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. 2016 Sep 7;4(3):E479–E488. doi: 10.9778/cmajo.20160018

Influenza immunization among Canadian health care personnel: a cross-sectional study

Sarah A Buchan 1, Jeffrey C Kwong 1
PMCID: PMC5047845  PMID: 27730112

Abstract

Background:

Influenza immunization coverage among Canadian health care personnel remains below national targets. Targeting this group is of particular importance given their elevated risk of influenza infection, role in transmission and influence on patients' immunization status. We examined influenza immunization coverage in health care personnel in Canada, reasons for not being immunized and the impact of "vaccinate-or-mask" influenza prevention policies.

Methods:

In this national cross-sectional study, we pooled data from the 2007 to 2014 cycles of the Canadian Community Health Survey and restricted it to respondents who reported a health care occupation. Using bootstrapped survey weights, we examined immunization coverage by occupation and by presence of vaccinate-or-mask policies, and reasons for not being immunized. We used modified Poisson regression to estimate the prevalence ratio (PR) of influenza immunization for health care occupations compared with the general working population.

Results:

For all survey cycles combined, 50% of 18 446 health care personnel reported receiving seasonal influenza immunization during the previous 12 months, although this varied by occupation type (range 4%-72%). Compared with the general working population, family physicians and general practitioners were most likely to be immunized (PR 3.15, 95% confidence interval [CI] 2.76-3.59), whereas chiropractors, midwives and practitioners of natural healing were least likely (PR 0.17, 95% CI 0.10-0.30). Among those who were not immunized, the most frequently cited reason was the belief that influenza immunization is unnecessary. Introduction of vaccinate-or-mask policies was associated with increased influenza immunization among health care personnel.

Interpretation:

Health care personnel are more likely to be immunized against influenza than the general working population, but coverage remains suboptimal overall, and we observed wide variation by occupation type. More efforts are needed to target specific health care occupations with low immunization coverage.

Seasonal influenza causes substantial morbidity and mortality for high-risk groups such as older adults, young children and those with underlying medical conditions.1-3 These high-risk groups have frequent contact with the health care system and health care personnel.4,5 Health care personnel are at higher risk of influenza infection compared with people who work in non-health care settings,6 and may be a source for influenza transmission in health care settings.7-9 Previous studies have suggested that there is an inverse relationship between health care personnel immunization and nosocomial infections.10 Furthermore, immunization beliefs and status of health care providers influence patient decisions about immunization.11

Canada's National Advisory Committee on Immunization (Public Health Agency of Canada) recommends annual seasonal influenza immunization for health care personnel as part of the standard of care for protecting patients,12 with a national target of 80% coverage for health care personnel who have close contact with patients.13 The term "health care personnel" includes many diverse occupations, and studies estimating influenza immunization coverage among health care personnel have not commonly reported about specific occupations.14,15 Some studies in the United States have used large national surveys, but those results may not be generalizable to the Canadian context.16,17

Numerous organizations in the US have introduced mandatory influenza immunization policies for health care personnel, with subsequent notable increases in coverage.18,19 In recent years, several Canadian jurisdictions have implemented health care personnel "vaccinate-or-mask" influenza prevention policies, which require hospital-based health care personnel to either receive seasonal influenza immunization or wear a surgical mask during periods of influenza activity. Such policies were introduced in British Columbia and 1 of New Brunswick's 2 regional health networks (Horizon Health Network) in 2012-13, Saskatchewan in 2014-15 and selected hospitals across Ontario from 2012-13 to 2014-15.20,21

Our objectives for this study were to examine influenza immunization and the reasons for not being immunized, by health care occupation group and specific occupation. Additionally, we aimed to determine the impact of the introduction of vaccinate-or-mask influenza prevention policies on health care personnel influenza immunization coverage.

Methods

Study population

We used nationally representative data from the 2007 to 2014 cycles of the Canadian Community Health Survey (survey).22 Conducted annually by Statistics Canada since 2007 through telephone and in-person interviews, this cross-sectional survey contains questions related to health status, health care utilization and health determinants.22 Using a multistage stratified cluster design, each cycle includes a sample of about 65 000 respondents aged 12 years and older. The survey excludes persons living on Aboriginal reserves, full-time members of the Canadian military, institutionalized persons and 2 remote health regions in Quebec (with all of these exclusions representing < 3% of the population).22

We restricted our study to respondents 15-75 years of age who reported having a job during the week before being asked to respond to the survey. We assessed influenza immunization among those working in health care occupations. Response rates ranged from 65.6% to 77.6% across the survey cycles.23

Sources of data

We defined the dependent variable as self-reported influenza immunization within the past 12 months, determined through responses to the questions "Have you ever had a (seasonal) flu shot?" and "When did you have your last (seasonal) flu shot?". Respondents who reported receipt of their last flu shot during the preceding 12 months were considered immunized. These respondents were also asked "In which month did you have your last flu shot?." Those whose response matched the month of the survey date were then asked "Was that this year or last year?". We considered respondents who reported receipt of influenza vaccine during the same month as the survey date but in the preceding year as not immunized. Respondents who reported not receiving influenza immunization during the last 12 months were asked a series of questions related to their reasons for not being immunized.

To identify health care personnel, we used the National Occupation Classification for Statistics, established by Human Resources and Social Development Canada in partnership with Statistics Canada.24 Eligible respondents were asked about their specific occupation, which was coded and organized into a predefined hierarchy of 10 broad categories (1 of which comprises all health occupations) that are subdivided into health occupation groups and specific health occupations. We adapted this classification structure, making changes based on sample size and cohesiveness of the group (e.g., we combined chiropractors and practitioners of natural healing with midwives because both groups were too small on their own to produce sufficiently stable estimates to be reported and their coverage levels were similar).

We defined presence of a vaccinate-or-mask influenza prevention policy based on jurisdiction and influenza season (i.e., year). We considered British Columbia and the Horizon Health Network in New Brunswick to have this policy for 2012-13 and 2013-14. We included the survey health region that exclusively comprises Horizon Health Network and excluded Moncton because this city is split between Horizon Health Network and Vitalité Health Network. We also excluded Ontario from this analysis, because we could not align hospitals that introduced these policies with survey health regions.

To determine the presence of chronic medical conditions, respondents were asked whether they had been diagnosed by a health professional with asthma, chronic obstructive pulmonary disease, heart disease, stroke, diabetes or cancer, conditions for which influenza vaccines are recommended.12 The definitions for education, household income, smoking status, body mass index, immigration status, marital status, rural residence, self-reported health, and having a regular doctor were described previously.25,26 We combined the 3 territories because of their small sample sizes.

Statistical analysis

We pooled individual-level responses from all survey cycles, with the final data set considered a sample from an average population observed over time.27 Using cross-tabulations, we estimated the overall proportion of health care personnel who reported seasonal influenza immunization during the previous year by various sociodemographic characteristics (i.e., age, sex, education, income and location), as well as by province and season. We also examined influenza immunization coverage by health occupation group and by specific occupation, looking at both whether the respondent had been immunized during the last 12 months and whether they had ever been immunized. Cross-tabulations were also used to examine the reasons provided by respondents who were not immunized and to compare jurisdictions that had introduced vaccinate-or-mask policies for health care personnel with those that had not.

We chose modified Poisson regression over logistic regression to estimate the prevalence of influenza immunization in specific health care occupations compared with other occupations outside of health care. Logistic regression analyses would have overestimated this relationship because of the high frequency of the outcome.28 Using modified Poisson regression also allows for the prevalence ratios to be interpreted as a relative risk.29 We used the Hosmer-Lemeshow goodness-of-fit test forward model-building strategy to develop our multivariable model.30 We performed univariable regression analysis for all variables that were identified a priori to be of potential importance, and they were entered into the model based on their effect size. Variables that had a significant impact on the prevalence ratio for vaccination of health care personnel were kept in the model, with a verification step at the end to ensure no important variables were missed. Given its importance on influenza immunization uptake, age was forced into the model. After applying this model-building strategy, only age and sex remained in the model.

We used sampling weights to account for the unequal probability of selection in the sample and bootstrap survey weights to calculate variance estimates. We used normalized weights for the multivariable regression analysis. All tests were 2-sided and used a significance level of p < 0.05. We used SAS statistical software (version 9.4, SAS Institute Inc.) for all analyses.

Ethics approval

This study was approved by the Ethics Review Board of Public Health Ontario.

Results

Our total sample included 249 607 respondents (weighted n = 16 524 003) aged 15-75 years who reported having a job during the previous week; of these, 18 446 (weighted n = 1 130 731) were classified as having a health care occupation. Most health care personnel were female, had attained high levels of education and had high household income (Table 1).

Table 1: Selected demographic characteristics of the study population. Table 1: Selected demographic characteristics of the study population.

Characteristic n, unweighted¶ n, weighted (%) Influenza immunization,
% (95% CI)
All health care personnel 18 446 1 130 731 (100) 50 (49-51)
Sex
    Female 15 645 914 069 (80.8) 50 (49-51)
    Male 2800 216 662 (19.2) 51 (48-54)
Age, yr
    15-29 3485 232 521 (20.6) 45 (43-48)
    30-49 8280 560 815 (49.6) 48 (46-50)
    50-64 6080 312 206 (27.6) 56 (53-58)
    65-75 600 25 188 (2.2) 70 (65-76)
Education
    Some secondary 365 16 271 (1.4) 39 (31-48)
    Secondary 855 53 360 (4.7) 47 (40-53)
    Some postsecondary 485 32 473 (2.9) 38 (31-45)
    Postsecondary 16 660 1 024 262 (90.6) 51 (50-52)
    Not stated 80 4365 (0.4) 56 (39-72)
Household income
    Lowest* 335 18 363 (1.6) 42 (33-51)
    Lower middle† 1345 80 223 (7.1) 46 (40-52)
    Upper middle‡ 4845 274 579 (24.3) 45 (43-48)
    Highest § 11 035 696 155 (61.6) 53 (51-54)
    Not stated/missing 890 61 411 (5.4) 51 (45-57)
Location
    Urban 13 735 935 286 (82.7) 51 (49-52)
    Rural 4710 195 445 (17.3) 48 (46-51)
Health occupation group
    Diagnosing and treating professionals 1405 110 499 (9.8) 58 (53-62)
    Chiropractors and midwives 250 18 852 (1.7) 4 (1-7)**
    Allied health professionals 1580 99 048 (8.8) 48 (44-53)
    Nurses 6665 387 740 (34.3) 57 (55-60)
    Medical technologists and technicians 1545 99 112 (8.8) 43 (39-47)
    Dental technicians 450 31 248 (2.8) 23 (17-29)
    Other technical occupations in health care 1020 58 719 (5.2) 27 (23-32)
    Assisting occupations in support of health services 5535 325 513 (28.8) 51 (49-53)
Province/territory
    Newfoundland and Labrador 585 19 891 (1.8) 37 (32-43)
    Prince Edward Island 315 5 575 (0.5) 55 (47-62)
    Nova Scotia 840 39 513 (3.5) 62 (58-67)
    New Brunswick 785 26 715 (2.4) 50 (45-54)
    Quebec 3405 268 993 (23.8) 40 (37-43)
    Ontario 5810 396 944 (35.1) 52 (50-54)
    Manitoba 1325 49 681 (4.4) 41 (36-46)
    Saskatchewan 1250 38 231 (3.4) 59 (55-63)
    Alberta 1650 125 895 (11.1) 56 (52-60)
    British Columbia 2095 157 119 (13.9) 57 (53-60)
    Territories combined 380 2 174 (0.2) 58 (51-64)
Influenza season
    2006-07 1860 99 821 (8.8) 52 (48-55)
    2007-08 2455 139 235 (12.3) 51 (48-55)
    2008-09 2300 144 191 (12.8) 53 (50-57)
    2009-10 2320 143 398 (12.7) 43 (40-47)
    2010-11 2345 148 604 (13.1) 51 (47-54)
    2011-12 2400 141 030 (12.5) 47 (43-50)
    2012-13 2415 155 749 (13.8) 49 (46-53)
    2013-14 2345 158 702 (14.0) 55 (51-58)
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Note: CI = confidence interval.

*Based on the following categories: 1-2 people in household, household income < $15 000; 3-4 people in household, household income < $20 000; > 5 people in household, household income < $30 000.

†Based on the following categories: 1-2 people in household, household income $15 000-$29 999; 3-4 people in household, household income $20 000-$39 999; > 5 people in household, household income $30 000-$59 999.

‡Based on the following categories: 1-2 people in household, household income $30 000-$59 999; 3-4 people in household, household income $40 000-$79999; > 5 people in household, household income $60 000-$79 999.

§Based on the following categories: 1-2 people in household, household income > $60 000; > 3 people in household, household income > $80 000.

¶As per Statistics Canada confidentiality rules, unweighted n values have been rounded to the nearest 5.

**Use with caution (coefficient of variation 16.6%-33.3%).

Influenza immunization by occupation

Overall, 50% (95% confidence interval [CI] 49%-51%) of health care personnel reported receiving seasonal influenza immunization during the past 12 months, and 77% (95% CI 76%-79%) reported ever receiving immunization, compared with 21% (95% CI 20%-21%) and 51% (95% CI 50%-51%), respectively, in the general working population. Immunization coverage in health care personnel varied between provinces (range 37%-62%) and influenza seasons (range 43%-55%).

We observed a wide range of coverage by health occupation group (range 4%-58%) and by specific occupation (range 4%-72%) (Table 2). The extent of variability was not consistent across health occupation groups: for example, coverage levels were similar between the 3 types of nurses (53% for head nurses and supervisors, 58% for registered nurses and 59% for licensed practical nurses) but ranged from 36% to 61% among allied health professionals. Family physicians and general practitioners had the highest reported occupation-specific coverage (72%, 95% CI 65%-79%), whereas chiropractors, midwives and practitioners of natural healing had the lowest (4%, 95%CI 1%-7%).

Table 2: Influenza immunization among health care personnel, by occupation.

Occupation n, unweighted* n = 18 446 n, weighted
n = 1 130 731		 Flu shot in last 12 mo,
% (95% CI)		 Ever had flu shot, 
% (95% CI)
Diagnosing and treating professional 1405 110 499 58 (53-62) 80 (76-84)
    Specialist physician 380 31 401 59 (51-67) 85 (80-90)
    Family physician or general practitioner 565 46 902 72 (65-79) 86 (80-93)
    Dentist 205 17 542 44 (31-57) 75 (64-85)
    Optometrist 85 4 323 32 (17-47)† 75 (64-87)
    Veterinarian 170 10 331 20 (11-29)† 46 (32-59)
Chiropractor, midwife or practitioner of natural healing 250 18 852 4 (1-7)† 26 (16-35)† 
Allied health professional 1580 99 048 48 (44-53) 79 (75-82)
    Pharmacist 450 28 134 50 (43-58) 79 (71-86)
    Dietitian or nutritionist 165 8 338 61 (50-72) 84 (75-92)
    Audiologist or speech language pathologist 195 10 857 36 (26-47) 78 (68-88)
    Physiotherapist 405 26 938 44 (36-51) 73 (66-80)
    Occupational therapist 265 18 399 51 (39-62) 83 (76-89)
    Other professional occupation in therapy and assessment 95 6 382 55 (40-70) 86 (77-95)
Nurse 6665 387 740 57 (55-60) 84 (83-86)
    Head nurse or supervisor 485 29 528 53 (45-62) 76 (67-85)
    Registered nurse 4970 295 545 58 (55-60) 85 (83-87)
    Licensed practical nurse 1210 62 667 59 (54-64) 84 (81-88)
Medical technologist or technician 1545 99 112 43 (39-47) 71 (67-75)
    Medical laboratory technologist or pathologist's assistant 420 26 556 54 (46-62) 76 (68-84)
    Medical laboratory technician 295 20 207 48 (39-57) 72 (63-81)
    Respiratory therapist, clinical perfusionist or cardiopulmonary technologist 125 9 015 47 (34-60) 77 (65-90)
    Medical radiation technologist 335 19 385 44 (35-54) 72 (63-82)
    Medical sonographer, cardiology technologist, electroencephalographic or other diagnostic technologist, or other medical technologist or technician 130 8 908 35 (23-47)† 67 (54-79)
    Veterinary technician 235 15 041 18 (9-27)† 55 (46-65)
Dental technician 450 31 248 23 (17-29) 58 (51-65)
    Denturist or dental technologist, technician or laboratory bench worker 90 7 680 33 (20-47)† 56 (41-71)
    Dental hygienist or dental therapist 360 23 568 19 (13-26) 59 (51-67)
Other technical occupation in health care 1020 58 719 27 (23-32) 60 (55-65)
    Optician 115 7 928 15 (6-25)† 39 (25-53)†
    Ambulance attendant or other paramedic occupation 510 25 678 46 (38-53) 83 (78-88)
    Other 390 25 113 13 (8-17)† 44 (36-51)
Assisting occupation in support of health services 5535 325 513 51 (49-53) 78 76-80
    Dental assistant 370 24 747 32 (24-39) 66 (59-74)
    Nurse aide, orderly and patient services associates 4140 237 232 56 (53-59) 82 (80-84)
    Other 1030 63 534 38 (33-43) 69 (64-73)
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Note: CI = confidence interval.

*As per Statistics Canada confidentiality rules, unweighted n values have been rounded to the nearest 5.

†Use with caution (coefficient of variation 16.6%-33.3%).

In the multivariable analysis, healthcare personnel overall had significantly higher influenza immunization coverage than the general working population both before (prevalence ratio [PR] 2.43, 95% CI 2.36-2.51) and after adjustment (PR 2.26, 95% CI 2.19-2.34). This was also true for all health occupation groups except dental technicians and chiropractors, midwives and practitioners of natural healing (Figure 1). Higher coverage was not observed for certain specific occupations (i.e., optometrists, veterinarians, veterinary technicians, dental hygienists and dental therapists, opticians, and those belonging to the other category of technical occupations in health care). Family physicians and general practitioners were most likely to receive influenza immunization (PR 3.15, 95% CI 2.76-3.59), followed by licensed practical nurses (PR 2.69, 95% CI 2.46-2.95), dieticians and nutritionists (PR 2.67, 95% CI 2.23-3.20) and specialist physicians (PR 2.63, 95% CI 2.29-3.02). In contrast, chiropractors, midwives and practitioners of natural healing were the least likely to receive influenza immunization (PR 0.17, 95% CI 0.10-0.30).

Figure 1.

Figure 1

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Prevalence ratios for influenza immunization (compared to the general working population) adjusted for age and sex, by health care occupation. Note: CI = confidence interval.

Reasons for not receiving influenza immunization

Among those not immunized (n = 8354; weighted n = 537 674), the most frequently cited reason, consistent across all occupations, was believing influenza immunization to be unnecessary (all health care personnel = 67%) (Table 3). Family physicians and general practitioners had the lowest percentage of citing this reason (52%) among respondents, whereas chiropractors, midwives and practitioners of natural healing had the highest percentage (92%). The other most frequently cited reasons included "not getting around to it" (14%), "having a previous bad reaction" (10%), and fear (5%). This order was consistent across health occupation groups, except for nurses, for whom having a previous bad reaction was the second most frequently cited reason.

Table 3: Nonimmunization for influenza among health care personnel, by occupation.

Occupation n, unweighted*
n = 8534		 n, weighted
n = 537 674		 Feels flu shot is unnecessary,
% (95% CI)
Diagnosing and treating professional 585 44 499 63 (56-70)
    Specialist physician 145 11 275 57 (45-70)
    Family physician or general practitioner 125 12 346 52 (35-68)
    Dentist 125 9679 72 (59-84)
    Optometrist 60 2924 54 (36-71)†
    Veterinarian 130 8275 81 (70-92)
Chiropractor, midwife or practitioner of natural healing 225 18 101 92 (87-97)
Allied health professional 760 48 576 66 (61-71)
    Pharmacist 185 12 443 63 (52-74)
    Dietitian or nutritionist 65 3186 87 (77-97)
    Audiologist or speech language pathologist 110 6662 57 (43-71)
    Physiotherapist 220 14 642 73 (65-82)
    Occupational therapist 130 8989 61 (49-74)
    Other professional occupation in therapy and assessment 45 2654 54 (32-77)†
Nurse 2610 153 313 63 (59-66)
    Head nurse or supervisor 185 12 504 64 (51-77)
    Registered nurse 1915 116 720 63 (59-66)
    Licensed practical nurse 510 24 089 62 (55-69)
Medical technologist or technician 815 55 091 76 (72-80)
    Medical laboratory technologist or pathologist's assistant 180 11 711 77 (68-86)
    Medical laboratory technician 155 10 117 72 (62-82)
    Respiratory therapist, clinical perfusionist or cardiopulmonary technologist 60 4635 79 (67-90)
    Medical radiation technologist 150 10 736 79 (70-88)
    Medical sonographer, cardiology technologist, electroencephalographic or other diagnostic technologist, or other medical technologist or technician 70 5651 75 (62-88)
    Veterinary technician 195 12241 75 (64-86)
Dental technician 325 23 189 63 (54-72)
    Denturist or dental technologist, technician or laboratory bench worker 60 4972 62 (43-81)†
    Dental hygienist or dental therapist 265 18 217 63 (53-73)
Other technical occupation in health care 670 41 155 76 (71-81)
    Optician 90 6438 78 (65-90)
    Ambulance attendant or other paramedic occupation 260 13 318 69 (59-78)
    Other 320 21 399 80 (73-87)
Assisting occupation in support of health services 2540 153 750 66 (63-69)
    Dental assistant 255 16 714 71 (62-81)
    Nurse aide, orderly and patient services associates 1685 98 569 65 (61-69)
    Other 600 38 467 67 (61-74)
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Note: CI = confidence interval.

*As per Statistics Canada confidentiality rules, unweighted n values have been rounded to the nearest 5.

†Use with caution (coefficient of variation 16.6%-33.3%).

Impact of vaccinate-or-mask policies on influenza immunization among health care personnel

In areas where vaccinate-or-mask policies were implemented, influenza immunization among health care personnel increased from 52% (95% CI 49%-56%) before the 2012-2013 influenza season to 68% (95% CI 62%-74%) after 2012-2013 compared with a change from 47% (95% CI 44%-49%) to 46% (95% CI 43%-50%) in areas that did not implement such policies (Figure 2).

Figure 2.

Figure 2

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Influenza immunization, by presence of vaccinate-or-mask influenza prevention policies for health care personnel (excluding Moncton Health Region and the province of Ontario).

Interpretation

Main findings

Immunization coverage among Canadian health care personnel remains below the national target, with large variations by specific occupation. Family physicians and general practitioners are most likely to receive influenza immunization, whereas chiropractors, midwives and practitioners of natural healing are least likely.

Comparison with other studies

Past studies of influenza immunizaton among health care personnel using Canadian Community Health Survey data considered health care personnel as a single entity and were based on industry classification rather than occupation type. Johansen and colleagues reported that 46% of people in health care industries in 2003 received their influenza vaccine.14 Gilmour and Hofmann examined uptake of H1N1 influenza vaccine in 2010 and found that health care workers had significantly higher uptake than non-health care workers (65.9% v. 34.8%).31 Some organization-specific studies have provided data on a limited number of subgroups but have focussed more on understanding attitudes and motivators of workers within these organizations.32,33 Saluja and colleagues noted variation in uptake among those who worked in emergency departments; however, they only reported on 4 health care worker groups.34

In the US, opt-in surveys of health care personnel have been conducted annually, with the most recent data reporting that 75.2% were immunized in 2013-14.35 This was highest for physicians (92.2%) and for health care professionals whose employers required them to be immunized (97.8%).35 The finding that physicians have the highest influenza immunization coverage among health care personnel is echoed in our study, as well as other national surveys.36 Additionally, our finding that influenza immunization coverage among health care personnel overall is suboptimal is also consistent with other research.36-40

We found that chiropractors, midwives and other practitioners of natural healing had the lowest uptake of influenza immunization. A previous survey of Ontario midwives also found that midwives were less likely to receive influenza immunization than other health care personnel.41 The use of alternative practitioners has become increasingly common in Canada.42,43 Like other health care personnel, they may have patients who are considered to be at high risk of serious complications from influenza infection, and, by not being immunized each year, they may be placing their patients at risk of serious morbidity and mortality from influenza infection. Given the burden of influenza during pregnancy and the effectiveness of influenza immunization in preventing influenza infection in both pregnant woman and their infants,44,45 and acknowledging the increasingly important role of midwives in pregnancy care, efforts are needed to promote influenza immunization within this group in particular.

Although some recent studies attempted to identify effective measures for promoting immunization of health care personnel in hospitals or primary care settings, results varied.32,46-50 Some research highlighted the beneficial impacts of enhanced education and the use of "champions" to increase coverage,49,50 whereas others suggested the need for a larger paradigm shift to a culture of vaccine promotion.32,48,51 Despite this research at the organizational level, further studies focused on individual health care occupations, such as those identified here, and their specific concerns are needed; targeted strategies can then help bolster immunization coverage within the respective group.52,53

Limitations

Our outcome measure, influenza immunization during the past 12 months, is self-reported and may be subject to reporting bias. Although past studies showed this outcome to be a valid measure of influenza immunization status,54,55 social desirability bias may have had a greater impact on health care personnel compared with the general population. Our study may also be limited in its ability to capture the full range of people who have patient contact but might not be classified as having a health care occupation. For example, we may have missed important groups, such as administrative or support staff, who are employed in health care settings and have regular contact with patients. Additionally, the location of employment was unavailable; the importance of health care personnel immunization is expected to vary considerably by patient population and setting (e.g., intensive care unit versus community pharmacy or optical store). For the analysis examining the impact of vaccinate-or-mask policies, we may have misclassified health care personnel who work in 1 health authority in New Brunswick and live in the other, but this number was expected to be small. Furthermore, although New Brunswick and British Columbia implemented these policies for entire jurisdictions, several individual organizations also implemented policies for their health care personnel, and we were unable to assess the impact of these organization-level policies with the available data. Finally, we were not able to look at trends over time for specific occupations because of sample size limitations.

Conclusion

Given the breadth of occupations represented by health care personnel, influenza immunization coverage should be measured using more specific categories. Our results suggest the need for targeted strategies to promote influenza immunization in groups with very low uptake and/or for whom provider protection is of critical importance to the patient population. Members of occupations with high coverage could serve as champions of influenza immunization for other health care personnel and patients.

Supplemental information

For reviewer comments and the original submission of this manuscript, please see www.cmajopen.ca/content/4/3/E479/suppl/DC1

Supplementary Material

Online Appendices
supp_4_3_E479__index.html (890B, html)

Acknowledgements

Sarah Buchan was supported by a Canadian Immunization Research Network Trainee Award. Jeffrey Kwong was supported by a New Investigator Award from the Canadian Institutes of Health Research and a Clinician Scientist Award from the Department of Family and Community Medicine, University of Toronto. The authors thank David Haans and Joanna Jacob (Statistics Canada Research Data Centre, University of Toronto) for their support and guidance.

Footnotes

ICES Disclaimer: This study was supported by the Institute for Clinical Evaluative Sciences, (ICES) which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). The opinions, results and conclusions reported in this article are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario MOHLTC is intended or should be inferred.

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Supplementary Materials

Online Appendices
supp_4_3_E479__index.html (890B, html)
supp_4.3.E479_Reviewer_comments_2016-0018.pdf (27.2KB, pdf)
supp_4.3.E479_2016-0018_Original_submission.pdf (290.5KB, pdf)
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