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. 2021 Nov 19;16(11):e0260213. doi: 10.1371/journal.pone.0260213

Influenza vaccination coverage among emergency department personnel is associated with perception of vaccination and side effects, vaccination availability on site and the COVID-19 pandemic

Anna-Maria Stöckeler 1, Philipp Schuster 2, Markus Zimmermann 3, Frank Hanses 1,3,*
Editor: Megan Lindley4
PMCID: PMC8604289  PMID: 34797861

Abstract

Introduction

Influenza is a major concern in hospitals, including the emergency department (ED), mainly because of a high risk for ED personnel to acquire and transmit the disease. Although influenza vaccination is recommended for health care workers, vaccination coverage is low.

Methods

This survey was conducted in the 2016/2017 and 2020/2021 influenza seasons. Questionnaires were sent to ED personnel in 12 hospitals in Bavaria, South-Eastern Germany. The response rates were 62% and 38% in 2016/2017 and 2020/2021, respectively. Data were compared between the two seasons as well as between vaccinated and not vaccinated respondents in 2020/2021.

Results

Significantly more ED personnel reported having been vaccinated in the 2020/2021 season. Factors associated with vaccination coverage (or the intention to get vaccinated) were profession (physician / medical student), having been vaccinated at least twice, the availability of an influenza vaccination on site (in the ED) as well as the COVID-19 pandemic. Additionally, significant differences in the assessment and evaluation of influenza, its vaccination side effects and ethical aspects were found between vaccinated and not vaccinated ED personnel in 2020/2021. Unvaccinated respondents estimated higher frequencies of almost all potential vaccination side effects, were less likely to accept lay-offs if employees would not come to work during an influenza pandemic and more likely to agree that work attendance should be an employee´s decision. Vaccinated participants instead, rather agreed that vaccination should be mandatory and were less likely to consider job changes in case of a mandatory vaccination policy.

Conclusion

The COVID-19 pandemic might have contributed to a higher influenza vaccination rate among ED workers. Vaccination on site and interventions targeting the perception of influenza vaccination and its side effects may be most promising to increase the vaccination coverage among ED personnel.

Introduction

Seasonal influenza is an acute contagious respiratory disease caused by type A or B influenza viruses [1]. The disease is associated with significant morbidity causing a high number of cases, hospitalizations and deaths annually [2]. Each year, approximately 4–16 million people contract influenza in Germany, of which up to 20000 die [3]. Vaccination represents a cost-effective way to reduce influenza-like illnesses, sick leave, societal cost [4, 5] and is deemed especially important for persons at high risk of contracting the virus or becoming severely ill [6–8]. Health care workers are frequently exposed to contagious agents leading to a risk of infection and transmission of diseases [9]. In particular, ED staff are at the front line caring for a large number of patients compared with other departments, including both vulnerable patients and individuals with acute respiratory infections like influenza. Not least due to the close proximity and an extended duration of patient contacts, the ED poses a great risk for spreading nosocomial infections [9–11]. Besides vaccination of persons with increased risk of complication from influenza disease, WHO, CDC as well as the German standing vaccination committee (STIKO) recommend that health care workers among others get vaccinated annually against influenza to protect employees, decrease work absenteeism and reduce virus spreading and transmission within the hospital [7, 12–14]. However, vaccination rates among health care workers in general and ED personnel in particular fall short of expectations and implementation strategies have led to mixed success so far. According to a survey by the Robert Koch Institute (the institute for Public Health in Germany–RKI) conducted in 52 hospitals including 5808 employees, only 39,5% of health care workers in Germany were vaccinated in the 2017/2018 season [12, 15]. Previous research into the reasons why health care workers choose not to get vaccinated has highlighted concerns about its effectiveness or lack of knowledge about influenza vaccination [11, 16, 17]. The exposure to severe respiratory infectious diseases during the current COVID-19 pandemic may change the perceptions and positively affect the influenza vaccination rate [16]. We hypothesize that higher uptake of influenza vaccination can be found compared to previous years among health care workers, especially those working in the ED and thus are frequently exposed to COVID-19 patients. We therefore conducted a survey among ED personnel from different hospitals in Bavaria, South-Eastern Germany, on influenza and influenza vaccination and compared influenza vaccination attitude/readiness from a “before COVID-19” season (2016/2017) to a “during COVID-19” season (2020/2021).

Materials and methods

Our impression was that the vaccination rate in emergency departments leaves room for improvement. We therefore conducted a baseline survey between March 2, 2017 and July 3, 2017 (influenza season 2016/2017) among ED personnel in hospitals in Bavaria, South Eastern Germany, with a planned later follow-up to monitor changes in attitudes with regard to influenza and influenza vaccination over time. We compared these results in the context of the current SARS-CoV-2 pandemic with a survey conducted between November, 16, 2020 and January 15, 2021 (influenza season 2020/2021). In total, EDs from 14 hospitals were invited to participate in the survey and answers were received from 11 and 12 departments in 2016/2017 and 2020/2021, respectively (Universitätsklinikum Regensburg, Klinikum Memmingen, Klinikum Weiden, München Klinik Harlaching, Klinikum Rosenheim, Klinikum Augsburg, Klinikum St. Marien Amberg, Klinikum Dritter Orden München, Klinikum Kempten, Klinikum St. Elisabeth Straubing, Krankenhaus Cham, Klinikum Ingolstadt). Additional questions were asked in the survey of 2020/2021 regarding the current COVID-19 pandemic and its potential impact on influenza vaccination. A full sample questionnaire (in German) can be obtained from the authors. The study was approved by the ethics committee of the University of Regensburg (IRB number 19-1631-101).

Sample recruitment and data collection

Sample recruitment and data collection followed the same procedure in both seasons. The sample consisted of emergency department personnel working in Bavarian hospitals (including university hospitals, municipal/country hospitals and hospitals under church sponsorship, with a capacity ranging from 480 to 1100 beds). The average annual number of ED patients ranged from 26000 to 48000. Physicians (and medical students), as well as nurses and others (mostly administrative personnel) participated in the survey. Participation was voluntary and uncompensated, and the questionnaire was anonymous and self-administered on a paper-pencil basis. Initially, the heads of the emergency departments in various hospitals in Bavaria were asked to participate in the study. After positive feedback, version 1 of the questionnaire (including questions on ED size and the requested number of questionnaires for participating personnel) was sent to the ED heads. Based in the information obtained herein, version 2 of the questionnaire (for ED personnel itself) was sent to the leaders of the emergency departments and distributed locally by them. In total, 727 questionnaires were sent to the different hospitals. The response rate was calculated from the total number of completed questionnaires returned back (142 and 190 in 2016/2017 and 2020/2021, respectively) divided by the total number of questionnaires sent out (229 in 2016/2017 and 498 in 2020/2021). Contacted EDs with no completed survey from ED staff were excluded (n = 2).

Query and variables

The questionnaire was loosely built on previous work on influenza vaccination and perceptions among hospital personnel [18, 19]. It included the categories ‘influenza’, ‘influenza vaccination’ and ‘socio-demographics’. For the 2020/2021 season, the category ‘impact of COVID-19 on influenza vaccination’ was added. In the ‘influenza’ category, the frequency of the disease and its complications as well as the impact on the ED were asked to be assessed on a 5-Point Likert scale. The listed side effects are a selection based on previous studies [19]. The ‘influenza vaccination’ category comprised knowledge questions on vaccination statements and the current recommendations of the STIKO on a binary scale as well as an estimation of vaccination side effects on a 6-Point Likert scale. Additionally, participants were asked about their influenza vaccination history and reasons for/against the vaccination (single choice), if they would recommend influenza vaccination to colleagues (binary scale), the future handling of the influenza vaccination in EDs (5-Point Likert scale), the current vaccination situation in their EDs (binary scale) and some ethical questions about influenza and vaccination (5-Point Likert scale). The category ‘impact of COVID-19 on influenza vaccination’ assessed a possible impact of the COVID-19 pandemic on influenza vaccination rate (binary scale). Socio-demographic questions asked included gender, age, profession and years working in the ED (single choice).

Statistical analysis

Statistical analysis was carried out using R version 3.6.2. Groups were compared using Mann-Whitney U tests for ordinal or continuous variables and chi-square tests for categorical variables. Logistic regression was used to compute odds ratios in a multivariable model. Survey items on a Likert scale were analyzed using the ’likert’ package in R [20]. Differences in the answer distributions between two groups were explored by comparing means using Mann-Whitney U tests after converting ordinal answer levels to a numeric scale [21]. P-values <0.05 were considered significant. The comparison between vaccinated and unvaccinated participants was limited to the 2020/2021 season to ensure that all variables were available for analysis including the items pertaining to the SARS-CoV-2 pandemic.

Results

In total, 332 ED personnel completed the survey, 142 (43%) of these in the 2016/2017 season and 190 (57%) in 2020/2021. Response rates were 62% and 38% in 2016/2017 and 2020/2021, respectively (ranging from 23%–100% in 2016/2017 and from 16%–72% in 2020/2021 per ED). Locations of participating EDs are depicted in Fig 1.

Fig 1. Locations of participating EDs.

Fig 1

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The map locates the participating EDs within Bavaria, South-Eastern Germany. EDs participating in both seasons are depicted as filled dots, unfilled dots represent EDs participating in 2020/2021 only. Dot size is proportional to the number of returned surveys from each site.

In both years, more surveys were completed by women and nurses. There were no statistically significant differences, however, among respondents in both seasons regarding gender, older age (> 44 years) and profession (Table 1).

Table 1. Factors associated with influenza vaccination status and socio-demographics of participants.

Characteristics univariate both years
2016/2017
N = 142 1 		2020/2021
N = 190 1 		p-value 2
vaccinated this season 44/142 (31%) 112/190 (59%) <0.001
vaccination available on site (ED) 27/141 (19%) 94/189 (50%) <0.001
≥ 2 times vaccinated 56/142 (39%) 110/190 (58%) 0.001
gender 0.5
 male 57/136 (42%) 68/183 (37%)
 female 79/136 (58%) 115/183 (63%)
age
 >44 45/38 (33%) 58/190 (31%) >0.9
profession 0.069
 nurses 75/142 (53%) 102/190 (54%)
 other 19/142 (13%) 12/190 (6%)
 physician/student 48/142 (34%) 76/190 (40%)
Characteristics univariate 2020/2021 multivariate 2020/2021
not vaccinated
N = 78 1 		vaccinated
N = 112 1 		p-value 2 OR 3 95% CI 4 p-value 2
vaccination available on site (ED) 31/77 (40%) 63/112 (56%) 0.044 3.96 1.42, 12.2 0.011
≥ 2 times vaccinated 17/78 (22%) 93/112 (83%) <0.001 21.3 7.41, 73.4 <0.001
intending to be vaccinated because of COVID-19 2/75 (3%) 55/111 (50%) <0.001 86.7 18.8, 688 <0.001
profession <0.001
 nurses 61/78 (78%) 41/112 (37%) - -
 other 3/78 (4%) 5/112 (5%) 1.39 0.11, 15.2 0.8
 physician/student 14/78 (18%) 66/112 (59%) 5.39 1.83, 17.2 0.003
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1 Statistics presented: n/N (%)

2 Statistical test performed: chi-square test of independence

3 Odds Ratio

4 CI = Confidence Interval

Of the 332 respondents overall, 156 (47%) reported having been vaccinated against influenza in the respective season, while 176 (53%) had no current vaccination. Comparing the two seasons, both the vaccination rate in the respective season as well as the rate of ED personnel that reported at least two vaccinations were significantly higher in 2020/2021. Also, significantly more respondents reported that vaccinations were offered on site (in the ED) in 2020/2021.

In order to explore the observed increase in influenza vaccination coverage, factors with a significance level of p<0.1 in the comparison between both seasons were carried over to compare vaccinated and unvaccinated respondents in the 2020/2021 season. Vaccination offered on site, being vaccinated at least twice and profession (physician or medical student) as well as the intention to get vaccinated because of COVID-19 were associated with a significantly higher vaccination coverage in 2020/2021 in univariate and multivariate analysis (Table 1).

Most questionnaire items related to influenza incidence and complications revealed no significant differences between 2016/2017 and 2020/2021 seasons as well as between vaccinated and not vaccinated respondents in 2020/2021. The only exceptions were that, compared to 2016/2017, 2020/2021 respondents estimated a higher influenza death rate whereas the infection rate among nurses was estimated to be higher by vaccinated respondents than by unvaccinated participants in 2020/2021 (Fig 2).

Fig 2. Comparison of estimated frequencies of influenza infections and complications between 2016/2017 and 2020/2021 or between vaccinated and unvaccinated respondents in 2020/2021.

Fig 2

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Estimated frequency of influenza infection and its complications rates were assessed on a 5-Point Likert scale and compared between the seasons 2016/2017 and 2020/2021 (left) or between vaccinated and not vaccinated respondents in 2020/2021 (right). Statistics were performed after conversion of ordinal answer levels to a numeric scale using Mann-Whitney U tests, p-values are depicted as *<0.05, **<0.01 and ***<0.001.

The perception of side effects associated with influenza vaccination did not change between the two seasons. In contrast, unvaccinated personnel (2020/2021) consistently estimated significantly higher frequencies of all potential vaccination side effects listed in the survey (headache, body aches, fever, shivering, skin necrosis, unable to work, encephalitis)—with the notable exception of local pain at the injection site that was estimated to occur frequently by both groups (Fig 3).

Fig 3. Comparison of estimated frequencies of influenza vaccination side effects between 2016/2017 and 2020/2021 or between vaccinated and unvaccinated respondents in 2020/2021.

Fig 3

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Estimated frequency of side effects associated with influenza vaccination assessed on a 6-Point Likert scale was compared between the seasons 2016/2017 and 2020/2021 (left) or between vaccinated and not vaccinated respondents in 2020/2021 (right). Statistics were performed after conversion of ordinal answer levels to a numeric scale using Mann-Whitney U tests, p-values are depicted as *<0.05, **<0.01 and ***<0.001.

With regard to the burden of influenza on the ED, more participants from 2020/2021 agreed that influenza poses a serious threat for ED patients. Vaccinated participants in 2020/2021 were more likely to agree that influenza poses a heavy burden on ED resources. With regard to ethical questions related to influenza and patient care, we observed significant differences between unvaccinated and vaccinated respondents (2020/2021), whereas answers between 2016/2017 and 2020/2021 respondents were virtually the same. In 2020/2021, vaccinated respondents were significantly more likely to agree that influenza vaccination should be mandatory and that no-shows during an influenza pandemic should be laid off. In contrast, unvaccinated respondents were significantly more likely to agree (i) that a mandatory vaccination policy would be a reason to change jobs, (ii) that it would be ethical not to go to work during an influenza pandemic and (iii) that work attendance should be left to the employee. Of note, both groups agreed to a high percentage on a moral obligation to care for influenza infected patients (Fig 4).

Fig 4. Comparison of views on the burden of influenza in the EDs and ethical attitude of employees towards vaccination and work attendance.

Fig 4

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Acceptance of statements on the impact of influenza on EDs and various ethical issues related to influenza (vaccination) or work attendance assessed on a 5-Point Likert scale was compared between the seasons 2016/2017 and 2020/2021 (left) or between vaccinated and not vaccinated respondents in 2020/2021 (right). Statistics were performed after conversion of ordinal answer levels to a numeric scale using Mann-Whitney U tests, p-values are depicted as *<0.05, **<0.01 and ***<0.001.

Discussion

Health care workers are frequently exposed to contagious agents. In particular, the close and extended contact to vulnerable patients and individuals with acute respiratory infections like influenza in the ED leads to an enhanced risk of transmitting nosocomial diseases [9–11]. Even though vaccination of ED personnel and health care workers in general is considered to be a reliable and effective method to decrease nosocomial influenza infections and is recommended by the German standing vaccination committee (STIKO) [22, 23] the vaccination coverage within hospitals can still be improved.

In order to analyze the acceptance of influenza immunization, we conducted a survey to explore influenza vaccination coverage and attitudes towards influenza and influenza vaccination among emergency department personnel and found that self-reported vaccination coverage significantly increased from 31% in the 2016/2017 season to 59% in the 2020/2021 season, i.e. before and during the COVID-19 pandemic. These numbers may seem low but are in the range reported previously by similar studies where self-reported seasonal influenza vaccination coverage among health care workers, ED staff and emergency medical services (EMS) personnel was around 40% (28%–54%) [4, 9, 11, 24–26]. Along with the higher vaccination rate in 2020/2021 compared to 2016/2017 we observed a significantly increased proportion of employees reporting availability of influenza vaccination on site (in the ED) and a history of at least two influenza vaccinations. Beyond that, we found no major changes in the data over time, except for the fact that employees in 2020/2021 we more likely to agree that influenza poses a serious threat for ED patients and considered fatal complications of influenza infections to occur more frequently. It is tempting to speculate that the close proximity to the pandemic caused by another respiratory virus might have influenced the assessment. Notably, during the same period, the perception of vaccination associated side effects, as well as attitudes towards more ethical questions related to influenza and patient care remained unchanged. Based on these observations we studied factors linked to the vaccination status in the 2020/2021 season in an univariate and multivariate analysis. We hypothesized that the COVID-19 pandemic (among other reasons) would positively affect the influenza vaccination rate among ED personnel. Indeed, answers that were positively associated with being vaccinated were the availability of influenza vaccination on site (in the ED), a history of at least two influenza vaccinations, profession (being a physician or medical student) and the intention to get vaccinated because of COVID-19. Higher vaccination coverage rates among health care workers due to on site vaccination services were also demonstrated in previous studies with an increase in vaccination coverage rates between +4% and +29% [27–31]. Profession and vaccination history have been associated with being vaccinated against influenza before [26, 32]. A monocentric study from Switzerland reported odds ratios of 7.7 and 9.5, respectively [25]. During the COVID-19 pandemic, Wang et al. also observed a more positive attitude towards influenza vaccination among nurses possibly based on a heightened awareness of the risks associated with airborne infections [16]. In the course of the current increased awareness, targeted education and information about the mode of action and safety of the influenza vaccination is of particular importance to eliminate misleading media reports and doubts about the effectiveness of vaccination. In addition, promotional activities and campaigns in newsletters, salary supplements, mailings, posters, or fact sheets support achieving higher vaccination coverage rates, as reported in other studies with increases ranging from +12% to +26% [33–35]. Another very effective tool to increase vaccination rates among health care workers is a change in policy with mandatory vaccination [31, 36–39]. In studies conducted in the United States or Australia, increases in vaccination coverage rates ranged from +24% to +46%. Although the results are impressive, mandatory influenza vaccination is not an option in many health care systems including Germany (influenza vaccination is free but not mandatory for hospital employees).

With regard to questions pertaining to influenza incidence and complications, we found no major differences between vaccinated and not vaccinated respondents in 2020/2021, apart from higher estimates for risk of infection for nurses among vaccinated employees compared to unvaccinated respondents. In addition, unvaccinated ED personnel estimated significantly higher frequencies of vaccination side effects compared to their vaccinated colleagues. Together with concerns about vaccine effectiveness [11, 16, 17, 25, 26, 40], concerns about side effects and vaccine safety have been identified as a major obstacle for vaccination of health care workers before [24–26, 40]. Similarly, belief in vaccine safety and effectiveness was higher in vaccinated than in unvaccinated EMS personnel [11]. Another concern previously raised by ED staff was that illness could be caused by the vaccine [9].

This study also examined the association of ethical attitudes and influenza vaccination, which provides an important and unique contribution to influenza vaccination research. In our study, vaccinated and unvaccinated ED personnel in 2020/2021 also differed in their attitudes towards ethical questions raised. Whereas both groups agreed to a high percentage on a moral obligation to care for influenza patients and assessed influenza as a heavy burden on their resources, unvaccinated respondents were less likely to accept lay-offs for employees not showing up for work and rather stated that work attendance should be the employee’s decision (both during a potential influenza pandemic). Vaccinated participants on the other hand, would rather agree that vaccination should be mandatory and were less likely to consider job changes in the event of a mandatory vaccination policy. A significant role for employers’ vaccination policy but low support for mandatory vaccination has also been reported from emergency medical personnel before [11].

Several aspects might limit the generalizability of our findings. The study is not representative for all EDs in the surveyed area of Bavaria, Germany, and only a part of the employees answered the questionnaire. The response rate of 38% in the 2020/2021 season may seem low but can be explained as of the higher number of questionnaires sent out to the emergency departments than in the 2016/2017 season. In general, the number of returned questionnaires in the 2020/2021 season is higher than the number in the 2016/2017 season. With regard to the distribution of the questionnaire, it must be noted that the respective ED leaders were responsible for the process and therefore multiple responses from a single employee cannot be ruled out.

Conclusion

Our results suggest that not only the assessment of influenza as a more serious risk during the current COVID-19 pandemic but also ease of access to vaccination is crucial for an increased influenza vaccination rate. In order to increase the influenza vaccination coverage among ED personnel, a broad effort to offer influenza vaccination on site in the ED might help. Given the observed differences in the perception of vaccine side effects among vaccinated and not vaccinated personnel, interventions targeting not only influenza disease but specific knowledge about vaccination and its side effects could help to overcome prejudices.

Acknowledgments

We would like to thank and acknowledge the work and crucial support by Christine Fuhrmann, Universitätsklinikum Regensburg; Dr. Rupert Grashey, Klinikum Memmingen; Dr. Andrea Dauber, Klinikum Weiden; Dr. Andreas Pohl, Klinikum Weiden; Dr. Florian Demetz, München Klinik Harlaching; Dr. Michael Bayeff-Filloff, Klinikum Rosenheim; PD Dr. Markus Wehler, Klinikum Augsburg; Dr. Marc Bigalke, Klinikum St. Marien Amberg; Dr. Kathrin Tzaferidis, Klinikum Dritter Orden München; Dr. Dagmar Strauß, Klinikum Kempten; Dr. Christian Thiel, Klinikum St. Elisabeth Straubing; Dr. Thomas Etti, Krankenhaus Cham and Dr. Stephan Steger, Klinikum Ingolstadt.

Data Availability

An anonymized version of the dataset is available at zenodo.org (https://doi.org/10.5281/zenodo.5164388).

Funding Statement

The authors received no specific funding for this work.

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Decision Letter 0

Jamie Males

20 Jul 2021

PONE-D-21-08907

Influenza vaccination coverage among emergency department personnel is associated with perception of vaccination and side effects, vaccination availability on site and the COVID-19 pandemic

PLOS ONE

Dear Dr. Hanses,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors present the results of two cross-sectional surveys of influenza vaccination uptake among ED personnel in Bavaria, Germany. The manuscript is well-written for the most part and the study findings are generally of interest; the methods require some clarification and the discussion section needs to be reworked. Specific suggests are as follows:

Abstract, line 27: The extremely low response rate in 2020-2021 is a threat to the validity of your findings and should be noted in the limitations section (which is missing from the paper).

Abstract, line 33: The pandemic is not a factor that differs across the study population; this could be tweaked to say something like "the effect of the pandemic on influenza vaccination intentions" or similar.

Introduction, line 52: Usually influenza vaccination is also recommended for those at increased risk of complications from influenza disease, regardless of their risk of acquiring influenza -- this could be noted here as well.

Methods, line 76: Given that the article presents a comparison with findings in the COVID-19 pandemic context and the earlier findings, it would be useful to include a brief note here or in the introduction about the impetus for the initial 2016-2017 survey -- i.e. was it motivated by a specific data point, a policy change, some other global context?

Methods, line 77: Are these 14 EDs the universe of EDs in Bavaria? If not, how many are there/what percentage is represented by the 14 invited, and how were they selected for recruitment?

Methods, lines 89-99: The sample selection requires substantial clarification. Were the 229 and 498 staff surveyed in each season all of the staff working in the ED -- or all of the physicians, nurses, and 'administrative' staff? (And if the latter, which types of staff does this exclude?) If this was not 100% of the staff in the targeted EDs, what proportion is represented by the disseminated and returned surveys? Also, please provide more detail on how specifically the surveys were disseminated -- e.g. were they mailed to individual staff? Was a package of surveys sent to the ED and distributed by a chief/leader? Was the package sent and the surveys were left on a table in the lunch room? Etc. If surveys were not addressed to individuals and they were returned anonymously, how did the authors assure that only targeted staff (from the ED) completed and returned surveys and that multiple surveys were not completed by a single person?

Results, Table 1: Please change "vaccinated because of COVID-19" to "intending to be vaccinated because..." or similar. As written it is confusing to see entries in the 'unvaccinated' category for this variable as the unvaccinated people clearly were not vaccinated because of COVID-19. I will also note that I found this table extremely difficult to follow; you might consider reformatting it or even breaking it up into multiple tables if the space allotted by the journal permits.

Results, line 148: The fact that the comparisons of unvaccinated with vaccinated persons include only data from 2020-21 should be noted at every point in the manuscript or tables/figures where these comparisons are made.

Results, line 157: Higher risk relative to what, or whom? E.g. higher than the general public, higher than doctors...?

Results, line 160: For this and all of the figures, the figure titles need to be more descriptive so that they can be interpreted without reading the text. I would also suggest including in the figure title that the figures compare 2016-17 to 2020-21 and compare unvaccinated to vaccinated persons.

Results, line 169: How was this list of possible vaccine side effects selected? Skin necrosis and encephalitis are essentially nonexistent as a result of influenza vaccination, whereas mild systemic symptoms and injection site pain would commonly be expected. Also, how were these presented in the survey? Listing very serious and extremely rare side effects alongside mild and common side effects could potentially bias respondents' selections.

Results, line 184: As noted above, you would need to emphasize here that this comparison was only done for 2020-2021 -- however, did you attempt to combine data across seasons to see if the same associations with vaccination status persist? (I assume this comparison was not made for 2016-2017 due to the small sample of people vaccinated; however, this could be clarified in the text as well.)

Discussion, general comment: The discussion substantially reiterates the introduction and results sections. Repetitive content should be streamlined so additional interpretation of findings can be excluded. Areas that seem redundant and could be deleted entirely or reduced to a single sentence include lines 213-217 and 223-230.

Discussion, lines 201-206: This should be noted in detail in the introduction as context and then briefly restated here in the discussion if needed.

Discussion, lines 207-212: Some of this is already in the introduction and could be deleted; the parts that are not in the introduction already might more properly belong there as they provide justification for the importance of this study.

Discussion, lines 231-234: It would be helpful here to include some suggested actions to take based on these findings or at least the implications of the findings as nurses presumably provide substantial amounts of care in the ED and are at least equally as much at risk of acquiring and transmitting influenza as physicians.

Discussion, lines 236-239: It's confusing when you bounce back and forth between the comparison across time and the comparison of unvaccinated with vaccinated personnel in the 2020-2021 season. I would recommend a discussion paragraph talking about differences and similarities over time, and then a separate paragraph discussing differences observed by vaccination status in 2020-2021.

Discussion, lines 249-250: Beyond the question of vaccination mandates, I have never seen a published study that examines ethical attitudes and their association with influenza vaccination before -- at least not with a suite of items used together like this. In my view, this is an unique and significant contribution of your study. I would create a separate paragraph focusing on the ethics questions/findings and implications for pandemic preparedness, vaccination promotion, etc.

Discussion, line 259: As noted above, the manuscript lacks a limitations section; one should be added here.

Conclusion, line 261: I did not see a measure of awareness in this study; this should be rephrased to reflect what was actually asked in the survey.

Conclusion, lines 263-264: This finding is extremely important for increasing rates of influenza vaccination in Bavarian EDs because it is actionable and the necessary intervention is obvious. I strongly suggest adding to your discussion a supporting paragraph that discusses the change in onsite vaccine offering over time, any national or regional policies or practices that might support or be a barrier to this (e.g. do Germans have nationalized or private healthcare that might complicate payment; is there a national or regional policy to provide free influenza vaccine to healthcare workers; is there a national or regional target for influenza vaccination, etc.). It might be useful to cite the findings of the U.S. Task Force on Community Preventive Services, which found strong evidence that offering vaccination onsite increases vaccination coverage. Although the Task Force is convened in the U.S., the evidence considered is global and the findings are certainly applicable to the Bavarian context: https://www.thecommunityguide.org/findings/worksite-health-seasonal-influenza-vaccinations-healthcare-on-site. In conjunction with this, some of the studies in other countries noting the association of onsite offering of vaccine with vaccination uptake among HCP could be included.

Conclusion, lines 266-267: I am not aware of any evidence that education/communication campaigns when used alone are effective in increasing vaccination uptake, so I would not term these "most beneficial". I suggest recommending this type of effort in conjunction with onsite offering of influenza vaccine as discussed above.

Figures 2-4: The labels on individual figure entries need to be edited to be more specific as many are not interpretable without a copy of the survey instrument - and this would not be helpful to readers who do not speak German. I would recommend an appendix with the translated survey instrument, but if this is cost- or time-prohibitive, the labels for each entry in the figure should be written as complete phrases or sentences that capture what was actually presented to survey respondents, e.g. "I believe influenza results in death at this frequency" instead of "influenza complications - death".

Reviewer #2: This article is well written. Methodology seems sound. Conclusions were pretty predictable.

I have three questions :

1- Could the authors please elaborate on the fact that vaccination was not available on sit everywhere ? It seems odd that it is not the case in every setting. Could you please describe what health care workers have to do to be vaccinated when flu vaccine is not available on site ?

2- Do they authors have the 2020/2021 national vaccination coverage in physicians and nurses as a comparator ?

3- Could you precise others categories than administrative personnel in the non physicians or nurses people ? Did you survey other personnels in contact with patients such as cargivers known for their low vaccine coverage (even lower than nurses’ one) ?

**********

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Reviewer #1: No

Reviewer #2: Yes: Paul Loubet

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PLoS One. 2021 Nov 19;16(11):e0260213. doi: 10.1371/journal.pone.0260213.r002

Author response to Decision Letter 0

2 Sep 2021

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. …

We have checked PLOS ONE´s style requirements again and hope everything is correct now.

2. Please provide additional details regarding participant consent …

We thank you for pointing this out. As the data were collected anonymously, self-administered and on a voluntary basis, no consent was obtained for this study. For more details please see lines 110-112.

3. Please provide the names of the participating EDs.

Thank you for this suggestion. We have made the change and added the names of the participating EDs. Please see lines 95-98.

4. please provide the date ranges when surveys were collected during the two seasons.

We apologize for not pointing this out. We have corrected the methods part and you can find the date ranges in lines 86-87 as well as in lines 90-91.

5. In your Data Availability statement, you have not specified where the minimal data set underlying the results described in your manuscript can be found. …

This observation is correct. An anonymized version of the dataset is available from zenodo.org

(https://doi.org/10.5281/zenodo.5164388). "

Reviewers' comments:

Reviewer 1:

Abstract, line 27: The extremely low response rate in 2020-2021 is a threat to the validity of your findings and should be noted in the limitations section (which is missing from the paper).

We thank the reviewer for pointing this out. We have added a limitation section at the end of the discussion, which, among others, concerns to the response rate in 2020/2021. Please see lines 339-342.

Abstract, line 33: The pandemic is not a factor that differs across the study population; this could be tweaked to say something like "the effect of the pandemic on influenza vaccination intentions" or similar.

We agree and have updated this sentence. Please see line 31.

Introduction, line 52: Usually influenza vaccination is also recommended for those at increased risk of complications from influenza disease…

Thank you for this important observation. We have changed this section. Please see lines 54 and 60-61.

Methods, line 76: Given that the article presents a comparison with findings in the COVID-19 pandemic context and the earlier findings, it would be useful to include a brief note … about the impetus for the initial 2016-2017 survey…

We have revised the text to address your concerns and explained in more detail the impetus for the first survey in 2016/2017 and the linkage to the second survey. Please see lines 85-93.

Methods, line 77: Are these 14 EDs the universe of EDs in Bavaria? If not, how many are there/what percentage is represented by the 14 invited, and how were they selected for recruitment?

We thank the reviewer for pointing this out. We added this information to the limitations at lines 337-339.

Methods, lines 89-99: The sample selection requires substantial clarification. … Also, please provide more detail on how specifically the surveys were disseminated ...

We agree and have corrected the sample recruitment part with a more detailed explanation of the process. Please see lines 113-117. We also revised the text to include your concerns about multiple surveys in the new limitations section. Please see lines 343-345.

Results, Table 1: Please change "vaccinated because of COVID-19" to "intending to be vaccinated because..." … you might consider reformatting it or even breaking it up into multiple tables …

We have made the changes and thank the reviewer for these suggestions. Please see lines 165-171.

Results, line 148: The fact that the comparisons of unvaccinated with vaccinated persons include only data from 2020-21 should be noted at every point in the manuscript or tables/figures where these comparisons are made.

We have taken note of this important observation and added the note in the certain text passages. Please see lines 29,36,199,204, 215,220,223,224,239,327.

Results, line 157: Higher risk relative to what, or whom

We agree that this information is missing and added the comparison group in lines 190-191.

Results, line 160: …the figure titles need to be more descriptive so that they can be interpreted without reading the text. I would also suggest including in the figure title that the figures compare 2016-17 to 2020-21 and compare unvaccinated to vaccinated persons.

We´ve revised the figure titles to become more descriptive and changed the figure titles as suggested. Please see lines 194-201, 210-217, 233-240.

Results, line 169: How was this list of possible vaccine side effects selected… Also, how were these presented in the survey? Listing very serious and extremely rare side effects alongside mild and common side effects could potentially bias respondents' selections.

We thank the reviewer for pointing this out. The list of side effects was loosely built on previous studies, which we added in the method part (query and variables) in lines 129-130. The order of the side effects listing in the paper is almost the same than in the questionnaires. Also, we thank you for your concern regarding the alongside listing of mild, extreme and almost nonexistent side effects listings. We are aware that some effects are very rare. However, this was done intentionally to determine whether effects were partially overestimated.

Results, line 184: … did you attempt to combine data across seasons to see if the same associations with vaccination status persist? …

This observation is correct and the comparison would be interesting, but in 2016/2017 season, the items pertaining to the SARS-CoV-2 pandemic was not included so this variable would be missing. We explained that in more detail in lines 148-150.

Discussion, general comment: … Areas that seem redundant and could be deleted entirely or reduced to a single sentence include lines 213-217 and 223-230.

We thank the reviewer for this suggestion. We agree and have changed this part of the discussion. Please see lines 263-268 and 282-285.

Discussion, lines 201-206: This should be noted in detail in the introduction as context and then briefly restated here in the discussion if needed.

We´ve corrected this part of the discussion as we agree on the reviewers suggestion. Please see lines 54-60, 64-67 and 249-254.

Discussion, lines 207-212: Some of this is already in the introduction and could be deleted…

We revised the discussion and introduction part and thank the author for this suggestion. Please see lines 51-52, 243-249 and 255-259.

Discussion, lines 231-234: It would be helpful here to include some suggested actions to take based on these findings …

We thank the reviewer for this comment and have added a section with suggested actions for a higher vaccination rate. Please see lines 297-308.

Discussion, lines 236-239: … I would recommend a discussion paragraph talking about differences and similarities over time, and then a separate paragraph discussing differences observed by vaccination status in 2020-2021.

We agree that this part of the discussion was confusing. We have revised the structure of the discussion as the reviewer suggested. Please see lines 271-290 and 310-317.

Discussion, lines 249-250: I would create a separate paragraph focusing on the ethics questions/findings and implications for pandemic preparedness, vaccination promotion, etc.

We thank the reviewer for this pleasing assessment. We have extended the ethical findings sections. Please see lines 325-330.

Discussion, line 259: As noted above, the manuscript lacks a limitations section; one should be added here.

We apologize for the missing limitation section, which was now included in the last part of the discussion. Please see lines 337-345

Conclusion, line 261: I did not see a measure of awareness in this study; this should be rephrased to reflect what was actually asked in the survey.

We have corrected the term and changed it into the assessment of influenza as a more serious risk. Please see lines 348-349.

Conclusion, lines 263-264: … I strongly suggest adding to your discussion a supporting paragraph that discusses the change in onsite vaccine offering over time…

We thank the reviewer for his important notes and added some reference papers to our study. Please see lines 290-293.

Conclusion, lines 266-267: … I would not term these "most beneficial". I suggest recommending this type of effort in conjunction with onsite offering of influenza vaccine as discussed above.

We have changed the text according to the reviewer´s suggestion. Please see line354-355

Figures 2-4: The labels on individual figure entries need to be edited to be more specific as many are not interpretable without a copy of the survey instrument …

We agree to the reviewer´s comment and described the items on the figures in more detail. Please see Figures 2-4.

Reviewer 2:

I have three questions :

1- Could the authors please elaborate on the fact that vaccination was not available on sit everywhere? …

Thank you for your questions, which we would like to address in more detail. In Germany, vaccinations are generally free of charge for hospital employees. However, vaccinations do not take place exclusively in the ED, but can also be given, for example, via an appointment with the company doctor.

2- Do they authors have the 2020/2021 national vaccination coverage in physicians and nurses as a comparator ?

Unfortunately, the requested data is not yet available.

3- Could you precise others categories than administrative personnel in the non physicians or nurses people ? Did you survey other personnels in contact with patients such as cargivers known for their low vaccine coverage?

We thank the reviewer for this important question. The others category only includes non medical staff (mainly administrative). Caregivers were not included in this survey, only registered nurses.

Attachment

Submitted filename: Response to Reviewers.docx

Click here for additional data file. (24.8KB, docx)

Decision Letter 1

Megan Lindley

5 Nov 2021

Influenza vaccination coverage among emergency department personnel is associated with perception of vaccination and side effects, vaccination availability on site and the COVID-19 pandemic

PONE-D-21-08907R1

Dear Dr. Hanses,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. As one of the previous reviewers (Reviewer #1), I found your revision to be extremely responsive to all of my comments and I appreciate your time in carefully addressing each of the stated concerns. The revised manuscript provides the necessary context for your findings and is organized in a way to highlight the comparisons made over time as well as by vaccination status and the unique contribution of the ethical/values data gathered. 

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Megan C. Lindley

Guest Editor

PLOS ONE

Additional Editor Comments (optional):

The authors' conscientious response to the previous review comments is much appreciated. The revised manuscript is much improved and highlights the unique contributions of the authors' research.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #2: Yes

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6. Review Comments to the Author

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Reviewer #2: Thank you for having adressed my comments. I have no other comments

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Reviewer #2: Yes: Paul Loubet

Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

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    Submitted filename: Response to Reviewers.docx

    Click here for additional data file. (24.8KB, docx)

    Data Availability Statement

    An anonymized version of the dataset is available at zenodo.org (https://doi.org/10.5281/zenodo.5164388).

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