Vaccinations among Italian adolescents: Knowledge, attitude and behavior

ABSTRACT

This study evaluates knowledge, attitudes and behaviors of adolescents regarding vaccinations. A cross-sectional study was conducted among a sample of 771 adolescents, aged 11 to 18 selected from a random sample of 5 public schools, in the period between March and May 2017, in the geographical area of Naples. A self-administered questionnaire was used to seek information about: 1) socio-demographic characteristics; 2) knowledge of vaccine-preventable diseases; 3) attitudes towards vaccinations; 4) behavior regarding vaccinations. 57.2% had a fair/satisfactory knowledge of vaccine-preventable diseases. This knowledge was significantly higher in those who had at least one graduated parent, those who had received information about the vaccines from physicians and those who needed additional information about the vaccines. With regards to attitude, 41.3% of adolescents had a very favorable attitude by responding 9 or 10 towards the utility of vaccines in preventing diseases. This was significantly associated with the usefulness of information received about vaccinations and with age of respondents. Regarding vaccination decisions, 47.2% believed that adolescents should make vaccination decisions for themselves. These results highlight the need to implement educational interventions to improve adolescents' understanding of vaccinations so that they are more informed in decisions regarding their health.

KEYWORDS:

• adolescent
• attitude
• behavior
• knowledge
• vaccination
• vaccination decisions
• Italy

Introduction

Vaccination is, as is well known, one of the greatest strategies for primary prevention of infectious diseases, representing a real goal for public health. Since their introduction, vaccines have reduced morbidity, mortality, and the social and economic burden that are associated with a number of common childhood diseases.¹

Despite all these benefits, vaccinations are often perceived as unsafe and unnecessary in the population.² Moreover, the practice of vaccinations, widely shared and implemented in the pediatric field, is not yet sufficiently widespread in other age groups, such as adolescents. A recent recommendation of the American Academy of Pediatrics, dedicates a lot of space to emphasize the usefulness and importance of vaccinations in this age group. Indeed, adolescence is the time to administer the booster doses of vaccinations carried out in newborns (tetanus and pertussis vaccines and Poliomyelitis vaccine) and other vaccinations that are administered at this age; the papillomavirus vaccine and the meningococcal vaccines.³

The immunization coverage data in childhood for 2016, published by the Ministry of Health, revealed that Italy is still far from achieving its vaccine coverage objective.⁴ Moreover, to address this alarming low level in vaccinations coverage, a law was passed in July 2017 reintroducing the obligation of vaccinations as a prerequisite for attending public schools.⁵ Therefore, particularly for adolescents (for the birth cohort in 2000) there is a coverage of just over 60% for diphtheria, polio and tetanus, while in Campania this percentage drops to about 45%.⁶

It is therefore interesting to assess the knowledge of adolescents in the field of vaccinations, as they, in addition to parents and providers, could be an important strength in this practice by making a conscious contribution to choices and decisions concerning their health. Adolescents are more likely to establish their vaccine-related attitudes independently from parents.⁷

The analysis of literature has highlighted several surveys assessing knowledge, attitudes and behaviors of parents^8-12 and physicians^8,13-14 about vaccinations, most of them have addressed only a specific disease preventable with vaccination,^15-18 while knowledge, attitudes and behaviors of adolescents were poorly described.^19-22 However, in Italy, to the best of our knowledge, little attention has also been given to the issue of adolescents' knowledge, attitudes, and behaviors towards vaccinations. Therefore, in this current investigation, conducted among a sample of adolescents in Italy, the primary objective was to document the level of knowledge, the attitudes, and the reported behaviors towards vaccinations and the second objective was to examine the extent to which determinants are associated with these outcomes.

Results

Adolescents' characteristics

Of the 776 questionnaires distributed, 5 were excluded due to inconsistent information. Therefore, a total of 771 questionnaires were considered with a response rate of 99.4%. The principal characteristics of the study group are shown in Table 1. The mean age of participants was 15.1 years, slightly more than half were females, almost all were of Italian nationality, 6.9% had at least one parent who was a health care professional.

Table 1. Socio-demographic and selected information about the study population.

	N	%
Age	15.07±2.19 (11–19)^*
11–13	216	28
14–16	334	43.3
17–19	221	28.7
Sex
Male	363	47.1
Female	408	52.9
Nationality
Italian	736	95.5
Other	35	4.5
School attended
Middle school	296	38.4
High school	475	61.6
Number of siblings
None	110	14.3
≥1	659	85.7
Father's education
No formal education	13	1.7
Elementary	22	3
Middle school	167	22.5
High school	286	38.5
College degree	255	34.3
Mother's education
No formal education	14	1.9
Elementary	25	3.3
Middle school	161	21.4
High school	282	37.4
College degree	271	36
Father's employment status
Unemployed	31	4.3
Employed	687	95.7
Mother's employment status
Unemployed	308	41.3
Employed	438	58.7
At least one chronic disease
Yes	174	22.6
No	597	77.4

* Mean±Standard deviation (Range).

Numbers for each item may not add up to total number of study population due to missing values.

Adolescents' knowledge

Table 2 shows a comparison of knowledge and socio-demographic characteristics of the study population. Almost all (95%) reported that they had heard of vaccines as interventions that protect us from serious infectious diseases. Regarding the knowledge of vaccine-preventable diseases, the values were, in descending order, meningitis (72.2%), measles (71.9%), varicella (68.2%), tetanus (63.8%), rubella (54.7%), influenza (47.4%), hepatitis B (38.4%), pertussis (26.9%), polio (25.7%), cervical cancer (21.7%), mumps (20.8%), pneumonia (20%) diphtheria (16.8%). Moreover, some diseases have been identified incorrectly as vaccine-preventable diseases such as: hepatitis C (35.3%), AIDS (16.9%), diabetes (6.7%) and heart attack (3.4%). Calculations and categorization of the knowledge score revealed that 42.8%, 23.5%, and 33.7% of the participants obtained poor, fair, and satisfactory knowledge scores respectively. Multiple logistic regression analysis showed that having at least one graduated parent (OR = 1.71; 95% CI 1.24–2.37), having received information about vaccinations from physicians (OR = 1.49; 95% CI 1.09–2.05) and declaring need of additional information about vaccinations (OR = 1.62; 95% CI 1.16–2.25) were significantly more likely to have fair/satisfactory knowledge about vaccine-preventable diseases. Moreover, the odds were lower in adolescents under 14 years of age (OR = 0.27; 95% CI 0.18–0.41) compared with the age group 17–19 (Model 1 in Table 3).

Table 2. Comparison of knowledge and socio-demographic characteristics of study population.

	Poor knowledge		Fair/satisfactory knowledge
	n = 338		n = 433
	N	%	N	%	Univariate p
Age
11–13	142	42	74	17.1
14–16	126	37.3	208	48
17–19	70	20.7	151	34.9	<0.001
Sex
Male	168	49.7	195	45	0.197
Female	170	50.3	238	55
Nationality
Not Italian	22	6.5	13	3	0.020
Italian	316	93.5	420	97
School attended
Primary school	176	52.1	120	27.7	<0.001
Secondary school	162	47.9	313	72.3
Number of siblings
None	52	15.5	58	13.4	0.414
≥1	284	84.5	375	36.6
At least one graduate parent
No	206	60.9	202	46.7	<0.001
Yes	132	39.1	231	53.3
At least one healthcare worker parent
No	324	95.9	394	91	0.008
Yes	14	4.1	39	9
At least one chronic disease
No	266	78.7	331	76.4	0.457
Yes	72	21.3	102	23.6

Table 3. Multivariate logistic analysis to characterize factors associated with the different outcomes of interest.

Variable	OR	SE	95% CI	p value
Model 1. Knowledge of vaccine-preventable diseases
Log likelihood = -454.74, χ^2 = 84 (7 df), p<0.0001 (sample size = 730)
Age 11–13	0.27	0.06	0.18–0.41	<0.001
Age 14–16	0.78	0.15	0.53–1.13	0.195
Age 17–19	1.0^*	—	—	—
Have at least one graduated parent	1.71	0.28	1.24–2.37	0.001
Need additional information about vaccination	1.61	0.27	1.16–2.25	0.004
Have received information about vaccinations from physicians	1.49	0.24	1.09–2.05	0.013
Have at least one chronic disease	1.27	0.25	0.87–1.86	0.216
Female	1.2	0.19	0.87–1.65	0.253
Have at least one parent who is a health care professional	1.45	0.50	0.74–2.86	0.276
Backward elimination
Utility of information received about vaccinations
Number of siblings
Model 2. Utility of vaccinations in order to prevent diseases
Log likelihood = -445.18, χ^2 = 95.84 (7 df), p<0.0001 (sample size = 729)
Age 11–13	2.35	0.52	1.53–3.63	<0.001
Age 14–16	1.23	0.24	0.84–1.81	0.288
Age 17–19	1.0^*	—	—	—
Utility of information received about vaccinations	3.97	0.75	2.74–5.76	<0.001
Don't have at least one chronic disease	0.72	0.14	0.47–1.06	0.096
Male	0.8	0.13	0.58–1.11	0.188
Have received information about vaccinations from physicians	1.23	0.20	0.90–1.70	0.196
Have at least one graduated parent	1.20	0.19	0.87–1.65	0.274
Backward elimination
Need additional information about vaccinations
Knowledge of vaccine-preventable diseases
Number of siblings
Have at least one parent who is a health care professional
Model 3. Adolescents should make vaccination decision for themselves
Log likelihood = -480.73, χ^2 = 47.65 (8 df), p<0.0001 (sample size = 729)
Age 11–13	0.3	0.07	0.19–0.47	<0.001
Age 14–16	0.42	0.08	0.29–0.6	<0.001
Age 17–19	1.0^*	—	—	—
Attitude towards the dangers of vaccinations	1.51	0.38	0.91–2.49	0.107
Utility of information received about vaccinations	1.3	0.25	0.89–1.89	0.172
Don't have received information about vaccinations from physicians	0.81	0.13	0.6–1.11	0.189
Negative attitude towards the utility of vaccinations	0.81	0.13	0.59–1.13	0.216
Don't have at least one graduated parent	0.85	0.13	0.63–1.16	0.311
Knowledge of vaccine-preventable diseases	1.17	0.19	0.84–1.61	0.351
Backward elimination
Have at least one parent who is a health care professional
Female
Number of siblings
Need additional information about vaccinations
Have at least one chronic disease
Have at least one vaccination in the last year
Talk with parents about vaccinations
Have at least one visit to the physician in the last year
Model 4. Utility of information received about vaccinations
Log likelihood = -349.17, χ^2 = 129.68 (13 df), p<0.0001 (sample size = 729)
Age 11–13	4.59	1.28	2.65–7.94	<0.001
Age 14–16	2.29	0.59	1.38–3.79	0.001
Age 17–19	1.0^*	—	—	—
Positive attitude towards the utility of vaccinations	4.11	0.8	2.8–6.02	<0.001
Have received information about vaccinations from physicians	1.54	0.29	1.05–2.24	0.026
Talk with parents about vaccinations	1.79	0.47	1.06–3.01	0.028
Don't have at least one graduated parent	0.68	0.14	0.46–1.01	0.057
Have at least one vaccinations in the last year	1.49	0.31	0.99–2.24	0.056
Need additional information about vaccinations	1.43	0.28	0.97–2.1	0.072
Male	0.71	0.14	0.48–1.05	0.085
Attitude towards the dangers of vaccinations	1.69	0.52	0.93–3.07	0.087
Autonomy in decision to vaccinate	1.27	0.24	0.87–1.85	0.215
Have at least one chronic disease	1.26	0.28	0.82–1.95	0.290
Don't have at least one parent who is a health care professional	0.77	0.28	0.29–1.52	0.337
Backward elimination
Knowledge of vaccine-preventable diseases
Number of siblings
Have at least one visit to the physician in the last year

* Reference category in multivariate analysis.

Adolescents' attitudes

The mean total values of adolescents' attitudes regarding the usefulness of vaccines to prevent diseases, measured on a ten-point Likert scale ranging scores from 1 to 10 with higher scores indicating higher utility, was 7.9 and 41.3% had a very favorable attitude by responding 9 or 10 towards the usefulness of vaccines to prevent diseases. After multivariate logistic adjustments, this model revealed that the usefulness of information received about vaccinations (OR = 3.97; 95% CI 2.74–5.76) and being adolescents under 14 years of age (OR = 2.35; 95% CI 1.52–3.63) compared to the age group 17–19 were significantly associated with the outcome (Model 2 in Table 3). Adolescents were asked about their beliefs towards the dangers of vaccinations and only 10.4% considered them very unsafe, with a mean total score of 4.3.

Adolescents' behaviors

Overall, 55.5% of participants reported to know what vaccinations they had received in infancy and 79% of adolescents spoke with parents about vaccinations. Regarding vaccination decisions, just about half (47.2%) believed that adolescents should make vaccination decisions for themselves. The significant predictors of the belief that adolescents should make vaccination decisions for themselves were lower in adolescents under 14 years of age (OR = 0.3; 95% CI 0.19–0.47) and with the age group 14–16 (OR = 0.42; 95% CI 0.29–0.6) compared to the age group 17–19 (Model 3 in Table 3). When we asked to indicate what infectious diseases had been contracted in their life the participants indicated: influenza (82.1%), varicella (67.6%), measles (17.4%), rubella (5.8%), pertussis (2.2%), mumps (1%), hepatitis A (0.4%), meningitis (0.1%). 33.3% of adolescents reported having at least one vaccination in the last year and 81.7% had reported at least one visit to the physician in the last year.

Adolescents' major sources of knowledge

Questions concerning sources of information for the study population indicated that the majority acquired their vaccinations knowledge from physicians (43.6%); other sources in order were newspapers/broadcast (70%), parents (62.9%), internet (30.4%), and school (24.4%). The mean total values of adolescents' attitudes regarding the utility of sources of knowledge, measured on a ten-point Likert scale ranging from 1 scores to 10 with higher indicating high utility, was 6.9 and 25.4% had a very favorable attitude by responding 9 or 10 towards the utility of sources of knowledge. Multivariate logistic regression analysis showed that this positive attitude was observed in those who had spoken with parents about vaccinations (OR = 1.79; 95% CI 1.06–3.01), those who believed that vaccinations were useful to prevent diseases (OR = 4.11; 95% CI 2.8–6.02) and those who had acquired information from physicians (OR = 1.54; 95% CI 1.05–2.24). Moreover, adolescents in the age group 11–13 (OR = 4.59; 95% CI 2.65–7.94) and in the age group 14–16 (OR = 2.29; 95% CI 1.38–3.79) believed the information received about vaccinations was more useful than adolescents in the age group 17–19. (Model 4 in Table 3). 35.5% of participants wanted more information about vaccinations.

Discussion

Vaccinations are the most effective interventions for the primary prevention of infectious diseases and an essential element for public health, especially for childhood and adolescence. While immunization coverage rate for children depends exclusively on parental decisions, this differs among adolescents that could decide independently from their parents. Therefore, assessing awareness and knowledge of vaccination among adolescents, as a target group for immunization programs, is crucial. As far as we know, the present study is one of the few investigations designed to collect detailed data on the knowledge, attitudes and behaviors towards vaccinations among a sample of adolescents. Comparison with other studies is very difficult due to the different methodologies and available samples. Our results indicate that adolescents' knowledge about vaccine-preventable diseases was limited, indeed only 33.7% of participants obtained a satisfactory knowledge score. Particularly striking was that a very high proportion did not know that hepatitis B, pertussis, polio, cervical cancer, mumps, pneumonia and diphtheria was vaccine-preventable diseases. Furthermore, it was also quite noteworthy that there were some misconceptions. Indeed, some participants thought that hepatitis C, AIDS, diabetes and heart attacks were vaccine-preventable diseases. This finding was lower than those observed in a survey of Belgian and immigrant adolescents.²³ In other studies that evaluated knowledge for a single vaccine-preventable disease only, respectively 54.9% males aged 14–24 years,¹⁷ 42.1% of women aged 14–24 years²⁴ and 32.4% of young girls and boys²⁵ knew that vaccination was a preventive measure for HPV infections and cervical cancer. Another interesting finding was that the mean value of the perceived usefulness of vaccines to prevent diseases was 7.9 and 41.3% reported high concern. Our result of the perceived usefulness of vaccines to prevent diseases is lower than the 71% and 64.1% found in two studies conducted in USA²⁶ and in Australia.²⁷ Therefore, our results study provide evidence that only 10.4% of adolescents believe vaccinations to be unsafe. This percentage is lower than that found in a study already cited conducted in the USA. Indeed, 31% of the adolescents in this study perceived vaccines to be “less safe”.²⁶ As in these prior studies, our results suggest that continued efforts are urgently needed to educate adolescents about vaccinations: to improve awareness of their usefulness, safety and consequently increase vaccination coverage rates. In this study, 47.2% of the participants declared that adolescents should make vaccination decisions for themselves. This percentage is lower than a previous study conducted in the USA where 69% of adolescents declare to be “somewhat comfortable” or “very comfortable” to make vaccine decisions for themselves;²⁶ but it is much higher than the study of Wang et al.²⁷ where only 3.8% of adolescent participants believed that adolescents should make the decision themselves. The potential role of adolescents in the decision-making should not be neglected. Involving adolescents in decision-making could lead to higher compliance regarding issues concerning their health.^7,28-30 In this study, 62.9% of adolescents reported parents as one of their sources of information about vaccinations. This percentage is lower than another study, where 80% of teenagers indicated parents as the main source of information about vaccinations.²⁶ Moreover, in our study, 43.6% of adolescents reported physicians as another important source of information. This finding is similar (53.6%) to that highlighted in the study of Wang et al.,²⁷ while a higher percentage (81%) is reported in the study conducted by Devroey et al.²³ Our results showed that having received information about the vaccines from physicians was significantly associated, at multivariate regression analysis, with knowledge about vaccine-preventable diseases. This association has also been found in another study that investigated the factors associated with the male adolescent's knowledge of vaccination, although with a different aim.¹⁷ In our study, the multivariate regression analysis showed that the utility of information received about vaccination was significantly associated with a positive attitude regarding the usefulness of vaccines to prevent diseases. This result highlights the importance of quality of information, based on the best available scientific evidence, on communication strategies and on the training of healthcare professionals since both scientific knowledge and communication skills are crucial to achieving the goal of vaccination.

This study has some potential limitations. Firstly, in cross-sectional studies it is difficult to precisely determine temporal sequence between the dependent and independent variables. Secondly, there was a possibility of bias due to participants with favorable attitudes towards vaccination potentially being more likely to respond to the questionnaire. Thirdly, in this survey, based on a self-administrated questionnaire, participants could report correct behavior and not that which they deemed incorrect. Finally, the data is self-reported and thus subject to response bias particularly when dealing with questions regarding vaccinations and infectious disease contracted in their life. Despite these limitations, the major strength of the study is the high response rate that makes results representative enough of the population. In conclusion, the study results provide important insights into the knowledge, positive attitudes, and behavior of adolescents towards vaccinations. In particular, our study highlights a low level of knowledge about vaccine-preventable diseases but positive attitudes towards vaccinations. Moreover, adolescents believe that they should make vaccination decisions for themselves. The crucial point to increasing immunization rates and decreasing vaccine-preventable diseases among adolescents is to focus on educating adolescents in Italy. Therefore, there is an urgent need for educational intervention to improve the level of knowledge about vaccines. Furthermore, future studies should be focused on implementing educational interventions for adolescents and evaluating their effectiveness.

Materials and methods

The data for this cross-sectional investigation was collected in the period between March and May 2017 from 771 adolescents aged 11 to 18 selected from a random sample of 5 public schools in the geographic area of the Campania region, in the South of Italy. The sample was selected with a two-stage cluster method. Five public middle and high schools were randomly chosen. A simple random technique was adopted in selecting students from each school.

Before the study initiation, a meeting with the director of each randomly selected school was held to present the project and their approval and cooperation were obtained. Furthermore, parents were asked for written permission for their children to participate in the study. The cover letter was addressed to the parents to indicate the purpose of the survey, highlight why their children were selected, also indicating that participation in the survey was voluntary and that privacy and confidentiality would be strictly protected as no personal identifiers were included in the questionnaire and data would be presented only in an aggregated manner. These policies were also printed explicitly on the front page of the questionnaire. The number of students to be randomly sampled in this study was determined based on the assumptions that 50% of the adolescents have heard about vaccinations, using a confidence interval of 95%, a margin of error of 5%, and an expected response rate of 95%. It was estimated that a total number of 750 adolescents for the study would need to be enrolled.

The survey instrument, built ad hoc for the present survey, was an anonymous, structured questionnaire. A researcher in each classroom gave oral instructions about filling in the questionnaire to the students who had secured parental consent.

The questionnaire collected information on the following items: (1) student socio-demographics and health history, including age, gender, nationality, number of cohabiting family members, number of siblings, parents' educational level, parents' working activity, number and type of chronic diseases; (2) knowledge about vaccines (definition of vaccines and vaccine-preventable diseases); (3) attitudes pertaining to assess opinions about the perceived benefits and risks of vaccinations; (4) practices related to the vaccines, vaccination decision-making for themselves; (5) sources of information about vaccines, usefulness of the information received and need of information regarding vaccines.

A pilot study was carried out with a sample of 50 students (and their responses were included in the final sample number of the survey). Approval of this survey was obtained by the Ethics Committee of the University of Campania “Luigi Vanvitelli” after examining the study protocol and the questionnaire.

Statistical analysis

A scoring system was done for determining the level of knowledge about vaccine-preventable diseases. The diseases considered were 17 and, for each disease, a score of “1” was put for the correct answer and “0” for the incorrect or unknown answers. The total knowledge score was calculated and it ranged from 0 to 17. This knowledge score was then categorized into: poor knowledge for answering less than half of the questions (<50% of total score), fair knowledge (50–76.9% of total score), and satisfactory knowledge (>76.9% of total score). Following a descriptive analysis of the data, the inferential analysis was conducted according to a double stage strategy. In the first stage, four multivariate logistic regression full models were built to evaluate the effect of each independent variable on the following outcomes of interest: knowledge about vaccine-preventable diseases (poor = 0; fair/satisfactory = 1) (Model 1), positive attitude towards the usefulness of vaccinations (<9 = 0; 9–10 = 1) (Model 2), belief that they should make the decision about vaccinations for themselves (no = 0; yes = 1) (Model 3) and utility of information received about vaccines (<9 = 0; 9–10 = 1) (Model 4). In this stage, the selection of variables included in saturated models was done considering previous investigation in the literature, while other variables were chosen because we were considered as interesting predictors of the outcomes. In the second stage, the variables included in the final models were determined using backwards selection procedure and the significance level for variables for removal from the model was set at 0.4. The Hosmer and Lemeshow test was used to assess the goodness-of-fit of the models.³¹ The following independent variables that were considered potentially associated with the outcomes were included in all models: age (three categories: 11–13 years; 14–16 years; 17–19 years), gender (male = 0; female = 1), educational level of at least one parent (others = 0; college degree or higher = 1), number of siblings (none = 0; 1 = ≥1), number of cohabiting family members (continuous), at least one parent who was a health care professional (no = 0; yes = 1), at least one chronic disease (0 = none; 1 = ≥1), physicians as a source of information about vaccinations (no = 0; yes = 1), need of additional information about vaccinations (no = 0; yes = 1). The variable utility of information received about vaccinations (no = 0; yes = 1) was included in Model 1, in Model 2 and in Model 3. The variable knowledge about vaccine-preventable diseases (poor = 0; fair/satisfactory = 1) was included in Model 2, in Model 3 and in Model 4. The variables positive attitude towards the usefulness of vaccinations (<9 = 0; 9–10 = 1), attitude towards the dangers of vaccinations (1–7 = 0; 8–10 = 1), discussing vaccinations with parents (no = 0; yes = 1), at least one vaccination in the last year (no = 0; yes = 1), at least one visit to a physician in the last year (no = 0; yes = 1) were included in Model 3 and Model 4. Finally, the variable belief they should make the decision about vaccinations for themselves (no = 0; yes = 1) was included in Model 4.

The results of the multivariate regression models have been expressed as odds ratios (ORs) and 95% confidence intervals (CIs) with a statistically significant level of p-value ≤0.05. Statistical analyses were performed using Stata version 10.1 software.³²

Disclosure of potential conflicts of interest

The authors report no conflict of interest.

Acknowledgments

The authors would like to offer their sincere thanks to all adolescents who participated in this study. The study would not have been possible without the co-operation of the Schools, and we are indebted to them for their contributions. Preliminary results were presented at the 50° National Congress of the Italian Public Health Association. November 22-25, Torino, Italy.