Action
Plan 2020). Vaccination provides artificial immunity by intro-
ducing weakened or killed bacteria and/or viruses into the
living body. Vaccination provides both individual and herd
immunity. Vaccination also significantly reduces the incidence
and prevalence of infectious diseases, mortality rates, eco-
nomic losses, and disability (Ergür 2020; Al-Regaiey etal.
2022). According to the WHO, 100 million children are vac-
cinated before one year, preventing 2–3 million child deaths
annually (WHO 2019; Yıldızeli etal. 2021).
Vaccine refusal has risen globally for the past ten years
despite known vaccine efficacy. According to the WHO, nine
out of ten children had access to vaccines, but there were 20
million unvaccinated children in 2019. Moreover, it has been
reported that vaccine refusal is rising (WHO Global Vaccine
Action Plan 2020). Vaccine refusal is also on the rise in Tur-
key. Childhood immunization rates have declined since 2008
(TNSA 2018). In 2011, 183 Turkish families refused to vac-
cinate their children due to vaccine hesitancy. However, this
number increased to 12,000 in 2016, 23,000 in 2018, and
40,000 in 2019 (Aygün and Tortop 2020). Vaccine refusal in
Turkey increased 125-fold between 2012 and 2019 (Erdoğan
etal. 2021). The WHO established the Strategic Advisory
Group of Experts on Immunization (SAGE) in response to
the global rise in vaccine refusal. SAGE has conducted con-
siderable research on vaccine hesitancy and refusal (Betsch
etal. 2018; MacDonald 2015).
* Deniz S. Yorulmaz
denizyrlmz.20144@gmail.com
Deniz Kocoglu-Tanyer
deniizkocoglu@gmail.com
1 Faculty ofHealth Sciences, Nursing Depertmant, Artvin
Çoruh University, Artvin, Turkey
2 Department ofPublic Health, Faculty ofNursing, Selcuk
University, Konya, Turkey

Journal of Public Health
1 3
If vaccine refusal rates continue to grow, immunization
rates are projected to fall below 80% in the next five years,
resulting in epidemics and deaths from childhood diseases,
which are a thing of the past (Nas etal. 2020). We must pre-
vent vaccine hesitancy and refusal and improve information
and vaccine literacy to protect and sustain public health and
prevent infectious diseases (Jones etal. 2012).
Vaccine literacy is based on health literacy. It is
defined as the degree to which one can obtain, process,
and understand the information that underlies the enor-
mously complex data involved in vaccine science (Biasio
etal. 2020). Everyone should have a certain level of vac-
cine literacy because vaccine technology is complicated
(Yıldızeli etal. 2021). People have difficulty accessing
the right information and making informed decisions
because misinformation and conspiracy theories about
vaccines are swirling around online (Yıldızeli etal. 2021).
Vaccine literacy is a complex concept that is crucial for
the prevention of vaccine hesitancy and refusal. Vaccine
literacy is concerned with assessing vaccine knowledge,
training and interventions regarding vaccines, and nursing
care (Biasio etal. 2020).
Vaccine literacy is an important issue affecting vaccina-
tion intention. It is a critical tool for preventing diseases
and protecting and improving public health (Ratzan and
Parker 2020). We cannot battle against vaccine hesitancy
and refusal without assessing vaccine literacy (Lorini etal.
2022; Montagni etal. 2019; Vanderslott andMarks 2021).
Valid and reliable measurement tools can help us assess vac-
cine literacy, identify the factors affecting it, and formulate
interventions to increase it (Aharon etal. 2017). However,
there are no valid and reliable scales in Turkish for vaccine
literacy. Therefore, this study aimed to establish the Turkish
validity and reliability of the Vaccine Literacy Scale (VLS)
for childhood vaccines.
Materials andmethods
Research purpose anddesign
This study adopted a methodological design to adapt the
VLS into Turkish.
Population andsample
The Vaccine Literacy Scale was developed by Aharon
etal. (2017) to assess parents’ health literacy regarding
childhood vaccines. The study population consisted of
all parents of children 0–4 years of age because Turkey
administers 17 of the 20 vaccines in the first 48 months of
life according to the Childhood Vaccination Schedule of
the Ministry of Health. A common rule of thumb for scale
development is to have a sample size of five to ten times
the number of items on the scale (Seçer 2017). However,
a common rule of thumb for scale adaptation is to have a
sample size of five to 20 times the number of items on the
scale. The Vaccine Literacy Scale consists of 13 items. A
sample of 65 to 130 participants would be large enough
to develop a scale. However, the sample size should be
at least 250–300 participants to satisfy the assumptions
of multiple normal distributions in confirmatory factor
analysis (CFA). Therefore, the final sample consisted of
285 parents of children 0–4 years of age.
Research steps
This study adhered to the principles of the International
Test Commission (ITC) Guidelines for Translating and
Adapting Tests (Gregoire 2018). First, the researchers
obtained authorization from the developers of the scale.
Second, a translation center with an international quality
certificate translated the scale into Turkish. Third, the
researchers sent the Turkish version to 19 experts with
a Ph.D. in public health nursing and pediatric nursing.
They received feedback from 13 experts about the lan-
guage validity of the scale. They made modifications to
the items based on expert feedback. They conducted a
pilot study with 30 parents of children 0–4 years of age.
None of the participants gave negative feedback about
the intelligibility of the items. Afterward, the researchers
collected data. After data collection, they assessed the
psychometric properties of the scale. They then finalized
the scale and established its directive.
Steps oftheadaptation oftheVLS toTurkish
• Receiving authorization from the developers of the scale
• Having the scale translated into Turkish by the translation
center
• Receiving expert feedback and developing a draft
• Conducting a pilot study and assessing feedback
• Developing the draft scale
• Translating the scale back into English and receiving the
approval of its developers
• Assessing the psychometric properties of the scale (valid-
ity and reliability)
Validity analysis Confirmatory factor analysis
Reliability analysis Cronbach’s (α) reliability coefficient,
item-total score correlation, and parallel form reliability
• Finalizing the scale and developing its directive

Journal of Public Health
1 3
Data collection tools
The data were collected using a sociodemographic charac-
teristics questionnaire, the VLS, and the Health Literacy
Scale (HLS-14).
Sociodemographic characteristics questionnaire
The sociodemographic characteristics questionnaire was
based on a literature review conducted by the researchers
(Aharon etal. 2017; Jones etal. 2012; Nas etal. 2020).
The questionnaire consisted of ten items: age, education,
spousal education, family income, number of children, get-
ting childhood vaccinations regularly, thoughts on childhood
vaccinations, etc.
Vaccine literacy scale
The Vaccine Literacy Scale was developed based on the
HLS-14 by Aharon etal. (2017) to assess parents’ literacy on
childhood vaccinations. The scale consists of 13 items and
three subscales: functional health literacy (five items), com-
municative health literacy (five items), and critical health
literacy (three items). The items are rated on a four-point
Likert-type scale (1 Never, 2 Sometimes, 3 Often, 4 Most
of the time). The scores of the subscales are calculated sepa-
rately; therefore, the scale has no total score. Responses in
each subscale are divided by the number of items to obtain a
score. Lower functional health literacy scores indicate higher
health literacy. Higher communicative and critical health
literacy scores indicate higher health literacy. The “func-
tional health literacy,” “communicative health literacy,” and
“critical health literacy” subscales have Cronbach’s alpha
values of 0.70, 0.66, and 0.81, respectively (Aharon etal.
2017). The researchers emailed the developers to establish
the Turkish validity and reliability of the scale.
Health Literacy Scale (HLS‑14)
The Health Literacy Scale (HLS-14) was developed by Suka
etal. (2013) for Japanese adults. The scale consists of 14
items and three subscales: functional health literacy (five
items; α = 0.83), interactive health literacy (five items; α
= 0.85), and critical health literacy (four items; α = 0.76).
The total scale has a Cronbach’s alpha of 0.81. The items
are rated on a five-point Likert-type scale (1 Strongly Disa-
gree, 2 Disagree, 3 Undecided, 4 Agree, 5 Strongly Agree).
The “functional health literacy” subscale items are reverse
scored. The total score ranges from 14 to 70, with higher
scores indicating higher health literacy. The scale was
adapted into Turkish by Türkoğlu and Kılıç (2021). The
Turkish version also consists of 14 items and three sub-
scales: functional health literacy (five items; α = 0.85),
interactive health literacy (five items; α = 0.90), and critical
health literacy (four items; α = 0.87). The total scale has a
Cronbach’s alpha of 0.85. The results show that the HLS-
14 is a valid and reliable scale for the Turkish population
(Türkoğlu and Kılıç 2021). In this study, the “functional
health literacy,” “interactive health literacy,” and “critical
health literacy” subscales had Cronbach’s alpha values of
0.91, 0.90, and 0.87, respectively. The total scale had a Cron-
bach’s alpha of 0.89.
Data collection
The study was conducted between 25.05.2022 and
25.06.2022. The data were collected both face-to-face and
online to recruit as many participants as possible. The online
data were collected through Google Forms. All parents were
sent a link to the survey through social media platforms
(Gmail, WhatsApp, Facebook, Instagram, etc.). All parents
were briefed about the research purpose and procedure.
Informed consent was obtained from those who agreed to
participate. One hundred and forty-eight participants filled
out the online survey. The face-to-face data were collected
from parents admitted to a family health center. Those par-
ents were invited to the study. Informed consent was obtained
from those who agreed to participate. One hundred and
thirty-seven participants filled out the survey. It took each
participant 3–4 min to fill out the survey. The researchers
answered all questions that the participants had in mind.
Data analysis
The data were analyzed using the Statistical Package for the
Social Sciences (SPSS, v.23) and Analysis of Moment Struc-
tures (AMOS, v.23) at a significance level of 0.05. Numbers
and percentages were used for descriptive statistics. Valid-
ity was assessed using CFA and fit indices [Chi-square
(CMIN), Minimum Discrepancy Function by Degrees of
Freedom Divided (CMINDF/df), Root Mean Square Error
of Approximation (RMSEA), Goodness of Fit Index (GFI),
Comparative Fit Index (CFI), Normed Fit Index (NFI),
Tucker–Lewis index (TLI), and Adjusted Composite Finan-
cial Index (AGFI)]. Reliability was assessed using item-total
score correlation, Cronbach’s alpha reliability coefficient,
and parallel form.
Results
More than half of the participants had bachelor’s degrees
(55.4%). Most participants had nuclear families (83.2%).
Less than half of the participants had a neutral income
(income = expense). Most participants had health cover-
age (87.4%). Most participants had their children vaccinated

Journal of Public Health
1 3
according to the national immunization schedule (90.2%)
and believed that childhood vaccinations were necessary
and useful (84.2%) (Table1). Participants had mean HLS-
14 “functional health literacy,” “communicative health
literacy,” and “critical health literacy” subscale scores of
18.5±5.7 (min 5, max 25), 21.3±5.7 (min 5, max 25), and
17.3±3.0 (min 5, max 25), respectively. They had a mean
total HLS-14 score of 57.2±10.0 (min 23, max 70).
Confirmatory factor analysis
A confirmatory factor analysis was performed to determine
the validity of the VLS for the Turkish population. First,
sample adequacy was examined using the Holter value dur-
ing the CFA analysis. The results showed that a sample of
188 was large enough at a significance level of 0.05, while
a sample of 210 was large enough at a significance level of
0.01. Therefore, it was concluded that a sample of 285 was
large enough. The maximum likelihood calculation method
was used because the data were normally distributed. The
scale items had factor loadings of 0.64 to 0.90, suggesting
that the subscales and the items contributed to the scale ade-
quately. χ2/df, CFI, and NFI had a perfect fit for the data,
while GFI, AGFI, and RMSEA had an acceptable fit for the
data (χ2 = 121.218, χ2/df = 1.987, RMSA = 0.059, CFI =
0.974, GFI = 0.943, AGFI= 0.914) (Table2).
Reliability
Reliability was assessed using item-total score correlation,
Cronbach’s alpha reliability coefficient, and parallel form.
Item‑total score correlation
Table3 shows the item-total score correlation test results.
The items had correlation coefficients of 0.406 to 0.682
(Table3).
Cronbach’s alpha reliability coefficient
The “functional health literacy,” “communicative health
literacy,” and “critical health literacy” subscales had Cron-
bach’s alpha values of 0.877, 0.886, and 0.882, respectively.
There was no increase in Cronbach’s alpha when any item
was deleted (Table4).
Parallel form reliability
The Pearson correlation coefficient was used to determine
the correlation between the VLS and the HLS-14 (Table5).
The HLS-14 total score, each VLS subscale, and the same
subscales in both scales were evaluated. There was a mod-
erate correlation between the VLS and HLS-14 subscales.
Table 1 Sociodemographic characteristics (n = 285)
Sociodemographic characteristics n %
Age (year) 34.7±6.6 (Min 19, Max 58)
Number of children 1.94±1.00 (Min 1, Max 5)
Education (degree)
Primary school
Middle school
High school
Bachelor’s
34
26
67
158
11.9
9.1
23.5
55.5
Spouse’s education (degree)
Primary school
Middle school
High school
Bachelor’s
24
43
68
150
8.4
15.1
23.9
52.6
Family type
Nuclear
Extended
Single parent
237
38
10
83.2
13.3
3.5
Employment status
Housewife
Employed
136
149
47.7
52.3
Family income
Negative income (income < expense)
Neutral income (income = expense)
Positive income (income > expense)
87
136
62
30.5
47.7
21.8
Health coverage
Yes
No
249
36
87.4
12.6
Childhood vaccinations
Regular and complete
Missing
None
257
27
1
90.1
9.5
0.4
Thoughts on childhood vaccinations
All vaccines are useful and necessary
Vaccines are useful but all are necessary
Vaccines are unnecessary
No idea
240
37
2
6
84.2
13.0
0.7
2.1
Table 2 Confirmatory factor analysis of the Vaccine Literacy Scale
for childhood vaccines
χ2, Chi-square, sd, Degrees of freedom, χ2/sd, Chi-square/degrees
of freedom, GFI, Goodness of Fit Index, AGFI, Adjusted Goodness
of Fit Index, CFI, Comparative Fit Index, RMSEA, Root mean square
error of approximation, RMR, Root mean square residual, NFI, Nor-
med Fit Index (Assessment was conducted in the default model)
Fit indices estimates Acceptable fit Perfect fit Scale values
X2/sd <5 <2 1.987
GFI >0.90 >0.95 0.943
AGFI >0.90 >0.95 0.914
CFI >0.90 >0.95 0.974
RMSEA <0.05 <0.08 0.059
RMR <0.05 <0.08 0.030
NFI >0.90 >0.95 0.95

Journal of Public Health
1 3
There was also a moderate correlation between the total
HLS-14 score and VLS subscale scores (Table5).
Discussion
After clean water and sanitation, vaccination is the most
effective method for protecting and promoting health and
preventing infectious diseases. Globally, vaccines prevent
many infant and child deaths each year and significantly
reduce disability (WHO Global Vaccine Action Plan 2020).
Despite known vaccine efficacy, vaccine hesitancy and
refusal are rising, increasing infant and child mortality
rates globally. Twenty-eight participants (9.9%) had chil-
dren who had missed some vaccines (n = 27) or had never
been vaccinated (n = 1). This rate ranges from 11.7% to
21.3% in the United States, Albania, Canada, Romania, etc.
(Edwards and Hackell 2016; Dubé etal. 2015; Mayerova
and Abbas 2021; Miko etal. 2019). SAGE makes the fol-
lowing recommendations: First, we must develop valid and
reliable measurement tools to combat vaccine hesitancy and
refusal. Second, healthcare professionals should determine
people’s vaccine literacy and formulate interventions to help
them adopt it (Eskola etal. 2015). Research shows that peo-
ple with higher vaccine literacy are less likely to hesitate
Table 3 The results of item total
score correlation test Item No Item correlation Item No Item correlation Item No Item correlation
1 0.406 6 0.589 11 0.631
2 0.476 7 0.682 12 0.600
3 0.525 8 0.638 13 0.617
4 0.473 9 0.586
5 0.439 10 0.643
Table 4 Reliability analysis of Vaccine Literacy Scale for childhood
vaccines (n = 285)
Item no Mean Standard
deviation
Cronbach’s
alpha (α)
Cronbach’s alpha (α)
when an item deleted
Functional health literacy subscale
Item 1 3.05 0.98 0.877 0.871
Item 2 2.90 1.05 0.845
Item 3 3.13 0.93 0.829
Item 4 3.09 1.00 0.835
Item 5 3.51 0.86 0.873
Communicative health literacy subscale
Item 6 3.05 1.02 0.886 0.861
Item 7 3.15 0.96 0.849
Item 8 3.27 0.88 0.872
Item 9 3.32 0.88 0.867
Item 10 3.30 0.86 0.857
Critical health literacy subscale
Item 11 3.33 0.87 0.882 0.815
Item 12 3.26 0.88 0.799
Item 13 3.48 0.76 0.877
Table 5 Correlation between
VLS and HLS-14 (n = 285)
**Significance level 0.01
HLS-14
Functional
health literacy
Communicative
health literacy
Critical health
literacy
Total
VLS Functional health literacy
Pearson correlation (r) –0.618** –0.523**
p 0.000 0.000
n 285 285
Communicative Health Literacy
Pearson correlation (r) 0.569** 0.550**
p 0.000 0.000
n 285 285
Critical health literacy
Pearson correlation (r) 0.458** 0.553**
p 0.000 0.000
n 285 285

Journal of Public Health
1 3
or refuse to get vaccinated or get their children vaccinated
(Baysan etal. 2021; Dubé etal. 2015). Therefore, we should
assess people’s vaccine literacy to combat vaccine hesitancy
and refusal. A psychometric measurement tool must be valid
and reliable. Otherwise, it cannot measure the construct it
is intended to measure (Seçer 2017). This study established
the Turkish validity and reliability of the VLS for the Turk-
ish population.
Validity
Validity is the extent to which an assessment accurately
measures what it intends to measure. Validity is the most
important feature that a measurement tool should have. A
measurement tool that is not valid fails to yield accurate
results even if it is reliable (Alpar 2006). Construct validity
is a popular method for assessing the validity of a meas-
urement tool. Construct validity is the degree to which a
measurement tool can measure the theoretical construct it
is intended to measure. Factor analysis (exploratory factor
analysis and/or confirmatory factor analysis) should be used
to assess construct validity (Seçer 2017). In this study, a
CFA was performed to establish the construct validity of
the VLS. Confirmatory factor analysis is a type of struc-
tural equation modeling used to examine whether the factor
structure of a measurement instrument is consistent with
theoretical knowledge (Çapık 2014). Confirmatory factor
analysis focuses on fit indices such as χ2, χ2/sd, GFI, AGFI,
RMSEA, RMR, SRMR, NFI, and TLI. An x2/sd value of
≤ 2 indicates an excellent fit. An x2/sd value of ≤ 5 indi-
cates an acceptable fit. A GFI, CFI, AGFI, and NFI greater
than 0.95 indicate an excellent fit. An RMSEA and RMR
smaller than 0.05 indicate an excellent fit. An RMSEA and
RMR smaller than 0.08 indicate an acceptable fit (Boateng
etal. 2018; Çapık 2014; Yaşlıoğlu 2017). In this study, x2/
sd (1.987), GFI (0.943), AGFI (0.914), CFI (0.974), NFI
(0.95), RMSEA (0.059), and RMR (0.030) were acceptable.
x2/sd, CFI, NFI, and RMR indicated an excellent fit. In con-
firmatory factor analysis, a scale should consist of items with
factor loadings greater than 0.45. Moreover, items should
have high loadings on a single factor and low loadings on
others (Büyüköztürk 2010; Sönmez and Alacapınar 2016).
Our CFA results showed that all items had factor loadings
greater than 0.45, ranging from 0.64 to 0.90 (Fig.1). The
CFA results were consistent with the literature. The sub-
scales were consistent with the scale. All items were ade-
quately correlated with their subscales. These results show
that the VLS is a valid instrument for the Turkish population.
Reliability
Reliability is a fundamental characteristic of a measure-
ment tool. A reliable instrument yields consistent results
over time that are free from errors. The lower the error rate
of a measurement tool, the more reliable it is (Boateng etal.
2018). Different methods (Cronbach’s alpha coefficient,
Fig. 1 The figure of confirma-
tory factor analysis

Journal of Public Health
1 3
Kuder–Richardson 20–21, etc.) are used to determine the
reliability of instruments measuring cognitive and affec-
tive characteristics. However, Cronbach’s alpha is used to
assess the internal consistency of scales with items rated on
Likert-type scales. A Cronbach’s alpha of 0.00 ≤ α ≤ 0.40
indicates unreliability. A Cronbach’s alpha of 0.40 ≤ α ≤
0.60 indicates low reliability. A Cronbach’s alpha of 0.60
≤ α ≤ 0.80 indicates reliability. A Cronbach’s alpha of 0.80
≤ α ≤ 1.00 indicates high reliability (Boateng etal. 2018).
A reliable instrument should have a Cronbach’s alpha of at
least 0.70. The higher the Cronbach’s alpha, the more reli-
able the instrument (Karakoç and Dönmez 2014; Terwee
etal. 2007). In this study, the “functional health literacy,”
“communicative health literacy,” and “critical health liter-
acy” subscales had Cronbach’s alpha values of 0.87, 0.88,
and 0.88, respectively. These results show that the VLS is a
highly reliable instrument.
Item‑total score correlation
An item-total correlation value refers to the correlation
between the scale and total scores. The higher the correlation
coefficient for each item, the more effectively and adequately
it can measure the concept, situation, and/or construct it
intends to measure. An item must have a correlation coeffi-
cient of at least 0.32. Items with correlation coefficient values
smaller than 0.32 should be removed from the scale. Items
with item correlation value greater than 0.90 should also be
removed from the scale because they measure the same con-
cept, situation, and/or construct (Çokluk 2010). The Vaccine
Literacy Scale had item-total correlation values of 0.40 to
0.68. None of the items had an item-total correlation value
smaller than 0.32 or greater than 0.90 (Table3). The results
show that the scale items can measure the concept, situation,
and/or construct they are intended to measure.
Parallel form reliability
Parallel form reliability involves administering two similar,
but not the same, versions of an instrument and correlating
the scores. The correlation coefficient (r) examines the rela-
tionship between two continuous variables (Seçer 2017). The
correlation coefficient ranges from –1 to +1. The Pearson
correlation coefficient measures the strength of a linear asso-
ciation between two variables when data is normally distrib-
uted. Spearman’s rank correlation coefficient measures the
strength of a linear association between two variables when
data is non-normally distributed. A scale is reliable if the
correlation coefficient is significant (0.00 ≤ r ≤ 0.19 very
weak; 0.20 ≤ r ≤ 0.39 weak; 0.40 ≤ r ≤ 0.69 moderate; 0.70
≤ r ≤ 0.89 strong; 0.90 ≤ r ≤ 1.00 very strong) (Ersöz and
Ersöz 2019). In this study, the HLS-14 was used to determine
the parallel form reliability of the VLS. The HLS-14 was the
scale of choice because it assesses adults’ health literacy and
has subscales similar to those of the VLS (functional, com-
municative, and critical health literacy). The Pearson correla-
tion coefficient was used to determine parallel form reliabil-
ity because the data were normally distributed. The results
showed a moderate correlation between the HLS-14 and
the VLS subscales. A moderate correlation was also found
between the HLS-14 total score and the VLS subscale scores.
The VLS “functional health literacy” had a negative corre-
lation because its items are reverse scored. It is no surprise
that the scales have a moderate correlation. Researchers have
developed more focused scales on nutrition, environmental,
and e-health literacy because health behavior-specific literacy
falls short of explaining general health literacy (Atabek Yiğit
etal. 2014; Çoşkun and Bebiş 2015; Sonay Türkmen etal.
2017). These results show that the VLS is reliable for assess-
ing parents’ childhood vaccine literacy.
Conclusion
The Vaccine Literacy Scale is a valid and reliable instrument
for assessing Turkish parents’ childhood vaccine literacy. It
consists of 13 items and three subscales. Healthcare profes-
sionals can use the VLS to determine parents’ health lit-
eracy regarding childhood vaccines, assess the effectiveness
of training on childhood vaccines, and plan relational and/
or interventional interventions to prevent vaccine hesitancy
and refusal. Public health experts and policymakers should
use the VLS to plan interventions to protect, promote, and
sustain public health. The scale will allow researchers to
make regional comparisons of parents’ childhood vaccine
literacy at the national level. It will also help them compare
parents’ childhood vaccine literacy internationally.
Ethical considerations
Authorization was obtained from the developers to adapt
the VLS into Turkish. The study was approved by the ethics
committee of Artvin Çoruh University (No: E-18457941-
050.99-45390 & Date: 05.04.22). Prior to the study, the
institution’s permit was taken (Issue: E-17720518-605.99).
All parents were briefed about the research purpose and
procedure. Informed consent was obtained from those who
agreed to participate. The research was conducted accord-
ing to the ethical principles of the Declaration of Helsinki.

Journal of Public Health
1 3
Author contributions All authors contributed to the study conception
and design. Material preparation, data collection and analysis were
performed by Deniz S. Yorulmaz and Deniz Kocoglu-Tanyer. The first
draft of the manuscript was written by Deniz S. Yorulmaz and Deniz
Kocoglu-Tanyer listed as co-first authors. Supervision and consul-
tancy was carried out by Deniz Kocoglu-Tanyer. All authors read and
approved the final manuscript.
Data availability Data that supports the finding of this article are avail-
able from the corresponding author (DSY) upon reasonable request.
Code availability Not applicable.
Declarations
Ethics committee approval Artvin Çoruh University (No: E-18457941-
050.99-45390 & Date: 05.04.22). The institution’s permit Issue:
E-17720518-605.99.
Informed consent Informed consent was obtained from those who
agreed to participate.
Conflict of interest The authors declare that they have no conflicts of
interest.
References
Aharon AA, Nehama H, Rishpon S, Baron-Epel O (2017) Parents with
high levels of communicative and critical health literacy are less
likely to vaccinate their children. Patient Educ Couns 100(4):768–
775. https:// doi. org/ 10. 1016/j. pec. 2016. 11. 016
Alpar R (2006) Spor bilimlerinde uygulamalı istatislik. Ankara, Turkey
Al-Regaiey KA, Alshamry WS, Alqarni RA, Albarrak MK, Alghoraiby
RM, Alkadi DY, Iqbal M (2022) Influence of social media on par-
ents’ attitudes towards vaccine administration. Human Vaccines
& Immunotherapeutics 18(1):1872340. https:// doi. org/ 10. 1080/
21645 515. 2021. 18723 40
Atabek-Yiğit E, Köklükaya N, Yavuz M, Demirhan E (2014) Devel-
opment and validation of environmental literacy scale for adults
(ELSA). J Balt Sci Educ 13(3):425–435
Aygün E, Tortop HS (2020) Ebeveynlerin aşı tereddüt düzeylerinin ve
karşıtlık nedenlerinin incelenmesi. Güncel Pediatri 18(3):300–316
Baysan C, Yavaş SP, Karabat MU (2021) Examination of parents refus-
ing administration of childhood vaccinations: Turkey example.
Childs. Health 16(3):218–224. https:// doi. org/ 10. 22141/ 2224-
0551. 16.3. 2021. 233906
Betsch C, Schmid P, Heinemeier D, Korn L, Holtmann C, Böhm R
(2018) Beyond confidence: Development of a measure assess-
ing the 5C psychological antecedents of vaccination. PLoS One
13(12):e0208601. https:// doi. org/ 10. 1371/ journ al. pone. 02086 01
Biasio LR, Giambi C, Fadda G, Lorini C, Bonaccorsi G, D’Ancona F
(2020) Validation of an Italian tool to assess vaccine literacy in
adulthood vaccination: A pilot study. Ann Ig 32:205–222. https://
doi. org/ 10. 7416/ ai. 2020. 2344
Boateng GO, Neilands TB, Frongillo EA, Melgar-Quiñonez HR,
Young SL (2018) Best practices for developing and validating
scales for health, social, and behavioral research: a primer. Front
Public Health 6:149. https:// doi. org/ 10. 3389/ fpubh. 2018. 00149
Büyüköztürk Ş (2010) Sosyal bilimler için veri analizi el kitabı.
Ankara, Turkey
Çapik C (2014) Geçerlik ve güvenirlik çalişmalarinda doğrulayici fak-
tör analizinin kullanimi. Anadolu Hemşirelik ve Sağlık Bilimleri
Dergisi 17(3):196–205
Çokluk Ö (2010) Lojistik Regresyon analizi: kavram ve uygulama.
Edvtcational Sciences: Theot & Practice. 10(3):1357–1407
Coşkun S, Bebiş H (2015) Adolesanlarda e-sağlık okuryazarlığı ölçeği:
Türkçe geçerlik ve güvenirlik çalışması. Gülhane Tıp Dergisi
57(4):378–384. https:// doi. org/ 10. 5455/ gulha ne. 157832
Dubé E, Vivion M, MacDonald NE (2015) Vaccine hesitancy, vac-
cine refusal and the anti-vaccine movement: influence, impact and
implications. Expert Review of Vaccines 14(1):99–117. https://
doi. org/ 10. 1586/ 14760 584. 2015. 964212
Edwards KM, Hackell JM (2016) Countering vaccine hesitancy. Pedi-
atrics 138(3):e20162146. https:// doi. org/ 10. 1542/ peds. 2016- 2146
Erdoğan A, Güven K, Şahin AR, Okyay RA (2021) Understanding the
approach of family physicians in Turkey to the problem of vaccine
rejection. Human Vaccines & Immunotherapeutics 17(6):1693–
1698. https:// doi. org/ 10. 1080/ 21645 515. 2020. 18433 35
Ergür A (2020) Social causes of vaccine rejection-vaccine indecision
attitudes in the context of criticisms of modernity. Eurasian J Med
52(2):217–23. https:// doi. org/ 10. 5152/ euras ianjm ed. 2020. 20132
Ersöz F, Ersöz T (2019) SPSS ile istattistiksel veri analizi. Ankara,
Tukey
Eskola J, Duclos P, Schuster M, MacDonald NE (2015) How to deal
with vaccine hesitancy? Vaccine 33(34):4215–4217. https:// doi.
org/ 10. 1016/j. vacci ne. 2015. 04. 043
Gregoire J (2018) ITC guidelines for translating and adapting tests. Int
J Test 18(2):101–134
Jones AM, Omer SB, Bednarczyk RA, Halsey NA, Moulton LH,
Salmon DA (2012) Parents’ source of vaccine information and
impact on vaccine attitudes, beliefs, and nonmedical exemptions.
Advances in Preventive Medicine 2012. Article ID:932741, 8
pages. https:// doi. org/ 10. 1155/ 2012/ 932741
Karakoç FY, Dönmez L (2014) Ölçek geliştirme çalışmalarında temel
ilkeler. Tıp Eğitimi Dünyası 13(40):39–49. https:// doi. org/ 10.
25282/ ted. 228738
Lorini C, Collini F, Galletti G, Ierardi F, Forni S, Gatteschi C, Bonac-
corsi G (2022) Vaccine Literacy and Source of Information about
Vaccination among Staff of Nursing Homes: A Cross-Sectional
Survey Conducted in Tuscany (Italy). Vaccines 10(5):682. https://
doi. org/ 10. 3390/ vacci nes10 050682
MacDonald NE (2015) Vaccine hesitancy: Definition, scope and deter-
minants. Vaccine 33(34):4161–4164. https:// doi. org/ 10. 1016/j.
vacci ne. 2015. 04. 036
Mayerová D, Abbas K (2021) Childhood immunisation timeliness and
vaccine confidence by health information source, maternal, socio-
economic, and geographic characteristics in Albania. BMC Public
Health 21(1):1–17. https:// doi. org/ 10. 1186/ s12889- 021- 11724-6
Miko D, Costache C, Colosi HA, Neculicioiu V, Colosi IA (2019)
Qualitative assessment of vaccine hesitancy in Romania. Medicina
55(6):282. https:// doi. org/ 10. 3390/ medic ina55 060282
Montagni I, Cariou T, Tzourio C, González-Caballero JL (2019) “I
don’t know”,“I’m not sure”,“I don’t want to answer”: a latent class
analysis explaining the informative value of nonresponse options
in an online survey on youth health. Int J Soc Res Methodol
22(6):651–667. https:// doi. org/ 10. 1080/ 13645 579. 2019. 16320 26
Nas MA, Atabay G, Şakiroğlu F, Cayir Y (2020) Vaccine Rejection in
A University’s Training Family Health Centers. Konuralp Medi-
cal Journal 12(3):430–434. https:// doi. org/ 10. 18521/ ktd. 744687
Ratzan SC, Parker RM (2020) Vaccine literacy—helping everyone
decide to accept vaccination. J Health Commun 25(10):750–752.
https:// doi. org/ 10. 1080/ 10810 730. 2021. 18750 83
Seçer İ (2017) SPSS ve LISREL ile pratık veri analizi. Ankara, Turkey
Sonay Türkmen A, Kalkan İ, Filiz E (2017) Adolesan beslenme
okuryazarlığı ölçeğinin türkçe’ye uyarlanması: geçerlilik ve
güvenilirlik çalışması. International Peer-Reviewed Journal of

Journal of Public Health
1 3
Nutrition Research 10:1–20. https:// doi. org/ 10. 17362/ DBHAD.
2017.2. 01
Sönmez V, Alacapınar FS (2016) Sosyal bilimlerde ölçme aracı
hazırlama. Ankara, Turkey
Suka M, Odajima T, Kasai M, Igarashi A, Ishikawa H, Kusama M,
Sugimori H (2013) The 14-item health literacy scale for Japa-
nese adults (HLS-14). Environ Health Prev Med 18(5):407–415.
https:// doi. org/ 10. 1007/ s12199- 013- 0340-z
Terwee CB, Bot SD, de Boer MR, van der Windt DA, Knol DL, Dekker
J, de Vet HC (2007) Quality criteria were proposed for measure-
ment properties of health status questionnaires. J Clin Epidemiol
60(1):34–42. https:// doi. org/ 10. 1016/j. jclin epi. 2006. 03. 012
Türkiye Nüfus ve Sağlık Araştırması (2018) www. sck. gov. tr/ wp- conte
nt/ uploa ds/ 2020/ 08/ TNSA2 018_ ana_ Rapor. pdf
Türkoğlu N, Kılıc D (2021) Sağlık okuryazarlığı ölçeği’nin Türkçe’ye
uyarlanması: geçerlilik ve güvenilirlik çalışması. Anadolu
Hemşirelik ve Sağlık Bilimleri Dergisi 24(1):25–33. https:// doi.
org/ 10. 17049/ ataun ihem. 662054
Vanderslott S, Marks T (2021) Charting mandatory childhood vaccina-
tion policies worldwide. Vaccine 39(30):4054–4062. https:// doi.
org/ 10. 1016/j. vacci ne. 2021. 04. 065
World Health Organization (2019) National immunization coverage
scorecards estimates for 2018. National Immunization Coverage
Scorecards Estimates for 2018 (who. int)
World Health Organization, Global Vaccine Action Plan (2020) Global
Vaccine Action Plan (who. int)
Yaşlioğlu MM (2017) Sosyal bilimlerde faktör analizi ve geçerlilik:
Keşfedici ve doğrulayıcı faktör analizlerinin kullanılması. İstanbul
Üniversitesi İşletme Fakültesi Dergisi 46:74–85 369427 (dergi
park. org. tr)
Yıldızeli F, Alabaz D, Gözüyeşil E (2021) Determining the relationship
of parents, knowledge and attitudes and health literacy about the
admission or refusal of childhood immunization. J Pediatr Infect
15(2):e88–e96. https:// doi. org/ 10. 5578/ ced. 20211 9816
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
Springer Nature or its licensor (e.g. a society or other partner) holds
exclusive rights to this article under a publishing agreement with the
author(s) or other rightsholder(s); author self-archiving of the accepted
manuscript version of this article is solely governed by the terms of
such publishing agreement and applicable law.