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Attitudes and perceptions of influenza vaccination among Hong Kong doctors and medical students before the 2009 pandemic

Kwok Kei Mak, Yuen Fung Yiu, Kwan Lung Ko, Kenneth Siu Hung Hui, Kin Mei Mak, Lung Yi Mak, Wai Pan To, King Hung Wu, Fanny Yeung, Pamela Pui Wah Lee
DOI: http://dx.doi.org/10.1093/eurpub/cks014 257-262 First published online: 1 March 2012

Abstract

Background: Vaccination is an important preventive measure for preparing against the influenza pandemics. This study investigated the attitudes and perceptions of influenza vaccination among doctors and medical students in Hong Kong. Methods: A cross-sectional survey was conducted among 204 doctors and 242 medical students in a teaching hospital in 2009. Participants’ demographic and job characteristics, and influenza experience and vaccination in the previous year were assessed in the questionnaire. Logistic regression models were used to examine the associations between uptake of influenza vaccination and the perceived benefits. Results: Medical students were more likely to have receive an influenza vaccination in the previous year (66.9 vs. 39.7%) and acknowledged the related benefits than doctors. Moreover, uptake of influenza vaccine was associated with perceived benefits of vaccination in both doctors and medical students. Conclusions: The perceived benefits of influenza vaccination are an important factor in vaccine uptake for both doctors and medical students in Hong Kong, and should be reinforced in the professional training.

Introduction

Influenza is a highly infectious viral disease, leading to substantial morbidity and mortality every year.1,2 Health Care Professionals (HCP) frequently in contact with patients are vulnerable to the exposure of influenza virus infection. A previous study demonstrated that 23% of HCP had serological evidence of influenza virus infection during the influenza seasons.3 However, many of these subclinical infections may not be noticed by the HCP themselves.4 The Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) has recommended annual influenza vaccination as a core preparation measure for HCP.5 Influenza vaccination could reduce 70–90% of influenza incidence in healthy adults.6 In addition to self-protection,7 vaccination among HCP could also lower the communicable risks of influenza from HCP to patients, especially the special groups such as those with chronic diseases,8,9 and infants.10 Although influenza vaccination is shown to be effective in the prevention of infection, acceptance of vaccines among HCP was low in many countries.11 The reported vaccination rate was ∼40% in Germany12 and Spain,13 17% in Greece14 and only ∼10% in China.15

In Hong Kong, influenza is one of the major causes of hospitalization among children and the elderly during the peak seasons, January–March and July–August.16,17 Free vaccines have been provided to HCP during influenza seasons under the Hong Kong Government Influenza Vaccination Program (GIVP), but the uptake rate among HCP in the Years 2008–09 was only 32%.18 Similar to HCP, medical students were also given priority to receive influenza vaccines through the university health clinic. Information about the prevalence of influenza vaccination among medical students is not yet available.

The perceptions of influenza vaccination of HCP which were associated with vaccine uptake included the perceived effectiveness of preventing infection of themselves19 and relatives,20 the perceived side effects14 and the perceived efficacy21,22 of vaccination. Economic factors were not found to be associated with vaccination for HCP.23 Most of these studies did not include medical students who also had frequent contact with patients. This study aimed to investigate the prevalence of influenza vaccine uptake and its association with perception of benefits of vaccination among Hong Kong doctors and medical students.

Methods

A cross-sectional survey was conducted among 204 doctors in the clinical departments and 242 medical students under clinical training (Years 3–5) in a teaching hospital with 1500 beds and 4500 staff in Hong Kong before the 2009 Influenza A (H1N1) pandemic (February–March 2009). With no previously reported prevalence of influenza vaccination among medical students, we calculated our sample size based on the previous report of prevalence (∼30%) in Hong Kong HCP. A sample size of 200 for each group was required to achieve a power of 80% and a confidence level of 95%, representing the medical doctor population in Hong Kong, which was about 9000. Invitation letters were sent to the chairs of clinical departments for their approval to distribute the questionnaires to doctors. Participating doctors completed their questionnaires after departmental meetings and returned them to the investigators via their departments. In addition, Years 3–5 medical students were invited to complete the questionnaire after a lecture. All participation was voluntary and ethical approval was granted by the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster.

The questionnaire consisted of items on demographic characteristics including sex, age, living with dependents (yes/no); job characteristics including department (surgical, non-surgical), position (internship/resident/associate consultant/consultant), daily patient contact time (doctors: <8 h/≥8 h; students: <2 h/≥2 h) and year of study (Year 3/Year 4/Year 5). Moreover, questions for assessing their experiences of influenza were the number of upper respiratory tract infections (URTI) in the past 12 months (0–2 times/≥3 times) and sick leaves due to URTI in the past 12 months (none/any). In addition, uptake of influenza vaccine in the previous year (yes/no) was assessed.

The items of perception towards influenza vaccination were ‘Influenza vaccine can protect me from influenza infection’, ‘Getting myself vaccinated can protect my relatives from influenza infection’, ‘The benefits of influenza vaccine outweigh its side effects’, ‘Influenza vaccine can alleviate influenza symptoms when I have influenza’, ‘Healthcare workers have the professional responsibility to receive influenza vaccine’ and ‘Getting myself vaccinated can protect my patients from influenza infection’.

Descriptive statistics were used to present the demographic and job characteristics, as well as the influenza experience. Cronbach's α was used to determine the internal reliability of the six items for assessing the perceptions of influenza vaccination. Differences of the perceptions of influenza vaccination between doctors and medical students were examined by the Pearson's χ2 test. Furthermore, the odds ratio (OR) of influenza vaccine uptake in the previous year for each of the items of perceptions of vaccination was calculated using logistic regression models. Demographic and job characteristics, and experiences of influenza found to be significantly associated with the influenza vaccination in the univariate models were adjusted in the final models.

Results

The overall response rate of the study was 79.5%. Table 1 showed the demographic and job characteristics, as well as influenza-related experience of the participants. Most doctors were males (64.7%), aged 25 years or younger (58.7%), resident doctors (44.6%) and living with dependents (62.7%). Half of the doctors had patient contact time <8 h/day. Among the students, the gender proportion was similar. Most of the students were in their third or fifth years of study and living with dependents (78.9%).

View this table:
Table 1

Demographic and job characteristics, and influenza experience and vaccination of the respondents

Doctors (n = 204) N (%)Medical students (n = 242) N (%)P-value
Sex
    Male132 (64.7)126 (52.1)
    Female72 (35.3)116 (47.9)
Age (years)
    ≤25262 (58.7)
    26–3595 (21.3)
    ≥3689 (20.0)
Living with dependents
    No76 (37.3)51 (21.1)
    Yes128 (62.7)191 (78.9)
Department
    Surgical related102 (50.0)
    Non-surgical related102 (50.0)
Position
    Internship17 (8.3)
    Resident91 (44.6)
    Associate consultant45 (22.1)
    Consultant37 (18.1)
Year of study
    3100 (41.3)
    444 (18.2)
    598 (40.5)
Daily patient contact time (h)
    <8103 (50.5)
    ≥891 (44.6)
    <2110 (45.5)
    ≥2124 (53.0)
URTI in the past 12 months (times)
    0–2156 (76.5)181 (75.4)0.80
    ≥348 (23.5)59 (24.6)
Sick leaves due to URTI in the past 12 months
    None154 (75.5)180 (75.3)0.97
    Any50 (24.5)59 (24.7)
Uptake of influenza vaccine in the previous year
    No123 (60.3)80 (33.1)<0.001
    Yes81 (39.7)162 (66.9)

The prevalence of having URTI three times or more and any sick leaves owing to URTI in the past 12 months were similar in doctors (23.5 and 24.5%) and medical students (24.6 and 24.7%). A significantly higher proportion of medical students (66.9%) had received the influenza vaccination in the previous year than doctors (39.7%). Moreover, students were significantly more likely than doctors to perceive that vaccination could protect themselves (77.2 vs. 58.7%) and their relatives (80.5 vs. 50.0%) from contracting influenza, benefits of influenza vaccine outweigh its side effects (94.2 vs. 79.1%), healthcare workers have the professional responsibility to receive influenza vaccine (83.4 vs. 43.5%) and vaccination can protect patients from influenza infection (85.8 vs. 52.0%) (table 2). The Cronbach's α value for the six-item scale of perceptions towards influenza vaccination was 0.78 and 0.61 in doctors and medical students, respectively.

View this table:
Table 2

Comparisons of perceptions towards influenza vaccination between doctors and medical students

Doctors (n = 204) (%)Medical students (n = 242) (%)P-value
Perceptions towards vaccination
    Influenza vaccine can protect me from influenza infection58.777.2<0.001
    Getting myself vaccinated can protect my relatives from influenza infection50.080.5<0.001
    The benefits of influenza vaccine outweigh its side effects79.194.2<0.001
    Influenza vaccine can alleviate influenza symptoms when I have influenza30.730.80.97
    Healthcare workers have professional responsibility to receive influenza vaccine43.583.4<0.001
    Getting myself vaccinated can protect my patients from influenza infection52.085.8<0.001
    Cronbach's α0.780.610.75
  • P-value for χ2 test

In table 4, Years 4 and 5 medical students had a significantly lower intention to receive influenza vaccination than those in Year 3 with the respective OR and 95% confidence interval (95% CI) of 0.28 (0.13–0.61) and 0.33 (95% CI 0.17–0.62). Moreover, having URTI three times or more in the past 12 months was significantly associated with influenza vaccination in previous year with OR (95% CI) of 1.94 (1.01–3.73) for doctors and 2.36 (1.17–4.75) for medical students (tables 3 and 4).

View this table:
Table 3

Factors associated with influenza vaccination in the previous year among doctors

N (%)Crude OR (95% CI)P-valueAdjusted OR (95% CI)P-value
Demographic and job characteristics
Sex
    Male49 (37.1)1
    Female32 (44.4)1.36 (0.76–2.43)0.31
Age (years)
    ≤3511 (42.3)1
    36–4532 (36.0)0.77 (0.31–1.87)0.56
    ≥4638 (42.7)1.02 (0.42–2.46)0.97
Living with dependents
    No31 (40.8)1
    Yes50 (39.1)0.93 (0.52–1.66)0.81
Discipline
    Surgical related34 (33.3)1
    Non-surgical related47 (46.1)1.71 (0.97–3.01)0.06
Position
    Internship8 (47.1)1
    Resident35 (38.5)0.70 (0.25–2.00)0.70
    Associate consultant20 (44.4)0.90 (0.29–2.76)0.90
    Consultant15 (40.5)0.77 (0.24–2.44)0.77
Daily patient contact time (h)
    <811 (36.7)1
    ≥865 (39.6)1.13 (0.51–2.54)0.76
URTI in the past 12 months (times)
    0–256 (35.9)1
    ≥325 (52.1)1.94 (1.01–3.73)0.04
Sick leaves due to URTI in the past 12 months
    None56 (36.4)1
    Any25 (50.0)1.75 (0.92–3.33)0.09
Perceptions towards vaccination
    Influenza vaccine can protect me from influenza infection
    No11 (13.3)11
    Yes69 (58.5)9.22 (4.43–19.2)<0.0019.20 (4.40–19.24)<0.001
Getting myself vaccinated can protect my relatives from influenza infection
    No21 (21.0)11
    Yes59 (59.0)5.41 (2.90–10.1)<0.0015.36 (2.85–10.05)<0.001
The benefits of influenza vaccine outweigh its side effects
    No4 (9.5)11
    Yes76 (47.8)8.70 (2.97–25.52)<0.0019.09 (3.07–26.95)<0.001
Influenza vaccine can alleviate influenza symptoms when I have influenza
    No47 (34.1)11
    Yes32 (52.5)2.14 (1.16–3.95)0.022.01 (1.08–3.75)0.03
Healthcare workers have professional responsibility to receive influenza vaccine
    No23 (20.4)11
    Yes56 (64.4)7.07 (3.75–13.3)<0.0017.06 (3.72–13.38)<0.001
Getting myself vaccinated can protect my patients from influenza infection
    No21 (21.9)11
    Yes58 (55.8)4.50 (2.42–8.37)<0.0014.61 (2.46–8.63)<0.001
View this table:
Table 4

Factors associated with influenza vaccination in the previous year among medical students

N (%)Crude OR (95% CI)P-valueCrude OR (95% CI)P-value
Demographic and job characteristics
Sex
    Male78 (61.9)1
    Female84 (72.4)1.62 (0.94–2.78)0.08
Living with dependents
    No33 (64.7)1
    Yes129 (67.5)1.14 (0.59–2.17)0.70
Year of study
    381 (81.0)1
    424 (54.5)0.28 (0.13–0.61)0.001
    557 (58.2)0.33 (0.17–0.62)0.001
Daily patient contact time (h)
    <2133 (66.8)1
    ≥222 (62.9)0.84 (0.40–1.77)0.65
URTI in the past 12 months (times)
    0–2113 (62.4)1
    ≥347 (79.7)2.36 (1.17–4.75)0.02
Sick leaves due to URTI in the past 12 months
    None126 (70.0)1
    Any33 (55.9)0.54 (0.30–1.00)0.05
Perceptions towards vaccination
Influenza vaccine can protect me from influenza infection
    No26 (47.3)11
    Yes135 (72.6)2.95 (1.59–5.49)0.0012.76 (1.42–5.34)0.03
Getting myself vaccinated can protect my relatives from influenza infection
    No24 (51.1)11
    Yes137 (70.6)2.30 (1.20–4.41)0.012.08 (1.05–4.14)0.04
The benefits of influenza vaccine outweigh its side effects
    No2 (14.3)11
    Yes159 (70.0)14.0 (3.06–63.4)0.00133.26 (4.06–272.6)0.001
Influenza vaccine can alleviate influenza symptoms when I have influenza
    No106 (63.1)11
    Yes54 (73.0)1.53 (0.84–2.80)0.171.21 (0.64–2.30)0.55
Healthcare workers have the professional responsibility to receive influenza vaccine
    No19 (47.5)11
    Yes142 (70.6)2.66 (1.33–5.31)0.014.01 (1.80–8.94)0.001
Getting myself vaccinated can protect my patients from influenza infection
    No15 (44.1)11
    Yes146 (70.9)3.08 (1.47–6.47)0.0032.50 (1.14–5.52)0.02

Among both doctors and medical students, uptake of influenza vaccination in the past year was significantly associated with the perceptions that ‘Influenza vaccine can protect me from influenza infection’ with the respective OR 9.20 (95% CI 4.40–19.24) and 2.76 (95% CI 1.42–5.34), ‘Getting myself vaccinated can protect my relatives from influenza infection’ with the respective OR 5.36 (95% CI 2.85–10.05) and 2.08 (95% CI 1.05–4.14), ‘The benefits of influenza vaccine outweigh its side effects' with the respective OR 9.09 (95% CI 3.07–26.95) and 33.26 (95% CI 4.06–272.6), ‘Healthcare workers have the professional responsibility to receive influenza vaccine’ with the respective OR 7.06 (95% CI 3.72–13.38) and 4.01 (95% CI 1.80–8.94), and ‘Getting myself vaccinated can protect my patients from influenza infection’ with the respective OR 4.61 (95% CI 2.46–8.63) and 2.50 (95% CI 1.14–5.52). Furthermore, uptake of influenza vaccination in the past year was significantly related to perceiving that ‘Influenza vaccine can alleviate influenza symptoms when I have influenza’ in doctors with OR 2.01 (95% CI 1.08–3.75).

Discussion

The current study documented the prevalence and associated factors of influenza vaccination among doctors and medical students before the 2009 Influenza A (H1N1) pandemic in Hong Kong. The prevalence of influenza vaccine uptake in 2008 among doctors reported in this study (39.7%) was comparable with the prevalence of willingness of HCP to accept influenza vaccine reported in another local study in 2009 (28.4%),18 but relatively lower than most of the vaccination rates reported worldwide.2428 In view of the low uptake rate in Hong Kong, establishment of a pandemic plan to prevent and control the forthcoming influenza pandemic with reference to the overseas experiences, e.g. the European Influenza Surveillance Scheme29 is urged. Moreover, innovative promotion programmes to increase influenza vaccine uptake rates in HCP should also be implemented.30 The feasibility of endorsing a policy of mandatory influenza vaccination among HCP may also be investigated.31 When compared with medical students, the influenza vaccine uptake rate was relatively lower among doctors. Medical students were also more likely to acknowledge the benefits of influenza vaccination than doctors. These may be explained by the emphasis of infectious disease control in the new medical education curriculum.

The significant associations between uptake of influenza vaccine and perceived benefits of vaccination reported in this study, such as protection of oneself, relatives and patients from contracting influenza were consistent with those factors found in other studies among HCP.25,26,3235 In line with the results from a review,36 we further found that self-protection was the strongest factor for receiving influenza vaccine among medical doctors.

There are cautions in interpreting our results. Our study was performed in a single teaching hospital, which may have a relatively higher uptake rate of influenza vaccine among HCP than other non-teaching hospitals.37,38 Moreover, the cross-sectional design also limited a further implication of the casual relation between uptakes and the perceived benefits of influenza vaccination. Furthermore, other factors related to uptake of influenza vaccine such as perceived risks of infection and availability of vaccines34 were not investigated. Nevertheless, this study is one of the few studies35 comparing the attitudes towards influenza vaccines between doctors and medical students. Moreover, the scale used to assess the perceived benefits showed a high internal validity from the Cronbach's α results. Similar questions were also used in other surveys among HCP.32,39

In the future, a longitudinal study including more HCP from different types of hospitals will help to better understand the changes of perceptions towards influenza vaccination of the HCP population in Hong Kong at different stages of the pandemics. Evidence-based education on the benefits of influenza vaccination should also be reinforced in the professional training of doctors.

Conflicts of interest: None declared.

Key points

  • The 2008 uptake rate of influenza vaccine was higher in medical students than doctors.

  • Medical students were more likely to acknowledge the benefits of influenza vaccination than doctors.

  • Perceived benefits of vaccination were associated with uptake rates of influenza vaccines in both doctors and medical students.

  • Evidence-based education on the benefits of influenza vaccination should be reinforced in the professional training of doctors.

References

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