Vaccine 33 (2015) 3556–3561
Contents lists available at ScienceDirect
Vaccine journal homepage: www.elsevier.com/locate/vaccine
Prevalence and associated factors of seasonal influenza vaccination among 24- to 59-month-old children in Hong Kong Anise M.S. Wu a , Joseph T.F. Lau b,c,∗ , Yee Ling Ma b , Mason M.C. Lau b a
Department of Psychology, Faculty of Social Sciences, University of Macau, Macau, China Centre for Health Behaviours Research, The Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China c Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China b
a r t i c l e
i n f o
Article history: Received 20 February 2015 Received in revised form 14 May 2015 Accepted 19 May 2015 Available online 1 June 2015 Keywords: Influenza Vaccination Health Belief Model Subjective norm Children Chinese
a b s t r a c t Background: Influenza results in severe complications among 24- to 59-month-old children, who are recommended by the WHO to take up influenza vaccination (IV) annually. Health promotion is warranted. Yet, there is a dearth of studies on IV prevalence and associated factors in this age group. Methods: A random population-based telephone survey interviewed 540 parents of Chinese children aged 24–59 months in Hong Kong during March through June, 2011. Constructs of the Health Belief Model (HBM) and subjective norm formed basis for assessing parental perceptions on influenza and IV. For data analysis, adjusted, and stepwise multiple logistic regression models were fit. Results: The prevalence of having taken up at least one dose and two doses of IV among children aged 24–59 months was 58.9 and 42.4%, respectively. Significant associated factors included family members’ IV experience (ORu = 5.37, 95% CI: 3.48, 8.29), variables related to the HBM constructs (except perceived severity) [perceived susceptibility of seasonal influenza (ORu = 2.03, 95% CI: 1.39, 2.95), perceived benefits of IV (ORu = 3.11, 95% CI: 2.05, 4.71), perceived barriers (ORu = 0.49, 95% CI: 0.25, 0.96) of IV, and cue to action (ORu = 4.79, 95% CI: 2.87, 7.99)], supportive subjective norm (ORu = 4.26, 95% CI: 2.91, 6.25), and level of fear felt during the H1N1 pandemic (ORu = 1.97, 95% CI: 1.01, 3.87). Adjusted for the child’s age, the same significant factors were found. Exposure to related media messages was statistically non-significant. Conclusion: The reported IV prevalence was higher than that of 24- to 59-month-old children reported in other studies. There is room for improvement through health promotion, which should modify parental cognitions related to HBM (except perceived severity and self-efficacy) and involve family members to create subjective norm. Media campaigns may be inadequate for promotion of IV; use of the setting approach may be considered. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Influenza results in serious complications and mortality among young children; [1,2] risk of influenza-related hospitalization among young children is comparable to that of older people and adults having high-risk medical conditions [3,4]. Influenza vaccination (IV) is effective among young children. The World Health Organization recommends children aged 6–59 months to take up IV annually [5]; a similar recommendation was given by the Hong Kong government (since the 2008/09 flu season) to children aged
∗ Corresponding author at: Centre for Health Behaviours Research, The Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China. Tel.: +852 2637 6606; fax: +852 2645 3098. E-mail address: [email protected] (J.T.F. Lau). http://dx.doi.org/10.1016/j.vaccine.2015.05.039 0264-410X/© 2015 Elsevier Ltd. All rights reserved.
6 months to less than 6 years [6]. With information of the vaccinated child registered, parents in Hong Kong pay a vaccination fee at a price with a discount of HKD80 (∼USD10) in 2011; the private practitioners involved then reimburse that amount from the government. The subsidy was doubled to HKD160 since 2014; the market price was about HKD200 in 2011. The Advisory Committee for Immunization Practices recommended children of 6–23 months old and 24–59 months old to take up IV in 2004 and 2006, respectively [7]. Parental perceptions concerning IV (e.g., perceived severity and perceived side effects), and hence prevalence and factors of IV concerning children below or above 2 years old may differ. A number of studies reported IV prevalence in children aged 6–23 (range = 41–74.4%) and 24–59 months old (range = 36–53.3%); the direction of the difference between such two groups varied from country to country [8–12]. We have conducted a study on children aged 6–23 months
A.M.S. Wu et al. / Vaccine 33 (2015) 3556–3561
in Hong Kong, reporting low prevalence of IV (9.0%) and associated factors of parental perceptions included recommendations received from health professionals and concerns of IV-induced side-effects [13]. This study focused on the age group of 24–59 months. The Health Belief Model (HBM) [14,15] is the most commonly used behavioral theory in IV research [16–23]. Its constructs, including perceived severity and susceptibility of influenza, perceived benefit and barrier of IV, cue to action (e.g., recommendation given by health professionals), and perceived self-efficacy in taking up IV, are significant factors of IV [16–23]; these studies targeted older people [22], health care workers [17], pregnant women [18,21], and those with chronic diseases [19]. However, no study has applied it to understand IV among 24- to 59-month-old children. Furthermore, HBM considers individual-level perceptions but not inter-personal factors. However, decisions affecting young children’s health are largely made by parents and often influenced by other family members’ views. Subjective norm, which is defined as significant others’ support for performing a health-related behavior, is highly relevant. It is a construct of the Theory of Planned Behaviors (TPB) [24]. Fear induced from previous outbreaks of emerging infectious diseases (e.g., SARS and H1N1) was associated with preventive behaviors including intention to take up IV [25–27]. The H1N1 pandemic occurred between 2009 and 2010. Since H1N1 makes up a high proportion of influenza during the post-pandemic period, we used fear experienced during that pandemic as a potential factor of IV. Other associated factors of children’s IV were used in this study, including family members’ IV experience [9,28,29] and exposure to influenza-related media messages [9,30]. We investigated prevalence and associated factors of IV status among Chinese children aged 24–59 months in Hong Kong. These factors included: (1) socio-demographic information and family members’ IV status, (2) parental perceptions based on the HBM and subjective norm of the TPB, (3) parental level of fear experienced during the H1N1 pandemic, and (4) parental exposure to related media messages. 2. Methods
3557
child had ever received IV), and detail of IV experience among vaccinated children. 2.2.2. Cognitive factors based on the HBM and subjective norm Questions on the six HBM constructs included two items on perceived child’s susceptibility for contracting influenza (next 12 months), two items on perceived severity of influenza onto the child, five items on perceived benefit (e.g., flu prevention), and six items on perceived barriers for taking up IV (e.g., side-effect), four items on related cue to action (e.g., advices obtained from friends and health care providers), and two items on perceived self-efficacy for having the child vaccinated. Two questions were related to subjective norm for having the child vaccinated (i.e., support from spouse and family members). References were made to other IV studies [13,20–22,31] to construct the question items, with modifications and additions. Summative scales were constructed. Ratings of the items related to perceived susceptibility and perceived severity ranged from 0 to 10; other items used 4-point Likert scales. The items are shown in Table 2. 2.2.3. Level of fear and media exposure Fear level was assessed by the question “How fearful were you during the H1N1 pandemic?” (“not at all”, “somewhat”, “quite”, “very much”, and “don’t know”). Frequency of exposure to media messages about IV promotion and influenza-related severe complications/deaths among children in the past 3 months (5-point Likert scale) were assessed. 2.3. Data analysis Univariate odds ratios (ORu) and respective 95% confidence intervals (CI) were firstly reported. Adjusted for background variables that were found to be significant in the univariate analysis; adjusted odds ratios (AOR) and respective 95% CI were estimated by fitting multiple logistic regression models. Considering significant variables of the adjusted analysis as candidates, backward stepwise logistic regression models were fit. SPSS 16.0 for Windows was used for data analyses. Statistical significance was taken at the 0.05 level.
2.1. Study design 3. Results A cross-sectional study was conducted during March through June, 2011. Random telephone numbers were selected from up-todate local telephone directories. The 24- to 59-month-old Chinese child whose last birthday was closest to the date of the interview was selected as the index child, and his/her parent (preference given to the mother) was invited to participate in the study. For unanswered calls, ≥3 extra calls were made before considering them as invalid numbers. Participants’ verbal informed consent was obtained before the interview commenced. Ethics approval was granted from the institute of the corresponding author. There were 787 households with an eligible child identified; 540 (540/787 = 68.6%) had a parent completed the interview.
3.1. Background characteristics Among the index children, 31.1, 24.9, and 44.3% were 24–35, 36–47, and 48–59 months old, respectively. About half were male. Majority were born in Hong Kong (99.1%), with both parents being Hong Kong residents (95.7%), being first (47.4%) or second (46.5%) in parity. Majority of participants were mothers (70%), with senior high or above education (91.3%); 55.0% were 35–44 years old; 55.4% employed full-time; 4.6% covered by CSSA. Other information is presented in Table 1. About 1/3 (33.9%) had had family member(s) having taken up IV in the last year.
2.2. Measures
3.2. Child’s IV experience
The questionnaire was constructed by a panel, considering results of a pilot study (n = 30). Test-retest reliability (2–week apart), assessed by the average Kappa of the items, was 0.67.
Of all children, 58.9% had ever taken up IV (42.4% had had ≥ 2 dozes). Of the ever-vaccinated children (n = 318), majority involved governmental subsidy (73%), and private clinics (74.8%). Among those children with related side effects (n = 50; 15.7%) reported, majority involved fever (73.2%) while
Contents lists available at ScienceDirect
Vaccine journal homepage: www.elsevier.com/locate/vaccine
Prevalence and associated factors of seasonal influenza vaccination among 24- to 59-month-old children in Hong Kong Anise M.S. Wu a , Joseph T.F. Lau b,c,∗ , Yee Ling Ma b , Mason M.C. Lau b a
Department of Psychology, Faculty of Social Sciences, University of Macau, Macau, China Centre for Health Behaviours Research, The Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China c Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China b
a r t i c l e
i n f o
Article history: Received 20 February 2015 Received in revised form 14 May 2015 Accepted 19 May 2015 Available online 1 June 2015 Keywords: Influenza Vaccination Health Belief Model Subjective norm Children Chinese
a b s t r a c t Background: Influenza results in severe complications among 24- to 59-month-old children, who are recommended by the WHO to take up influenza vaccination (IV) annually. Health promotion is warranted. Yet, there is a dearth of studies on IV prevalence and associated factors in this age group. Methods: A random population-based telephone survey interviewed 540 parents of Chinese children aged 24–59 months in Hong Kong during March through June, 2011. Constructs of the Health Belief Model (HBM) and subjective norm formed basis for assessing parental perceptions on influenza and IV. For data analysis, adjusted, and stepwise multiple logistic regression models were fit. Results: The prevalence of having taken up at least one dose and two doses of IV among children aged 24–59 months was 58.9 and 42.4%, respectively. Significant associated factors included family members’ IV experience (ORu = 5.37, 95% CI: 3.48, 8.29), variables related to the HBM constructs (except perceived severity) [perceived susceptibility of seasonal influenza (ORu = 2.03, 95% CI: 1.39, 2.95), perceived benefits of IV (ORu = 3.11, 95% CI: 2.05, 4.71), perceived barriers (ORu = 0.49, 95% CI: 0.25, 0.96) of IV, and cue to action (ORu = 4.79, 95% CI: 2.87, 7.99)], supportive subjective norm (ORu = 4.26, 95% CI: 2.91, 6.25), and level of fear felt during the H1N1 pandemic (ORu = 1.97, 95% CI: 1.01, 3.87). Adjusted for the child’s age, the same significant factors were found. Exposure to related media messages was statistically non-significant. Conclusion: The reported IV prevalence was higher than that of 24- to 59-month-old children reported in other studies. There is room for improvement through health promotion, which should modify parental cognitions related to HBM (except perceived severity and self-efficacy) and involve family members to create subjective norm. Media campaigns may be inadequate for promotion of IV; use of the setting approach may be considered. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Influenza results in serious complications and mortality among young children; [1,2] risk of influenza-related hospitalization among young children is comparable to that of older people and adults having high-risk medical conditions [3,4]. Influenza vaccination (IV) is effective among young children. The World Health Organization recommends children aged 6–59 months to take up IV annually [5]; a similar recommendation was given by the Hong Kong government (since the 2008/09 flu season) to children aged
∗ Corresponding author at: Centre for Health Behaviours Research, The Jockey Club School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China. Tel.: +852 2637 6606; fax: +852 2645 3098. E-mail address: [email protected] (J.T.F. Lau). http://dx.doi.org/10.1016/j.vaccine.2015.05.039 0264-410X/© 2015 Elsevier Ltd. All rights reserved.
6 months to less than 6 years [6]. With information of the vaccinated child registered, parents in Hong Kong pay a vaccination fee at a price with a discount of HKD80 (∼USD10) in 2011; the private practitioners involved then reimburse that amount from the government. The subsidy was doubled to HKD160 since 2014; the market price was about HKD200 in 2011. The Advisory Committee for Immunization Practices recommended children of 6–23 months old and 24–59 months old to take up IV in 2004 and 2006, respectively [7]. Parental perceptions concerning IV (e.g., perceived severity and perceived side effects), and hence prevalence and factors of IV concerning children below or above 2 years old may differ. A number of studies reported IV prevalence in children aged 6–23 (range = 41–74.4%) and 24–59 months old (range = 36–53.3%); the direction of the difference between such two groups varied from country to country [8–12]. We have conducted a study on children aged 6–23 months
A.M.S. Wu et al. / Vaccine 33 (2015) 3556–3561
in Hong Kong, reporting low prevalence of IV (9.0%) and associated factors of parental perceptions included recommendations received from health professionals and concerns of IV-induced side-effects [13]. This study focused on the age group of 24–59 months. The Health Belief Model (HBM) [14,15] is the most commonly used behavioral theory in IV research [16–23]. Its constructs, including perceived severity and susceptibility of influenza, perceived benefit and barrier of IV, cue to action (e.g., recommendation given by health professionals), and perceived self-efficacy in taking up IV, are significant factors of IV [16–23]; these studies targeted older people [22], health care workers [17], pregnant women [18,21], and those with chronic diseases [19]. However, no study has applied it to understand IV among 24- to 59-month-old children. Furthermore, HBM considers individual-level perceptions but not inter-personal factors. However, decisions affecting young children’s health are largely made by parents and often influenced by other family members’ views. Subjective norm, which is defined as significant others’ support for performing a health-related behavior, is highly relevant. It is a construct of the Theory of Planned Behaviors (TPB) [24]. Fear induced from previous outbreaks of emerging infectious diseases (e.g., SARS and H1N1) was associated with preventive behaviors including intention to take up IV [25–27]. The H1N1 pandemic occurred between 2009 and 2010. Since H1N1 makes up a high proportion of influenza during the post-pandemic period, we used fear experienced during that pandemic as a potential factor of IV. Other associated factors of children’s IV were used in this study, including family members’ IV experience [9,28,29] and exposure to influenza-related media messages [9,30]. We investigated prevalence and associated factors of IV status among Chinese children aged 24–59 months in Hong Kong. These factors included: (1) socio-demographic information and family members’ IV status, (2) parental perceptions based on the HBM and subjective norm of the TPB, (3) parental level of fear experienced during the H1N1 pandemic, and (4) parental exposure to related media messages. 2. Methods
3557
child had ever received IV), and detail of IV experience among vaccinated children. 2.2.2. Cognitive factors based on the HBM and subjective norm Questions on the six HBM constructs included two items on perceived child’s susceptibility for contracting influenza (next 12 months), two items on perceived severity of influenza onto the child, five items on perceived benefit (e.g., flu prevention), and six items on perceived barriers for taking up IV (e.g., side-effect), four items on related cue to action (e.g., advices obtained from friends and health care providers), and two items on perceived self-efficacy for having the child vaccinated. Two questions were related to subjective norm for having the child vaccinated (i.e., support from spouse and family members). References were made to other IV studies [13,20–22,31] to construct the question items, with modifications and additions. Summative scales were constructed. Ratings of the items related to perceived susceptibility and perceived severity ranged from 0 to 10; other items used 4-point Likert scales. The items are shown in Table 2. 2.2.3. Level of fear and media exposure Fear level was assessed by the question “How fearful were you during the H1N1 pandemic?” (“not at all”, “somewhat”, “quite”, “very much”, and “don’t know”). Frequency of exposure to media messages about IV promotion and influenza-related severe complications/deaths among children in the past 3 months (5-point Likert scale) were assessed. 2.3. Data analysis Univariate odds ratios (ORu) and respective 95% confidence intervals (CI) were firstly reported. Adjusted for background variables that were found to be significant in the univariate analysis; adjusted odds ratios (AOR) and respective 95% CI were estimated by fitting multiple logistic regression models. Considering significant variables of the adjusted analysis as candidates, backward stepwise logistic regression models were fit. SPSS 16.0 for Windows was used for data analyses. Statistical significance was taken at the 0.05 level.
2.1. Study design 3. Results A cross-sectional study was conducted during March through June, 2011. Random telephone numbers were selected from up-todate local telephone directories. The 24- to 59-month-old Chinese child whose last birthday was closest to the date of the interview was selected as the index child, and his/her parent (preference given to the mother) was invited to participate in the study. For unanswered calls, ≥3 extra calls were made before considering them as invalid numbers. Participants’ verbal informed consent was obtained before the interview commenced. Ethics approval was granted from the institute of the corresponding author. There were 787 households with an eligible child identified; 540 (540/787 = 68.6%) had a parent completed the interview.
3.1. Background characteristics Among the index children, 31.1, 24.9, and 44.3% were 24–35, 36–47, and 48–59 months old, respectively. About half were male. Majority were born in Hong Kong (99.1%), with both parents being Hong Kong residents (95.7%), being first (47.4%) or second (46.5%) in parity. Majority of participants were mothers (70%), with senior high or above education (91.3%); 55.0% were 35–44 years old; 55.4% employed full-time; 4.6% covered by CSSA. Other information is presented in Table 1. About 1/3 (33.9%) had had family member(s) having taken up IV in the last year.
2.2. Measures
3.2. Child’s IV experience
The questionnaire was constructed by a panel, considering results of a pilot study (n = 30). Test-retest reliability (2–week apart), assessed by the average Kappa of the items, was 0.67.
Of all children, 58.9% had ever taken up IV (42.4% had had ≥ 2 dozes). Of the ever-vaccinated children (n = 318), majority involved governmental subsidy (73%), and private clinics (74.8%). Among those children with related side effects (n = 50; 15.7%) reported, majority involved fever (73.2%) while
