Influenza vaccination rate among emergency department personnel: a survey of four teaching hospitals

EM Advances

CJEM 2005;7(1):17-21

Abstract

Résumé

Introduction

Influenza has caused the death of millions of people and played an important role in the history of medicine and disease. The 1918 influenza pandemic infected one-fifth of the world's population, including 25% of the US population, and it killed between 20 and 100 million people worldwide.¹ Most of its victims were young,² and medical facilities were overwhelmed.

Vaccination is the most effective strategy we have against influenza. Two recent studies^3,4 demonstrated that vaccination of health care workers reduced mortality in the elderly patients they were caring for. Similarly, a recent meta-analysis and a randomized double-blind placebo-controlled trial concluded that health care worker immunization reduces pneumonia rates, hospitalization and mortality among elderly patients.^5,6 Influenza vaccine also prevents infection in healthy adults;^7-9 therefore, province-wide vaccination programs operating currently have the potential to save lives and prevent outbreaks, but these programs have not been adequately studied.

Influenza vaccination of emergency department (ED) health care workers is important because it reduces disease transmission to patients and prevents secondary outbreaks, thereby decreasing morbidity and mortality. Low immunization rates among ED health care workers may contribute to the occurrence of influenza outbreaks. The objective of this study was to estimate the frequency of vaccination among ED health care workers and to identify factors associated with the decision to receive a vaccination.

Methods

Setting

This cross-sectional survey was conducted in the emergency departments of 4 London, Ontario teaching hospitals.

Survey development

The survey was designed by 2 of the authors (I.S. and K.D.T.) and was pre-tested on office staff, who provided feedback regarding potential bias, clarity and appropriateness of the questions. The first section solicited demographic information, including occupation, gender, age, marital status, and the presence of children in the house. The second section focused on the individual's health, documenting risk factors and comorbid conditions such as smoking, asthma, diabetes, cancer, and respiratory, blood, heart, liver or bowel disease. Respondents who reported receiving a flu shot were asked why they decided to be vaccinated, and all respondents were asked to describe their attitude toward influenza vaccination, including feelings about future vaccination programs, perceived effectiveness of the vaccine, and perceived risks to patients and health care workers who are exposed to unvaccinated people.

Sampling

A questionnaire and explanatory letter were distributed to all ED staff who are exposed to patients during their work hours, including medical personnel (physicians, residents, respiratory therapists and nurses) and allied health care workers (clerical staff, personal and technical support attendants, orderlies, clerks and office staff). The 28-item questionnaires were placed into the mailboxes of the staff, and a survey return box was located nearby for completed questionnaires. All questionnaires were numbered, and these numbers corresponded to names on staff lists from each participating emergency department. To maintain respondent confidentiality, an independent assistant unrelated to the study collected the surveys and arranged for re-mailing to non-responders.

Surveys were distributed between March and April 2000, with an initial response deadline of June 2000. After the initial deadline, staff who did not return a survey were contacted by internal mail with another copy of the survey, again through the use of hospital mailboxes. A follow-up letter reiterated the study purpose and urged the respondent to complete and return his or her survey.

Data analysis

Univariate logistic regression analysis was performed to determine the associations between respondent characteristics and vaccination. Predictor variables that were significantly associated with vaccination (p < 0.10) were retained in multivariate models using forward and backward stepwise multivariable logistic regression and the likelihood ratio method. The probability of a type I error in the final models was chosen to be 0.05 (two-tailed). Goodness of fit for the logistic-regression models was examined by use of the Hosmer-Lemeshow goodness-of-fit test. Analyses were performed using SPSS (version 10.0, SPSS Inc., Chicago, Ill.) and this study was conducted in accordance with the survey guidelines of the local institutional research ethics review board.

Results

Of 426 questionnaires distributed, 343 (80.5%) were returned. Table 1 summarizes characteristics and influenza vaccination rates for the survey respondents. The mean age was 38.5 years (standard deviation = 8.3), 74.3% of respondents were female and 86.6% were non-smokers. Overall, 34 were physicians or residents, 139 were nurses, 111 were respiratory therapists, and 59 were allied health care workers (i.e., non-clinical staff, including clerical staff, personal and technical support attendants, orderlies, clerks and office staff).

Overall, 37.0% (95% confidence interval [CI], 31.9%-42.4%) reported that they had been vaccinated against influenza. Vaccination rates reported by respiratory therapists, emergency physicians and residents, nurses and other allied health care workers were 45.9%, 35.3%, 34.5% and 27.1% respectively (p = 0.083) (Fig. 1). Multivariate logistic regression analysis revealed that age ≥41 (odds ration [OR] = 1.9; 95% CI, 1.1-3.4; p = 0.04) and a chronic medical condition (OR = 1.6; 95% CI, 1.0-2.5; p = 0.02) were positively associated with influenza vaccination. The Hosmer-Lemeshow goodness-of-fit statistic showed an adequate fit for the model (chi-squared = 0.37, degree of freedom = 8, p = 0.831). Of those who received influenza vaccine in the 1999-2000 season, 65.9% had also been vaccinated in previous years. Amongst those who did not receive vaccine in 1999-2000, 16.7% had been vaccinated in the past. Length of employment, gender, smoking history and marital status were not significantly correlated with the likelihood of being vaccinated.

Fig. 1. Influenza vaccination rates by occupation of respondent

Of those vaccinated, 89.5% were immunized at the hospital and 7.3% were immunized by their family doctor. Although 28.3% of respondents believe that vaccine adverse effects are common, most (76.8%) of those vaccinated reported no adverse effects. Half of respondents believe that influenza immunization is effective, 17.9% thought it is ineffective and 31.3% were unsure. Overall 28.3% felt that they were not well informed about the vaccine or its effectiveness. Most health care workers (58.3%) believe they are at risk of contracting influenza from patients, whereas only 26.8% felt that patients are at risk of contracting influenza from health care workers. When asked about the future, 47.3% of respondents planned to get the flu shot the following year. Approximately half of the respondents (51.6%) would support a vaccination program at work to help improve rates, but only 24.4% supported a mandatory program.

Discussion

Although vaccination of health care workers has been shown to improve patient outcomes, only 37% of ED health care workers in this study had been vaccinated against influenza. The study data show that older health care workers and those with chronic medical conditions were more likely to accept vaccination, and that other variables such as smoking, marital status, length of employment and having children in the house were not related to vaccination. Health care workers believed that the risk of disease transmission from patients to health care workers is greater than the risk of transmission from health care workers to patients.

A recent study found that previous vaccination, a belief that prevention is important, and belief that vaccination is effective are associated with higher health care worker vaccination rates.¹⁰ Other factors associated with vaccination are older age, female gender, marriage, longer employment, higher income, minimal absenteeism (nurse clinicians), employment duration (professional support staff) and older age (non-professional staff).¹¹ Thomas and colleagues showed that educational interventions are helpful and that health care worker vaccination rates increased from 8% to 46% when an educational intervention was followed by a vaccination fair.¹²

A multicentre study of health care workers showed that between 28%-59% of influenza cases are subclinical, that 23.2% of health care workers had a rise in influenza titres, but that only 8% took sick leave.¹³ This suggests that health care workers tend to work when they are sick, and that many may not know they are harbouring virus. This increases the likelihood of spread to susceptible individuals, especially those who have not been vaccinated.

Although health care worker vaccination reduces patient mortality in long-term care facilities, the same has not been clearly shown in the ED setting, and these data would help clarify the cost-effectiveness of future vaccination programs directed specifically at emergency department personnel.

Limitations

An important limitation of this study is the fact that all data were self-reported. The accuracy of the responses therefore depended on each respondent's recollection of being vaccinated and the willingness to admit they had not been vaccinated. The number of physicians surveyed was small, limiting the precision of estimates in this group, and external validity is uncertain, although these data reflect all hospitals in the city of London, Ontario. Finally, since the data is 4 years old, it is possible that health care workers' attitudes may have changed as the result of recent infectious disease outbreaks.

Conclusions

Future research should assess the effectiveness of educational and other interventions on improving health care worker vaccination rates, and might focus on younger health care workers with no chronic medical conditions, who may perceive themselves as being less susceptible to influenza.

In this study, only 37% of ED health care workers were immunized, with chronic illness and older age being the only two significant correlates. Strategies to increase health care worker vaccination rates should be developed.

References

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