Discussion
The main finding from this survey performed among GPs in four EU countries was that the use of any specific vaccine type in the <65y risk group is determined by the availability of specific vaccine type(s) at the clinic level at a given point in time. In addition, for those ≥65y, availability of multiple vaccine types at the clinic level was more common and specifically in this situation the individual characteristics of the vaccinees, notably older age and the presence of multiple comorbidities, play a major role in GPs’ choice of vaccine type.
Multiple influenza vaccines types exist. In Europe, conventional trivalent vaccines are being replaced by quadrivalent vaccines and new vaccine types, such as high-dose and cell-based vaccines, are introduced while adjuvanted vaccines have been available longer in some countries, but more recently in others. In the countries studied, local vaccine recommendations recommend one or more specific vaccine types for different risk groups [9–12]. This is also the case in other countries, for example in Europe in Germany [14], Finland [15], Ireland [16], and Spanish regions [17, 18], and beyond in Australia [19] and Canada [20]. It was unknown if in practice GPs have access to more than one vaccine type for each risk group, and if so, how they choose between vaccine types for each individual in a risk group. Only one vaccine type was available for the majority of GPs vaccinating children 9-17y or 10-17y in Austria and Italy, adults 18-64y in Austria, Italy and the UK and adults ≥65y in the UK. More than one of the recommended vaccine types was available for almost half of Austrian GPs vaccinating those with chronic conditions or immunosuppression (of any age) and adults ≥65y, and for the majority of GPs vaccinating adults ≥65y in Italy and Spain.
Vaccine type availability was observed as a determinant of vaccine type use among those aged <65y irrespective of the existence of recommendations for multiple vaccine types; because only a subset of the recommended vaccine types is made available, or alternatively due to fluctuating vaccine stock. In Austria, Italy and Spain, several GPs indicated that they have encountered bottlenecks in deliveries of vaccines or insufficient stock. Future work may try and explore the underlying reasons for these observations. In Italy, the vaccine viewed by the GP as most appropriate vaccine may not always be administered, as evidenced by surveys among Italian GPs by Levi et al. and Boccalini et al., showing that in the season 2014–2015 more than half of the local health units (60%) did not always allow GPs to choose the type of vaccine for their patients [21], and in the season 2017–2018 only half the GPs had a sufficient number of all available vaccine types they needed [22]. Fluctuations in vaccine availability effectively mean that, even if throughout the season different vaccine types are available to a GP for a risk group, at specific points in the season GPs effectively do not have a choice between vaccine types. Consequently, in this situation vaccine availability is not expected to bias vaccine effectiveness estimation.
The most frequently mentioned patient characteristics to influence choice of vaccine type across all countries (except the UK where typically only one vaccine type was available) were older age followed by the presence of multiple comorbidities. GPs who explained how this affects their vaccine choice indicated they were more likely to choose adjuvanted TIV in the presence of these characteristics. This choice is appropriate as it is in line with the vaccine recommendations in Italy and Valencia which preferentially recommend the adjuvanted vaccine to older age groups due to increased immunogenicity, and is consistent with the findings on more immunogenic vaccines by Boccalini et al. [9, 11, 22–24]. Similarly, in this aforementioned GP survey among Italian GPs it was clear that the majority of GPs were aware that not all influenza vaccines are the same and that some vaccines are preferable to others for some population groups [22]. Knowing that specific vaccine types are sometimes channelled to older and more frail subjects is relevant in an era where vaccine diversity is increasing and likewise IVE studies are stratified by vaccine type or even vaccine brand, because it can introduce bias that should be appropriately accounted for.
The perception of different brands of a single vaccine type was less clear than the perception of different vaccine types. Most GPs in Austria, Italy and Spain perceive different brands of egg-based QIV to be clinically equivalent, whereas nearly half the GPs in the UK did not, although almost all had only a single brand of egg-based available.
Differences were observed between the four countries in how seasonal influenza vaccine is offered to individuals in risk groups that are part of the vaccine recommendations. Whilst the main approach in Austria, Italy and Spain is to offer influenza vaccine when patients present to the practice, in the UK all risk patients are contacted. In addition, GPs in the UK receive financial incentives to deliver influenza vaccinations whereas GPs in the other countries do not [25]. These factors may contribute to the higher vaccine coverage among adults ≥65y observed in the UK (72.0% in 2018–2019 [26]) compared to the other countries (53.1% in Italy [27] and 52.1% in Spain [28] in 2018–2019, 14% in Austria in 2015–2016 [29]. Whilst most GPs in Austria, Italy and Spain believe that patients who perceive themselves to be a higher risk or who are more health conscious are more likely to accept influenza vaccination, this was only the case for respectively half and two thirds of GPs in the UK (although sample size was small). One explanation for this could be that in the UK vaccination is the norm (with its school-based programs for children [26] and vaccine coverage in adults ≥65y is among the highest in Europe [7]). Prior research using discrete choice experiments has shown that the propensity to vaccinate increases with increasing vaccine coverage among acquaintances and in the population [30, 31]. Influenza vaccine acceptability in the UK may therefore be less susceptible to individual perception of vaccination than in other countries. Furthermore, in Austria influenza vaccination is not offered free of charge and patients usually have to buy the vaccine at the pharmacy prior to administration at the GP practice, which may constitute a barrier to vaccine uptake [29, 32]. Accessibility has previously been shown to be an important determinant of vaccination [30, 31]. Finally, GPs emphasized the importance a patient’s trust in the GP and health services and provision of adequate information on vaccination were important drivers of vaccine acceptance.
Study limitations
In three countries, GPs were selected based on their participation in the national sentinel influenza surveillance (Austria, Italy) and/or the DRIVE IVE studies (Austria, UK), and may therefore not be representative of all GPs in the country. Few characteristics on GPs were collected. However, within each country, responding GPs came from a wide geographic distribution. The number of GPs surveyed in the UK was relatively low, which makes the results less representative for GPs in the UK in general; however it provides full representativeness of all GPs participating in the DRIVE network 2019/20. For the Italian survey, there was no active approach to solicit completion of the survey, hence the relatively low response rate was to be expected. The higher response rates in Austria and the UK were likely due to the direct personal outreach. Non-response bias cannot be excluded; for example GPs participating in the survey could be more interested in influenza which may translate in differences in how they approach the seasonal influenza vaccination campaigns. GPs were asked about any bias in vaccine choice they may have; if there is hesitancy to admit that the true impact of patient characteristics on vaccine choice may be larger. In all four surveys, the question on whether the GP’s choice of vaccine type was directed by vaccine availability could have been more elaborate, to better understand if fluctuating stock plays a role.
10.1371/journal.pone.0252836.r001
Decision Letter 0
Seale
Holly
Academic Editor
2021
Holly Seale
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version
0
15 Mar 2021
PONE-D-21-00741
Factors driving choices between types and brands of influenza vaccines in general practice in Austria, Italy, Spain and the UK
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Reviewer #1: This paper presents the descriptive results of a survey conducted among GP's in four European countries on how they promote influenza vaccination in their clinics and how they choose which influenza vaccine to administer to patients. These findings have implications for vaccine effectiveness estimates, as well as offer insight into vaccine selection when multiple influenza vaccine options are available. The statistical methods used are basic, but I believe they are appropriate.
Specific comments below:
Introduction: nicely written
Methods:
- Lines 130-133: The methods do not explain how open-ended responses were analysed and categorised into themes. Please describe what methods were used. Were themes defined a priori?
- It would be interesting to know how the survey questions were developed. Were they derived from previous research or designed specifically for this study? If the latter, was any theoretical framework used in their development?
Discussion:
-The first paragraph is somewhat repetitive at times. For example, lines 291-296 and lines 313-315 present similar information, as well as lines 335-337 and 304-307 . I suggest rewriting the paragraph to make it somewhat more concise.
-Lines 378-380: As you mention, response rates in Italy were quite low (14%). It would be helpful to have some more discussion on how this may have biased results.
Reviewer #2: Review comments for manuscript: Factors driving choices between types and brands of influenza vaccines in general practice in Austria, Italy, Spain, and the UK
As an important component to advancing evaluation of effectiveness of influenza vaccines, Anke L et al conducted a descriptive study to describe the factors that influence the choice in use of influenza vaccine types and brands among general practitioners and risk category vaccinees in four European Countries.
Annually, several influenza vaccines are recommended in Europe. Factors influencing the use of these vaccines are many and can vary by health providers as well as by those getting vaccinated. The authors conducted a study to better understand these factors in 4 European countries. The research question/s proposed by the authors are of public health importance.
Overall, the manuscript is well written. It is easy to read.
Specific comments:
Methods: The research methods are clear and straightforward. However, the inclusion of Spain-Valencia is somewhat confusing given it was not participating in the DRIVE project. The choice of this site requires a stronger rationale (Line 94-98). Or was it convenient?
Information on how the reliability of the survey tool used was assessed would be beneficial to add. Similarly, regarding the online survey tool, information has not been provided on whether participation could occur more than once?
Details on the sample size that was sufficient to answer the study questions are missing.
Results
The results are well presented.
Table 2, lines 145-150: the numbers in parenthesis are not clearly explained and this is somewhat confusing.
Some results are presented as absolute numbers only; other results are presented as absolute numbers (proportions). It is best to be consistent.
A comment on huge difference in the response rates across countries would be useful.
Discussion
The discussion is well written. Limitations and areas for future research are well captured in the manuscript. Is there any bias that could have made the results less reliable?
The manuscript is well written with good scientific and public health applications. The authors have done a good work.
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Reviewer #2: Yes: Benjamin Kagina
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