http://orcid.org/0000-0002-7082-2224
ABSTRACT
Objectives: Very low uptake has been noted for influenza vaccination in the province of Quebec. This study aimed to identify the determinants of influenza vaccination among a large regional population. Methods: A telephone survey was administered to a random digit sample in the Eastern Townships region (Quebec, Canada). Respondents were asked questions on several health topics such as perceived knowledge and beliefs about influenza immunization, medical consultations, perceived health status and life habits. Significant variables in the univariate analysis were introduced into a multivariate logistic regression model to determine independent factors for having received the influenza vaccine (aOR and 95% CI) among adults aged ≥60 years and younger adults with ≥1 chronic condition. Results: A total of 4,620 interviews were analyzed. Among the target groups, 55.4% of adults aged ≥60 and 32.2% of adults aged 18–59 with at least one chronic disease had received the influenza vaccine during the 2013–2014 season. Several determinants were significantly associated with influenza vaccination in both groups such as having received a recommendation from a healthcare professional. Among adults aged ≥60, not having consulted a chiropractor over the last 12 months (aOR = 2.37; 1.09-5.19), non-smokers (aOR = 1.78; 1.22-2.59) and self-perceived poor health status (aOR = 1.45; 1.01-2.06) were significantly linked to flu vaccination. In the younger group, influenza vaccination was independently associated to low alcohol consumption (aOR = 2.14; 1.13-4.05) and being overweight (aOR = 1.63; 1.12-2.38). Conclusions: Many determinants influence the decision to get vaccinated against influenza. Specific messages should be tailored for high-risk groups to effectively increase influenza vaccine coverage.
Introduction
Every year, influenza infections cause an average of 12,000 hospitalizations and 3,500 deaths in Canada.Citation1,Citation2 In the province of Quebec (Canada), the estimated rate of hospitalization attributable to influenza ranges from 16.9 to 71.5/100 000 adults per season.Citation3 Influenza vaccination is offered free of charge in Quebec through a provincial and publicly-funded program that targets specific groups with a high risk of complications: infants aged between 6 and 23 months, adults aged ≥60, adults and children suffering from a chronic condition, and pregnant women in their second or third trimester.Citation4 Healthcare professionals are also targeted to reduce transmissions to patients.Citation4 However, influenza vaccine coverage in these target groups is low and still does not reach the national objective of 80% for the group of adults aged 18–59 with ≥1 chronic condition.Citation5,Citation6 According to the latest available data in Quebec, 57% of adults aged ≥60 and 33% of adults aged 18–59 and suffering from a chronic medical condition were vaccinated against influenza during the 2013–2014 season.Citation5,Citation6 This suboptimal vaccination coverage is problematic and highlights the need for effective strategies to increase influenza vaccination. Before the development of such strategies, it is imperative that we better understand the factors influencing the decision to get vaccinated against influenza. Thus, the present study aims to identify the independent determinants of influenza vaccine uptake in a large regional sample in the province of Quebec among two high-risk groups: adults ≥60 years and adults aged 18–59 with ≥1 chronic disease.
Results
A total of 8,737 individuals completed the questionnaire, for a participation rate of 48.3%. Among these, 7 205 (82.5%), 820 (9.4%) and 712 (8.1%) answered the questionnaire by phone, online and by cellphone, respectively. As for the two target groups targeted by the influenza vaccination program (our study population), 2,880 respondents were aged ≥60 while 1,740 were aged 18–59 and suffered from a chronic condition.
In all, 55.4%adults aged ≥60 years and 32.2% of adults aged 18 to 59 with ≥1 chronic condition had received the influenza vaccine during the previous season.
Among people aged ≥60, a higher proportion of those who were vaccinated against influenza were aged 80 or over (14.3% vs 8.0%, p < 0.001) and lived in the main metropolitan area (Sherbrooke) (52.3% vs 47.7%, p = 0.013) while a lower proportion of vaccinated people had a low household income (35.9% vs 40.7%, p = 0.033) and spoke French at home (90.2% vs 93.1%, p = 0.006) ().
Table 1. Demographic and socioeconomic characteristics of respondents aged ≥60 according to vaccination status, Eastern Townships, 2014.
Adults aged 18–59 with at least one chronic condition presented more significant differences in socioeconomic characteristics between influenza vaccinated and unvaccinated groups (). When compared to unvaccinated individuals, there were higher proportions of women (54.1% vs 48.5%, p = 0.028), of people aged 50 to 59 years (45.6% vs 37.8%, p = 0.011), of university graduates (39.5% vs 28.4%, p < 0.001), of high household income earners (34.8% vs 22.5%, p < 0.001) and people living in a couple (64.3% vs 59.6%, p = 0.041) in the vaccinated group. As observed for people aged ≥60, a lower proportion of vaccinated individuals aged 18–59 with ≥1 chronic condition spoke French at home (92.8% vs 95.4%, p = 0.026).
Table 2. Demographic and socioeconomic characteristics of respondents aged 18 to 59 years old with ≥1 chronic condition, according to vaccination status, Eastern Townships, 2014.
In the multivariate analyses, several determinants of influenza vaccination were identified among the two target groups (). Having received a recommendation from a healthcare professional to get the flu vaccine was the factor most strongly associated with influenza vaccination among adults aged ≥60 (aOR = 5.82; 4.43-7.66) as well as among younger adults with ≥1 chronic condition (aOR = 4.20; 2.97-5.95). Most of the HBM items were significant determinants of influenza vaccination in both groups, except for perceived vaccine risks that did not remain significant in the second group. Perceived severity of the disease presented opposite results. The belief that getting the flu causes severe health complications was significantly associated with higher odds of vaccination among adults aged ≥60 (aOR = 1.40; 1.01-1.94) and among younger adults with ≥1 chronic condition (aOR = 1.65; 1.09-2.51). The belief that catching the flu impacts daily activities was rather associated with lower odds of vaccination among the same groups, respectively (aOR = 0.76; 0.54-1.08, aOR = 0.57; 0.36-0.88). Perceived sufficient knowledge about vaccination did not remain statistically significant after controlling for other variables in the two study groups.
Table 3. Determinants of influenza vaccination among adults ≥60 years and adults aged 18 to 59 with ≥1 chronic condition, Eastern Townships, 2014.
With regards to healthcare consultations over the past 12 months, having consulted a conventional medicine practitioner was linked to influenza vaccine uptake, as observed with consultations with family doctors (aOR = 1.48; 1.03-2.12) and with nurses (aOR = 1.35; 1.01-1.82) in the elderly. Conversely, having consulted an alternative medicine practitioner was associated with lower odds of influenza vaccination among that population (aOR = 0.42; 0.19-0.92).
Specific health status characteristics and life habits showed a significant association with influenza vaccination in both groups. In the elderly, self-perceived poor health status (aOR = 1.45; 1.01-2.06) was significantly linked to flu vaccination while smoking cigarettes was associated with lower odds of vaccination (aOR = 0.56; 0.39-0.82). In the other group, being overweigth (aOR = 1.63; 1.12-2.38) and excessive alcohol consumption (5 or more alcoholic drinks on one occasion per week) (aOR = 0.47; 0.25-0.89) were independently associated with higher and lower odds of influenza vaccination, respectively.
Finally, two socioeconomic variables were identified as independent factors of influenza vaccination: being retired among the adults aged ≥60 (aOR = 1.63; 1.17-2.27) and being a healthcare professional among the adults <60 years with ≥1 chronic condition (aOR = 3.08; 1.67-5.66).
Discussion
This study allowed for the identification of several determinants of influenza vaccination for two specific groups targeted by the publicly-funded provincial vaccination program. In our knowledge, this is the first Canadian study to perform an extensive analysis on determinants of influenza vaccination, particularly among adults suffering from a chronic condition. The large study sample and the exhaustive analysis allowed identifying determinants in the elderly and the adults with a chronic disease in a specific region of Quebec. The study of these determinants is important in order to develop appropriate strategies that aim to increase influenza vaccine coverage in these risk groups.
Our vaccine coverage results are similar to those documented in the 2014 Quebec Survey on Influenza Vaccination (55% vs 57% of vaccinated adults aged ≥60 years and 32% vs 33% of vaccinated adults aged 18–59 suffering from a chronic condition, respectively).Citation5,Citation6
Our results on influenza vaccination determinants are also consistent with several other studies that also demonstrated relationships between variables from the HBM and influenza vaccination.Citation9,Citation11,Citation12 People who are favorable to influenza vaccination may feel susceptible to the disease, and may believe in the effectiveness and safety of the vaccine. They might be especially aware that the risks of non-vaccination are higher than the risks associated with vaccination. However, we found that individuals who perceived that influenza could impact daily activities was instead associated with non-vaccination against the flu. It seems like even if vaccinated people believe that the flu causes severe health complications, they also think that if they catch the flu, it will not prevent them from doing their daily activities. This could be related to the perception that influenza is a benign and mild problem and this determinant is therefore not a factor motivating influenza vaccination.
As described in other studies,Citation13,Citation14 having received a recommendation from a healthcare professional is a strong determinant of influenza vaccination. We also found that having consulted a conventional healthcare professional over the last 12 months, such as a family doctor or a nurse was linked to influenza vaccination. This result is consistent with other studies also showing that having consulted a physician in the past 12 months and having a regular family doctor were independent predictors of seasonal influenza vaccine uptake.Citation15,Citation16 In the same way, consultation with chiropractors was associated to a lower likelihood of influenza vaccination. A Canadian study found similar results: women who received influenza vaccination in the past 12 months were significantly more likely to have consulted a family doctor and significantly less likely to have consulted a chiropractor or a homeopath/naturopath.Citation17
Self-perceived health status and several life habits were identified as determinants of influenza vaccination. Among adults aged ≥60 years, poor self-perceived health status and non-smoking were significant determinants. A systematic review of influenza vaccination in elderly people identified self-reported poor health status and concomitant chronic illness as predictors of influenza vaccination.Citation15 In a study using a large U.S. sample of adults aged ≥50 years, smoking status was also found to be a factor influencing the odds of receiving influenza vaccination: current smokers were less likely to have received the influenza vaccine in the past year compared to individuals who had never smoked.Citation18 Authors suggested that smokers may be less concerned with health issues such as immunization, which would explaining why smokers are less likely to be vaccinated against the flu.
Among adults <60 years and suffering from at least one chronic condition, we found that having a body mass index ≥30 kg/m2 and a low alcohol consumption were associated with influenza vaccine uptake. According to a meta-analysis, combined findings from several studies suggest that overweight adults are more likely to be vaccinated against influenza.Citation19 Authors explained that adults with obesity are generally more counseled about the risks of obesity-related disease, which suggests that they might perceive a higher personal risk of future disease than non-obese individuals. People with obesity also tend to suffer from other chronic diseases for which vaccination is recommended. In a Canadian population-based survey, increased alcohol consumption was associated with lower odds of influenza vaccination in the past 12 months, which is consistent with our findings among the second target group.Citation20
Only two demographic or socioeconomic variables remained significantly associated with influenza vaccine uptake when introduced into multivariate analyses. Adults aged ≥60 years who did not work full time or part time were more likely to be vaccinated against the flu. Indeed, being retired was associated with influenza vaccination uptake in previous studies.Citation16,Citation21 In the other high-risk group, being a healthcare professional was a strong predictor of influenza vaccination as expected, given that healthcare professionals are specifically targeted by the influenza vaccination program.
Since specific vaccination determinants were identified for each study group, this suggests that a “one message fits all” approach will not be sufficient to promote influenza vaccination.Citation22 Tailored messages and strategies should be put in place to effectively promote vaccination among specific populations.Citation23 For the elderly, targeted interventions could particularly aid in the promotion of influenza vaccination among individuals who consult alternative medicine practitioners such as chiropractors, and among smokers. On the other hand, individuals who perceived themselves as being in good health and who still work full time or part time should receive a different promotion message. In the case of younger adults with ≥1 chronic condition, non-obese people could benefit from a recommendation and individuals who have a higher frequency of alcohol consumption should be particularly targeted. A complementary strategy could be promoting these tailored messages in specific locations frequented by some of these population profiles (e.g. tobacco cessation clinics, outpatient clinics treating people with chronic disease, etc.). Moreover, recommendations from healthcare professionals and consultation with family doctors and nurses were found to be independent determinants of vaccination uptake. As such, strategies should also focus on promoting the role of healthcare professionals in the recommendation of influenza vaccination.
One of the main strengths of this study was the inclusion and analysis of numerous variables related to the socioeconomic and demographic situation of respondents and to several health topics such as physician consultation, perceived health status and life habits in a large population-based sample. Studies using telephone surveys usually cannot reach people who have no home phone. However, in our study, people with cellphones were also contacted, which reduced the inherent selection bias generated by this type of study. An online questionnaire was also available to accommodate more participants.
However, the present study did also have some limits. First, due to its cross-sectional design, this study is unable to establish a straight cause-effect relationship between influenza vaccination and the observed determinants. In spite of the recruitment procedure that implied first calling the participant to make an appointment and later answering the survey, the study's participation rate was quite high. Selection bias was, however, unavoidable in this study design, which means that non-respondents could have different opinions about immunization compared to respondents. That being said, weighting methods and the fact that this was a general survey about health, rather than a more problematic immunisation-specific survey, partially reduced this non-response bias. Weighted data was used in all analyses to ensure the generalization of our findings for the population of the Eastern Townships.
Influenza vaccination status was self-reported and based on recall which may have led to some misclassification. If so, the misclassification should be non-differential and would decrease our capacity in finding relevant determinants. However, previous studies have demonstrated that self-reporting influenza vaccination is highly sensitive and moderately specific when compared to medical record documentation.Citation24
Methods
Design and sample
A cross-sectional study about health determinants was conducted between June and October 2014 among adults living in the Eastern Townships region (Quebec, Canada). A phone survey was administered to a large random digit sample by trained interviewing staff. Cellphone numbers were also included into the random digit dialing. The sample was stratified according to the place of residence, with half of the sample living in Sherbrooke, the region's main city. Adults 18 years and over, living in a private household and speaking French or English were eligible to participate in the study. During the study period, a total of 148 trained interviewers from the “Bureau d'interviewers professionnels” (BIP) called between 10:00 am and 9:00 pm on weekdays and 3:00 pm to 9:00 pm on Sundays to ascertain the respondent's eligibility and to schedule an appointment to answer the survey. Interviewers then conducted computer-assisted telephone interviews based on a structured questionnaire on weekdays between 8:30 am and 5:00 pm. An online version of the questionnaire was also available to respondents.
Survey questionnaire
A questionnaire was developed to assess several health topics among the population. Questions were mostly based on validated questionnaires and were determined with the collaboration of university researchers associated with the Eastern Townships Health Authority. Relevant items, such as questions about consultations with health professionals, perceived health status, life habits and socioeconomic situation, were considered in this analysis in order to identify independent determinants of influenza vaccination.
Items about immunization knowledge, attitudes and beliefs were based upon the Health Belief Model (HBM), an established theoretical framework used to examine patient motivations for adapting a preventive health-related behavior,Citation7" and were developed by immunization experts from the Eastern Townships Public Health Department. The HBM has previously been used in several studies to assess immunization beliefs and behaviors.Citation8,Citation9,Citation10 Based upon this model, four components were assessed in the present study: perceived susceptibility (i.e. the respondent's beliefs about their risk of contracting influenza), perceived severity (i.e. the respondent's concerns about the seriousness of influenza and its consequences), perceived vaccine benefits and perceived vaccine risks. The main outcome of the study was the self-reported vaccination status for the influenza vaccine during the previous (2013-2014) season, i.e. since October 2013.
Items mainly used a 4-point Likert scale and the questionnaire was pre-tested in the beginning of June 2014. The study was approved by the CSSS-IUGS Research Ethics Board.
Statistical analyses
Data were weighted according to age, sex, and place of residence using an iterative method in order to represent the population of the Eastern Townships. Data collected via landline telephone, cellular telephone and online were analyzed and presented together. Likert-scaled responses were analyzed as dichotomous variables indicating the respondent's agreement or lack of agreement with the item (e.g., totally/somewhat agree vs totally/somewhat disagree). Chi-square tests were performed to explore differences in participant responses between immunized and non-immunized respondents. Participants with missing values for one or more study variables were excluded only in the analyses involving those variables. Responses of “I don't know” or “Preferred to not answer” were considered as missing and were thus not included in the analyses.
Univariate logistic regressions were first performed in order to examine each variable individually without adjusting for the effects of others. All statistically significant variables associated to vaccine uptake in univariate analysis for a significance level set at 0.05 were then introduced into the final multivariate model in order to identify independent determinants of influenza vaccination. Adjusted odds ratios (aOR) and their respective 95% confidence intervals (95% CI) were calculated. All analyses were conducted using SPSS version 20.0 and were performed on the two target populations: 1) adults aged ≥60 years, and 2) adults aged 18–59 having ≥1 chronic disease, such as asthma, chronic bronchitis, emphysema, chronic obstructive pulmonary disease, diabetes, cardiac disease or cancer.
Conclusions
In addition to beliefs and attitudes towards influenza vaccination, consultation with healthcare professionals, life habits and socioeconomic variables should be taken into account when promoting influenza vaccination. Given those results, messages and promotion strategies should be tailored for specific high-risk groups to effectively increase influenza vaccine coverage.
Abbreviations
| aOR | = | adjusted odds ratio |
| CI | = | confidence intervals |
| HBM | = | Health Belief Model |
| VPD | = | vaccine-preventable diseases |
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
Author contributions
Dr Maryse Guay, Dr Geneviève Baron, Dr Geneviève Petit and Dr Arnaud Gagneur participated in the study design, in the selection of questions on immunization for the survey questionnaire and in the interpretation of the data. They reviewed/edited, and approved the final manuscript as submitted.
Virginie Gosselin performed data analysis and participated in data interpretation. She wrote and reviewed/edited the manuscript, and approved the final manuscript as submitted.
All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.
Acknowledgments
We thank the BIP staff for conducting all the interviews and all the participants of the study. We also thank Dr. Marie-France Langlois for giving us access to the survey data about consultations of healthcare professionals over the last 12 months and Jade Berbari for English revision of the manuscript
Additional information
Funding
References
- Schanzer DL, McGeer A and Morris K. Statistical estimates of respiratory admissions attributable to seasonal and pandemic influenza for Canada. Influenza Other Respir Viruses 2013;7(5):799–808. doi:10.1111/irv.12011.
- Schanzer DL, Sevenhuysen C, Winchester B and Mersereau T. Estimating influenza deaths in Canada, 1992–2009. PLoS One 2013;8(11):e80481. eCollection 2013. doi:10.1371/journal.pone.0080481.
- Gilca R, Douville-Fradet M, Amini R, De Serres G, Boulianne N. Estimation des hospitalisations attribuables à l'influenza selon différentes méthodes. 2016. Institut national de santé publique du Québec : Québec. 14 p.
- Ministère de la Santé et des Services sociaux. Protocole d'immunisation du Québec, édition mai 2013. 2016. Gouvernement du Québec : Québec. 505 p.
- Dubé È, Gagnon D, Zhou Z, Guay M, Boulianne N, Sauvageau C, Landry M, Markowski F, Turmel B. Enquête québécoise sur la vaccination contre la grippe saisonnière et le pneumoccoque. 2015. Institut national de santé publique du Québec : Québec. 85 p.
- Dubé E, Gagnon D, Kiely M, Defay F, Guay M, Boulianne N, Sauvageau C, Landry M, Turmel B, Markowski F, et al.. Seasonal influenza vaccination uptake in Quebec, Canada, 2 years after the influenza A(H1N1) pandemic. Am J Infect Control 2014;42(5):e55–9. doi:10.1016/j.ajic.2014.01.006.
- Gust DA, Darling N, Kennedy A, Schwartz B. Parents with doubts about vaccines: which vaccines and reasons why. Pediatrics 2008;122(4):718–25. doi:10.1542/peds.2007-0538.
- Rosenstock IM. Historical origins of the health belief model. Health Education Monographs 1974;2(4):328–35. doi:10.1177/109019817400200403.
- Coe AB, Gatewood SBS, Moczygemba LR, Goode JVR, Beckner JO. The use of the health belief model to assess predictors of intent to receive the novel (2009) H1N1 influenza vaccine. Inov Pharm 2012;3(2):1–11. doi:10.24926/iip.v3i2.257.
- Lyn-Cook R, Halm EA, Wisnivesky JP. Determinants of adherence to influenza vaccination among inner-city adults with persistent asthma. Prim Care Resp J 2007;16(4):229–35.
- Chen MF, Wang RH, Schneider JK, Tsai CT, Jiang DD, Hung MN, Lin LJ. Using the Health Belief Model to understand caregiver factors influencing childhood influenza vaccinations. J Community Health Nurs 2011;28(1):29–40. doi:10.1080/07370016.2011.539087.
- Nexøe J, Kragstrup J, Søgaard J. Decision on influenza vaccination among the elderly. A questionnaire study based on the Health Belief Model and the Multidimensional Locus of Control Theory. Scand J Prim Health Care 1999;17(2):105–10. doi:10.1080/028134399750002737.
- Fabry P, Gagneur A, Pasquier JC. Determinants of A (H1N1) vaccination: cross-sectional study in a population of pregnant women in Quebec. Vaccine 2011;29(9):1824–9. doi:10.1016/j.vaccine.2010.12.109.
- Wu S, Su J, Yang P, Zhang H, Li H, Chu Y, Hua W, Li C, Tang Y, Wang Q. Factors associated with the uptake of seasonal influenza vaccination in older and younger adults: a large, population-based survey in Beijing, China. BMJ Open 2017;7(9):e017459. doi:10.1136/bmjopen-2017-017459.
- Kohlhammer Y, Schnoor M, Schwartz M, Raspe H, Schäfer T. Determinants of influenza and pneumococcal vaccination in elderly people: a systematic review. Public Health 2007;121(10):742–51. doi:10.1016/j.puhe.2007.02.011.
- Böhmer MM, Walter D, Krause G, Müters S, Gösswald A, Wichmann O. Determinants of tetanus and seasonal influenza vaccine uptake in adults living in Germany. Hum Vaccin 2011;7(12):1317–25. doi:10.4161/hv.7.12.18130.
- Chambers CT, Bluxton JA, Koehoorn M. Consultation with health care professionals and influenza immunization among women in contact with young children. Can J Public Health 2010;101(1):15–9.
- Pearson WS, Dube SR, Ford ES, Mokdad AH. Influenza and pneumococcal vaccination rates among smokers: data from the 2006 behavioral risk factor surveillance. Syst Prev Med 2009;48:180–3. doi:10.1016/j.ypmed.2008.11.001.
- Harris JA, Moniz MH, Iott B, Power R, Griggs JJ. Obesity and the receipt of influenza and pneumococcal vaccination: a systematic review and meta-analysis. BMC Obes 2016;3:24. doi:10.1186/s40608-016-0105-5.
- Li Z, Doan Q, Dobson S. Determinants of influenza immunization uptake in Canadian youths. Vaccine 2010;28(19):3462–6. doi:10.1016/j.vaccine.2010.02.068.
- Nessler K, Krztoń-Królewiecka A, Chmielowiec T, Jarczewska D, Windak A. Determinants of influenza vaccination coverage rates among primary care patients in Krakow, Poland and the surrounding region. Vaccine 2014;32(52):7122–7. doi:10.1016/j.vaccine.2014.10.026.
- Jones TF, Ingram LA, Craig AS, Schaffner W. Determinants of influenza vaccination, 2003–2004: Shortages, fallacies and disparities. Clin Infect Dis 2004;39(12):1824–8. doi:10.1086/427153.
- Dubé E, Gagnon D, Audet D, Bradet R, Boulianne N, Guay M, Sauvageau C. Promoting vaccination: implementation of targeted interventions to enhance access to vaccination services in Quebec (Canada). Public Health 2015;129(12):1627–9. doi:10.1016/j.puhe.2015.07.013.
- 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(3):173–7. doi:10.1016/S0749-3797(98)00159-7.