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Prevalence and determinants of influenza vaccination in the Hong Kong Chinese adult population
American Journal of Infection Control 40 (2012) e225-7
Contents lists available at ScienceDirect
American Journal of Infection Control
American Journal of Infection Control
journal homepage: www.ajicjournal.org
Major article
Prevalence and determinants of influenza vaccination in the Hong Kong Chinese adult population Joseph T.F. Lau PhD a, b, *, Doreen W.H. Au PhD a, H.Y. Tsui PhD a, K.C. Choi PhD a a b
Centre for Health Behaviours Research, School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China Centre for Medical Anthropology and Behavioral Health, Sun Yat-sen University, Guangzhou, China
Key Words: Respiratory diseases Vaccine Coverage Perception Health Belief Model China
Background: The study examined the prevalence and associated factors of influenza vaccination (IV) among the general adult population in Hong Kong. Methods: A population-based, random telephone survey interviewed 1,102 Hong Kong Chinese adults aged 18-64 years old in 2006. Results: Of all study participants, 95.5% had heard of IV, and only 28.1% had ever received IV. Associated factors included knowledge that IV is required annually, variables related to the Health Belief Model (HBM) (eg, perceived adverse effects, perceived efficacy), and advices given by health care professionals. Conclusions: The prevalence of IV was moderately low and factors related to the HBM were found predictive of IV. Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.
Influenza causes substantial morbidity and mortality to adults of 18 to 64 years old.1 Influenza vaccination (IV) is associated with shorter duration of stay in hospital,2 lower prevalence of respiratory illnesses, and lower absenteeism from work.3 Factors derived from the Health Belief Model (HBM) such as perceived barriers, perceived benefits, and perceived severity; socioeconomic factors; health professionals’ advice; knowledge; and attitudes are significantly associated with IV.4,5 Few of these studies were conducted in Asia. METHODS An anonymous, population-based, random telephone survey was conducted during April and May 2006. Those self-reported having been diagnosed as having chronic diseases were excluded from the study. We contacted 1,594 eligible Chinese adults (18-64 years old), of whom 1,102 were interviewed. The same telephone survey method has been used in many local studies (for example, * Address correspondence to Joseph T. F. Lau, PhD, Professor, Associate Director, School of Public Health and Primary Care, Director, Centre for Health Behaviours Research, School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, 5/F, School of Public Health, Prince of Wales Hospital, Shatin, NT, Hong Kong, China. E-mail address: [email protected] (J.T.F. Lau). Supported by Department of Health, Hong Kong Special Administrative Region. Conflicts of interest: None to report.
Table 1 Sociodemographic characteristics of all participants N* Sex Male 526 Female 576 Education level Primary school or below 137 Junior/senior secondary school 553 Postsecondary or matriculation 89 University or above 319 Marital status Single 358 Married/cohabiting 727 Divorced/separated/widowed 11 Having chronic diseases Yes 91 No 1,011 Being health care professional Yes 42 No 1,060 Have chances of contacting live poultry at work Yes 21 No 1,081 Receiving comprehensive Social Security assistance (CSSA) Yes 12 No 1,077 Refused to answer 13
% 47.7 52.3 12.5 50.4 8.1 29.1 32.7 66.3 1.0 8.3 91.7 3.8 96.2 1.9 98.1 1.1 97.7 1.2
*Valid percentages were reported (ie, missing values were not included in the denominator), and the frequencies therefore may not sum up to the total.
0196-6553/$36.00 - Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.ajic.2012.01.036
e226
J.T.F. Lau et al. / American Journal of Infection Control 40 (2012) e225-7
Table 2 Factors associated with influenza vaccination behavior and intention among adults who had heard of IV: N ¼ 1,052 Model I Had ever received IV n* Age group, yr 18-29 30-39 40-49 50 Education level Primary school or below Junior/senior secondary school Postsecondary or matriculation University or above Being health care professional No Yes Recommendation from health care professionals to uptake IV No Yes Knowledge that IV could reduce the risk of influenza-induced complications (eg, pneumonia) or hospitalization or death No/uncertain Yes Knowledge that IV is required every year No Yes Do not know Perceived adverse effects of IV No adverse effect Not severe Severe Do not know Perceived efficacy of IV for preventing flu Not efficacious Efficacious Do not know Perceived health impact on oneself if contracting influenza No effect/mild Moderate Severe/very severe Do not know
Model II Inclined to receive IV in the next year
%
ORu
ORm
%
242 251 303 256
23.6 35.5 30.0 28.5
1.00 1.78y 1.39 1.29
1.00 1.91 (1.17-3.09)y 1.96 (1.20-3.18)y 1.83 (1.08-3.10)z
UN
122 531 86 310
25.4 25.4 20.9 40.3
1.00 1.00 0.78 1.98y
1.00 0.98 (0.56-1.74) 0.93 (0.41-2.10) 2.25 (1.22-4.17)y
UN
1,010 42
27.8 69.0
1.00 5.79y
1.00 2.46 (1.10-5.50)y
903 149
22.8 69.8
1.00 7.82y
1.00 5.96 (3.82-9.30)y
287 765
UN
343 492 217
23.6 38.6 18.0
1.00 2.03y 0.71
278 449 41 284
56.8 25.2 24.4 10.2
1.00 0.26y 0.24y 0.09y
186 681 185
NS
208 556 238 50
25.5 27.5 39.1 22.0
1.00 1.11 1.88y 0.82
ORu
ORm
20.9 52.4
1.00 4.17y
1.00 2.44 (1.16-5.14)y
17.1 53.0
1.00 5.49y
1.00 4.07 (2.67-6.21)y
9.1 27.1
1.00 3.72y
1.00 1.98 (1.21-3.24)y
1.00 1.59 (1.10-2.29)z 0.87 (0.53-1.44)
16.0 30.5 12.9
1.00 2.30y 0.78
1.00 1.77 (1.21-2.60)y 0.95 (0.55-1.63)
1.00 0.21 (0.15-0.30)y 0.22 (0.10-0.51)y 0.09 (0.05-0.15)y
36.7 19.8 7.3 13.7
1.00 0.43y 0.14y 0.27y
1.00 0.41 (0.28-0.60)y 0.17 (0.05-0.66)y 0.39 (0.25-0.62)y
7.5 29.1 11.4
1.00 5.04y 1.57
1.00 3.64 (1.93-6.88)y 1.71 (0.78-3.73)
14.9 20.3 34.9 12.0
1.00 1.46 3.06y 0.78
1.00 1.84 (1.13-2.99)z 3.11 (1.84-5.26)y 1.10 (0.39-3.11)
1.00 1.34 (0.86-2.07) 2.21 (1.34-3.61)y 1.69 (0.70-4.11)
ORm, multivariate odds ratio obtained from stepwise logistic regression; ORu, univariate odds ratio; NS, multivariately nonsignificant variable; UN, univariately nonsignificant variable. NOTE. Sex, marital status, chances of contacting live poultry at work, and receiving comprehensive Social Security were univariately nonsignificant in both models and were not listed. *Valid percentages were reported (ie, missing values were not included in the denominator), and the frequencies therefore may not sum up to the total. y P < .01. z P < .05.
Lau et al6). Factors significantly associated with IV-related behaviors and intentions in the univariate analysis were considered in multiple stepwise logistic regression analysis. Verbal consent was sought, and ethics approval was obtained from the Chinese University of Hong Kong. RESULTS Descriptive results The participants’ socioeconomic data are summarized in Table 1. Of all participants, 95.5% (n ¼ 1,052) had heard of IV; 22.7% of these 1,052 participants thought that influenza would cause severe or very severe harm; only 14.2% had previously been recommended by health care professionals to take up IV, and less than 46.8% knew that IV is required annually. Only 28.1% of all the participants had ever taken up IV (15.2% of all participants did so during the 2005/2006 flu season); 26.8% were willing to pay more than HK $150 (market rate for IV; about USD 20) to obtain risk reductions in contracting influenza and related complications. Of those who had heard of IV, only 22.1%
intended to take up IV in the next year. Over half of those who had heard of IV believed in its efficacy in reducing the risks of infection (64.7%), influenza-related complications (51.5%), hospitalization (64.9%), and death (54.8%), whereas only 3.9% believed that it has severe adverse effects. Those who took up IV during the 2005/2006 flu season did so in private clinics (50.9%), governmental clinics (24%), or at the workplace (15%); 10.2% of them experienced some adverse effects such as having fever (33.3%) and mild pain (27.8%). The main reason for taking up the last episode of IV included influenza prevention (38.9%), being arranged by community groups such as employers/ home services/community centers/elderly centers/religious group (23.4%), and worry about contracting influenza or avian influenza (15.6%). Factors associated with IV behaviors and intention: Among those who had heard of IV The results of the multivariate analyses (model I, Table 2) showed that adults of age 30 years (odds ratio [OR], 1.91, 1.96, and 1.83 for the 3 age groups, see Table 2 for their respective 95%
J.T.F. Lau et al. / American Journal of Infection Control 40 (2012) e225-7
confidence interval [CI]), those who attended university (OR. 2.25; 95% CI: 1.22-4.17), health care professionals (OR, 2.46; 95% CI: 1.105.50), knowing that one should receive IV annually (OR, 1.59; 95% CI: 1.10-2.29), perceiving that influenza could cause severe or very severe harms (OR, 2.21; 95% CI: 1.34-3.61), and having been recommended by some health care professionals to take up IV (OR, 5.96; 95% CI: 3.82-9.30) were more likely than others to have ever taken up IV. Perception that IV has adverse effects (OR, 0.22 [severe] and 0.21 [not severe]; see Table 2 for respective 95% CI) and uncertainty about this (OR, 0.09; 95% CI: 0.05-0.15) were associated with lower likelihoods of having ever taken up IV (Table 2). Similar results were obtained on multivariate factors associated with having taken up IV in the 2005/2006 flu season (data not shown). Perceived efficacy of IV for flu prevention was significant in this case but not in model I, whereas perceived severity of influenza was significant in model I but not in this case. The multivariate model for intention to take up IV in the coming 12 months (ORs were presented under model II, Table 2) contained all cognitive variables that were significant in model I, plus knowledge that IV could reduce risks of complication and hospitalization (OR, 1.98; 95% CI: 1.21-3.24) and perceived efficacy of IV for preventing flu (OR, 3.64; 95% CI: 1.93-6.88). The variable related to “willingness to pay for an IV” was found nonsignificant in all aforementioned models (data not tabulated). DISCUSSION Approximately 30% of the participants had ever taken up IV. The prevalence of doing so in the 2005/2006 flu season (15.2%) was low and comparable with the prevalence of taking up IV in the last 12 months among American adults without any high-risk condition (10.3%).7 It is warranted to promote IV among adults in the general population, especially among younger and less-educated adults, who are less likely than others to have taken up IV. Most of the significant factors of IV identified in this study were related to the HBM, which has commonly been used to predict IV.8 The model can be used to design relevant promotion programs. Specifically, according to our findings, such programs should inform the general public about the required frequency, outcome efficacy, and adverse effects of IV and the perceived severity of influenza. Few respondents had been recommended by health care professionals to take up IV, despite the fact that family doctor’s
e227
advice is the most important factor in persuading adults to take up IV.9 Moreover, “being arranged by community groups” is a common reason to take up IV. The government, the primary care physicians, and the community should join forces in promoting IV among adults. Recall bias may exist, but it has been suggested that selfreported measure of IV history is valid.10 Individuals without a home telephone were excluded, and no causal relationship could be established in this cross-sectional survey. It is important to keep in mind that perceptions may change over time. The results of this study may serve as benchmarks for future comparisons. This study provides information that may facilitate promotion of IV among adults, which would be important at times of emerging epidemics such as H5N1. Acknowledgment The authors thank all study respondents. References 1. Neuzil KM, Reed GW, Mitchel EF, Griffin MR. Influenza-associated morbidity and mortality in young and middle-aged women. JAMA 1999;281:901-7. 2. Lee N, Chan PKS, Choi KW, Lui G, Wong B, Cockram CS, et al. Factors associated with early hospital discharge of adult influenza patients. Antivir Ther 2007;12: 501-8. 3. Nichol KL, Lind A, Margolis KL, Murdoch M, McFadden R, Hauge M, et al. The effectiveness of vaccination against influenza in healthy, working adults. New Engl J Med 1995;333:889-93. 4. Brewer NT, Chapman GB, Gibbons FX, Gerrard M, McCaul KD, Weinstein ND. Meta-analysis of the relationship between risk perception and health behavior: the example of vaccination. Health Psychol 2007;26:136-45. 5. Khalid MK, Suresh SM, Mayur MA. Determinants of adult influenza and pneumonia immunization rates. J Am Pharm Assoc 2003;43:401-11. 6. Lau JTF, Kim JH, Yang X, Tsui HY. Cross-sectional and longitudinal factors predicting influenza vaccination in Hong Kong Chinese elderly aged 65 and above. J Infect 2008;56:460-8. 7. Lu P, Bridges CB, Euler GL, Singleton JA. Influenza vaccination of recommended adult populations, US. 1989-2005. Vaccine 2008;26:1786-93. 8. Harrison JA, Mullen PD, Green LW. A meta-analysis of studies of the Health Belief Model with adults. Health Educ Res 1992;7:107-16. 9. Szucs TD, Müller D. Influenza vaccination coverage rates in five European countries: a population-based cross-sectional analysis of two consecutive influenza seasons. Vaccine 2005;23:5055-63. 10. MacDonald R, Baken L, Nelson A, Nichol KL. Validation of self-report of influenza and pneumococcal vaccination status in elderly outpatients. Am J Prev Med 1999;16:173-7.
Contents lists available at ScienceDirect
American Journal of Infection Control
American Journal of Infection Control
journal homepage: www.ajicjournal.org
Major article
Prevalence and determinants of influenza vaccination in the Hong Kong Chinese adult population Joseph T.F. Lau PhD a, b, *, Doreen W.H. Au PhD a, H.Y. Tsui PhD a, K.C. Choi PhD a a b
Centre for Health Behaviours Research, School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China Centre for Medical Anthropology and Behavioral Health, Sun Yat-sen University, Guangzhou, China
Key Words: Respiratory diseases Vaccine Coverage Perception Health Belief Model China
Background: The study examined the prevalence and associated factors of influenza vaccination (IV) among the general adult population in Hong Kong. Methods: A population-based, random telephone survey interviewed 1,102 Hong Kong Chinese adults aged 18-64 years old in 2006. Results: Of all study participants, 95.5% had heard of IV, and only 28.1% had ever received IV. Associated factors included knowledge that IV is required annually, variables related to the Health Belief Model (HBM) (eg, perceived adverse effects, perceived efficacy), and advices given by health care professionals. Conclusions: The prevalence of IV was moderately low and factors related to the HBM were found predictive of IV. Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.
Influenza causes substantial morbidity and mortality to adults of 18 to 64 years old.1 Influenza vaccination (IV) is associated with shorter duration of stay in hospital,2 lower prevalence of respiratory illnesses, and lower absenteeism from work.3 Factors derived from the Health Belief Model (HBM) such as perceived barriers, perceived benefits, and perceived severity; socioeconomic factors; health professionals’ advice; knowledge; and attitudes are significantly associated with IV.4,5 Few of these studies were conducted in Asia. METHODS An anonymous, population-based, random telephone survey was conducted during April and May 2006. Those self-reported having been diagnosed as having chronic diseases were excluded from the study. We contacted 1,594 eligible Chinese adults (18-64 years old), of whom 1,102 were interviewed. The same telephone survey method has been used in many local studies (for example, * Address correspondence to Joseph T. F. Lau, PhD, Professor, Associate Director, School of Public Health and Primary Care, Director, Centre for Health Behaviours Research, School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, 5/F, School of Public Health, Prince of Wales Hospital, Shatin, NT, Hong Kong, China. E-mail address: [email protected] (J.T.F. Lau). Supported by Department of Health, Hong Kong Special Administrative Region. Conflicts of interest: None to report.
Table 1 Sociodemographic characteristics of all participants N* Sex Male 526 Female 576 Education level Primary school or below 137 Junior/senior secondary school 553 Postsecondary or matriculation 89 University or above 319 Marital status Single 358 Married/cohabiting 727 Divorced/separated/widowed 11 Having chronic diseases Yes 91 No 1,011 Being health care professional Yes 42 No 1,060 Have chances of contacting live poultry at work Yes 21 No 1,081 Receiving comprehensive Social Security assistance (CSSA) Yes 12 No 1,077 Refused to answer 13
% 47.7 52.3 12.5 50.4 8.1 29.1 32.7 66.3 1.0 8.3 91.7 3.8 96.2 1.9 98.1 1.1 97.7 1.2
*Valid percentages were reported (ie, missing values were not included in the denominator), and the frequencies therefore may not sum up to the total.
0196-6553/$36.00 - Copyright Ó 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.ajic.2012.01.036
e226
J.T.F. Lau et al. / American Journal of Infection Control 40 (2012) e225-7
Table 2 Factors associated with influenza vaccination behavior and intention among adults who had heard of IV: N ¼ 1,052 Model I Had ever received IV n* Age group, yr 18-29 30-39 40-49 50 Education level Primary school or below Junior/senior secondary school Postsecondary or matriculation University or above Being health care professional No Yes Recommendation from health care professionals to uptake IV No Yes Knowledge that IV could reduce the risk of influenza-induced complications (eg, pneumonia) or hospitalization or death No/uncertain Yes Knowledge that IV is required every year No Yes Do not know Perceived adverse effects of IV No adverse effect Not severe Severe Do not know Perceived efficacy of IV for preventing flu Not efficacious Efficacious Do not know Perceived health impact on oneself if contracting influenza No effect/mild Moderate Severe/very severe Do not know
Model II Inclined to receive IV in the next year
%
ORu
ORm
%
242 251 303 256
23.6 35.5 30.0 28.5
1.00 1.78y 1.39 1.29
1.00 1.91 (1.17-3.09)y 1.96 (1.20-3.18)y 1.83 (1.08-3.10)z
UN
122 531 86 310
25.4 25.4 20.9 40.3
1.00 1.00 0.78 1.98y
1.00 0.98 (0.56-1.74) 0.93 (0.41-2.10) 2.25 (1.22-4.17)y
UN
1,010 42
27.8 69.0
1.00 5.79y
1.00 2.46 (1.10-5.50)y
903 149
22.8 69.8
1.00 7.82y
1.00 5.96 (3.82-9.30)y
287 765
UN
343 492 217
23.6 38.6 18.0
1.00 2.03y 0.71
278 449 41 284
56.8 25.2 24.4 10.2
1.00 0.26y 0.24y 0.09y
186 681 185
NS
208 556 238 50
25.5 27.5 39.1 22.0
1.00 1.11 1.88y 0.82
ORu
ORm
20.9 52.4
1.00 4.17y
1.00 2.44 (1.16-5.14)y
17.1 53.0
1.00 5.49y
1.00 4.07 (2.67-6.21)y
9.1 27.1
1.00 3.72y
1.00 1.98 (1.21-3.24)y
1.00 1.59 (1.10-2.29)z 0.87 (0.53-1.44)
16.0 30.5 12.9
1.00 2.30y 0.78
1.00 1.77 (1.21-2.60)y 0.95 (0.55-1.63)
1.00 0.21 (0.15-0.30)y 0.22 (0.10-0.51)y 0.09 (0.05-0.15)y
36.7 19.8 7.3 13.7
1.00 0.43y 0.14y 0.27y
1.00 0.41 (0.28-0.60)y 0.17 (0.05-0.66)y 0.39 (0.25-0.62)y
7.5 29.1 11.4
1.00 5.04y 1.57
1.00 3.64 (1.93-6.88)y 1.71 (0.78-3.73)
14.9 20.3 34.9 12.0
1.00 1.46 3.06y 0.78
1.00 1.84 (1.13-2.99)z 3.11 (1.84-5.26)y 1.10 (0.39-3.11)
1.00 1.34 (0.86-2.07) 2.21 (1.34-3.61)y 1.69 (0.70-4.11)
ORm, multivariate odds ratio obtained from stepwise logistic regression; ORu, univariate odds ratio; NS, multivariately nonsignificant variable; UN, univariately nonsignificant variable. NOTE. Sex, marital status, chances of contacting live poultry at work, and receiving comprehensive Social Security were univariately nonsignificant in both models and were not listed. *Valid percentages were reported (ie, missing values were not included in the denominator), and the frequencies therefore may not sum up to the total. y P < .01. z P < .05.
Lau et al6). Factors significantly associated with IV-related behaviors and intentions in the univariate analysis were considered in multiple stepwise logistic regression analysis. Verbal consent was sought, and ethics approval was obtained from the Chinese University of Hong Kong. RESULTS Descriptive results The participants’ socioeconomic data are summarized in Table 1. Of all participants, 95.5% (n ¼ 1,052) had heard of IV; 22.7% of these 1,052 participants thought that influenza would cause severe or very severe harm; only 14.2% had previously been recommended by health care professionals to take up IV, and less than 46.8% knew that IV is required annually. Only 28.1% of all the participants had ever taken up IV (15.2% of all participants did so during the 2005/2006 flu season); 26.8% were willing to pay more than HK $150 (market rate for IV; about USD 20) to obtain risk reductions in contracting influenza and related complications. Of those who had heard of IV, only 22.1%
intended to take up IV in the next year. Over half of those who had heard of IV believed in its efficacy in reducing the risks of infection (64.7%), influenza-related complications (51.5%), hospitalization (64.9%), and death (54.8%), whereas only 3.9% believed that it has severe adverse effects. Those who took up IV during the 2005/2006 flu season did so in private clinics (50.9%), governmental clinics (24%), or at the workplace (15%); 10.2% of them experienced some adverse effects such as having fever (33.3%) and mild pain (27.8%). The main reason for taking up the last episode of IV included influenza prevention (38.9%), being arranged by community groups such as employers/ home services/community centers/elderly centers/religious group (23.4%), and worry about contracting influenza or avian influenza (15.6%). Factors associated with IV behaviors and intention: Among those who had heard of IV The results of the multivariate analyses (model I, Table 2) showed that adults of age 30 years (odds ratio [OR], 1.91, 1.96, and 1.83 for the 3 age groups, see Table 2 for their respective 95%
J.T.F. Lau et al. / American Journal of Infection Control 40 (2012) e225-7
confidence interval [CI]), those who attended university (OR. 2.25; 95% CI: 1.22-4.17), health care professionals (OR, 2.46; 95% CI: 1.105.50), knowing that one should receive IV annually (OR, 1.59; 95% CI: 1.10-2.29), perceiving that influenza could cause severe or very severe harms (OR, 2.21; 95% CI: 1.34-3.61), and having been recommended by some health care professionals to take up IV (OR, 5.96; 95% CI: 3.82-9.30) were more likely than others to have ever taken up IV. Perception that IV has adverse effects (OR, 0.22 [severe] and 0.21 [not severe]; see Table 2 for respective 95% CI) and uncertainty about this (OR, 0.09; 95% CI: 0.05-0.15) were associated with lower likelihoods of having ever taken up IV (Table 2). Similar results were obtained on multivariate factors associated with having taken up IV in the 2005/2006 flu season (data not shown). Perceived efficacy of IV for flu prevention was significant in this case but not in model I, whereas perceived severity of influenza was significant in model I but not in this case. The multivariate model for intention to take up IV in the coming 12 months (ORs were presented under model II, Table 2) contained all cognitive variables that were significant in model I, plus knowledge that IV could reduce risks of complication and hospitalization (OR, 1.98; 95% CI: 1.21-3.24) and perceived efficacy of IV for preventing flu (OR, 3.64; 95% CI: 1.93-6.88). The variable related to “willingness to pay for an IV” was found nonsignificant in all aforementioned models (data not tabulated). DISCUSSION Approximately 30% of the participants had ever taken up IV. The prevalence of doing so in the 2005/2006 flu season (15.2%) was low and comparable with the prevalence of taking up IV in the last 12 months among American adults without any high-risk condition (10.3%).7 It is warranted to promote IV among adults in the general population, especially among younger and less-educated adults, who are less likely than others to have taken up IV. Most of the significant factors of IV identified in this study were related to the HBM, which has commonly been used to predict IV.8 The model can be used to design relevant promotion programs. Specifically, according to our findings, such programs should inform the general public about the required frequency, outcome efficacy, and adverse effects of IV and the perceived severity of influenza. Few respondents had been recommended by health care professionals to take up IV, despite the fact that family doctor’s
e227
advice is the most important factor in persuading adults to take up IV.9 Moreover, “being arranged by community groups” is a common reason to take up IV. The government, the primary care physicians, and the community should join forces in promoting IV among adults. Recall bias may exist, but it has been suggested that selfreported measure of IV history is valid.10 Individuals without a home telephone were excluded, and no causal relationship could be established in this cross-sectional survey. It is important to keep in mind that perceptions may change over time. The results of this study may serve as benchmarks for future comparisons. This study provides information that may facilitate promotion of IV among adults, which would be important at times of emerging epidemics such as H5N1. Acknowledgment The authors thank all study respondents. References 1. Neuzil KM, Reed GW, Mitchel EF, Griffin MR. Influenza-associated morbidity and mortality in young and middle-aged women. JAMA 1999;281:901-7. 2. Lee N, Chan PKS, Choi KW, Lui G, Wong B, Cockram CS, et al. Factors associated with early hospital discharge of adult influenza patients. Antivir Ther 2007;12: 501-8. 3. Nichol KL, Lind A, Margolis KL, Murdoch M, McFadden R, Hauge M, et al. The effectiveness of vaccination against influenza in healthy, working adults. New Engl J Med 1995;333:889-93. 4. Brewer NT, Chapman GB, Gibbons FX, Gerrard M, McCaul KD, Weinstein ND. Meta-analysis of the relationship between risk perception and health behavior: the example of vaccination. Health Psychol 2007;26:136-45. 5. Khalid MK, Suresh SM, Mayur MA. Determinants of adult influenza and pneumonia immunization rates. J Am Pharm Assoc 2003;43:401-11. 6. Lau JTF, Kim JH, Yang X, Tsui HY. Cross-sectional and longitudinal factors predicting influenza vaccination in Hong Kong Chinese elderly aged 65 and above. J Infect 2008;56:460-8. 7. Lu P, Bridges CB, Euler GL, Singleton JA. Influenza vaccination of recommended adult populations, US. 1989-2005. Vaccine 2008;26:1786-93. 8. Harrison JA, Mullen PD, Green LW. A meta-analysis of studies of the Health Belief Model with adults. Health Educ Res 1992;7:107-16. 9. Szucs TD, Müller D. Influenza vaccination coverage rates in five European countries: a population-based cross-sectional analysis of two consecutive influenza seasons. Vaccine 2005;23:5055-63. 10. MacDonald R, Baken L, Nelson A, Nichol KL. Validation of self-report of influenza and pneumococcal vaccination status in elderly outpatients. Am J Prev Med 1999;16:173-7.