Associations between the prevalence of influenza vaccination and patient’s knowledge about antibiotics

Influenza is a highly infectious viral disease, presenting in one of three basic antigen types A, B or C. The virus can cause moderate to severe illness, with dangerous complications such as secondary bacterial pneumonia, myocarditis or worsening of existing chronic pulmonary or cardiopulmonary diseases [1]. The worldwide burden of influenza is estimated to include approximately one billion cases per year, with three to five million cases of severe illness, and 250,000 to 500,000 influenza-associated deaths [1]. Persons at highest risk are those aged 65 years and older and children under five years; however, influenza affects all age groups [2].

The new generation of influenza vaccines offers an option to protect individuals against influenza [3] but the prevalence of vaccinated persons differs highly within European countries: from 1 % of the elderly population in Estonia to 82 % in the Netherlands [4]. Among healthcare workers, vaccination rates varied from 12 % in Norway to 98 % in Romania in the 2008/2009 flu season [4‐7]. The reasons for this variety are manifold: first, official recommendations and funding schemes for flu vaccination differ [4]. Second, various misconceptions including that the influenza vaccination can cause the flu [8], or that upper respiratory symptoms occurring post-vaccination are indicative that the vaccine itself is ineffective, seem to account for much of the variation in vaccinations rates [8, 9]. A recent Cochrane report showed that while the effectiveness of the vaccine remains only modest, vaccination is correlated with a reduced risk of hospitalization for influenza or pneumonia, as well as for respiratory or cardiac diseases, and that there is ultimately reduction in all-cause mortality [10]. Therefore, immunization against influenza remains the most important public health goal to control seasonal, epidemic, and pandemic influenza [4, 6]. Increasing vaccination rates could be achieved by increasing the health literacy of the population regarding influenza and treatment options [7, 10‐13], thereby debunking myths about flu vaccination [13]. Moreover, many patients carry the incorrect assumption that antibiotics are effective against influenza [14, 15].

The current study aimed to identify associations between the knowledge about the spectrum of effectiveness of antibiotics, as well as patients’ and general practitioners’ (GPs) demographics and the probability of being vaccinated against seasonal influenza. The underlying hypothesis was that individuals with an understanding that antibiotics are ineffective against viruses, common colds, and flu were more likely to be vaccinated than persons without this knowledge.

Health literacy has been shown to have an impact on vaccination status [2, 9‐13], and inaccurate beliefs about antibiotics have been recognized [14, 15]. However, no prior study was found that addressed the association between a patient’s knowledge of the effectiveness spectrum of antibiotics and influenza vaccination status. Given the public health imperative to increase annual prevalence of influenza vaccination [21], understanding this educational gap can improve specificity in counseling by physicians and boost vaccination rates.

We identified an association between knowledge concerning the effectiveness spectrum of antibiotics and the probability of being vaccinated against influenza. Persons with a better knowledge had a significantly higher likelihood of being vaccinated in all regression models, with an OR of 1.35 in the fully adjusted model which was adjusted for patient and GP factors. Specifically, the two questions regarding the effectiveness spectrum of antibiotics showed a significant association with a positive vaccination status. The overall knowledge about antibiotics remains low in Austria [14, 15], as is the overall level of health literacy [22]. Less than one third of the Austrian population have been shown to recognize that antibiotics do not kill viruses, and this is also true for nearly half of those with tertiary education [15]. The reason that the adjusted results did not show an association between educational level and the seasonal influenza vaccination status could be due to a bias: educational status might be already included as a relevant factor in the antibiotics knowledge variable which has been shown as having an association with the educational level in a previous publication [15]. In the Additional file 1 it becomes obvious that tertiary educational level increased the likelihood of being vaccinated (crude model), however, this association vanished when including the antibiotic knowledge variable (adjusted models in Table 3). The European Health Literacy Survey, which has measured how people access, understand, appraise and apply information to make decisions in health care, showed that Austria ranked in the lower field regarding those literacy items [22]. It could be speculated that improvements in health literacy, particularly regarding the spectrum of antibiotic effectiveness, would result in an improvement in vaccination status. GPs could specifically address the topic of non-effectiveness of antibiotics for the treatment of the flu, or colds without superinfections, at the time of discussion of influenza vaccination. This clinical guidance could include debunking inaccuracies, such as the assumption that the influenza vaccination can cause flu or that it is not effective following a viral upper respiratory infection. Furthermore, professional counseling on the differences between bacterial and viral infections may encourage more patients to seek vaccination.

We identified the highest vaccination rates during the season 2009/2010 with 18.6 % of patients receiving the vaccine. In the season 2010/2011, the rate was only 14.0 %. This may be explained by the recruitment timeframe, which was between November 2010 and July 2011, meaning that patients recruited in November and December 2010 probably were not yet vaccinated. Another explanation could be the decrease in motivation to vaccinate after the flu pandemic in 2009 [23]. The overall low vaccination status is reflected by other studies, in which Austria has been described as one of the three Western European countries with the lowest rate of vaccinations [5, 24, 25]. In the most recent Austrian health literacy survey 2006/2007, about 20 % of participants indicated they were vaccinated against influenza [26]. Another explanation for the overall low influenza vaccination prevalence compared to other European countries could be the manner in which influenza vaccination is organized in Austria [4, 5]. Although influenza vaccination is officially recommended, vaccination remains voluntary and most Austrians have to pay for the vaccination out of their pocket. This is in contrast to, for example, the Netherlands, where elderly populations have funding for vaccination and the rate of vaccination is among 80 % [4].

Overall, older age, living in an urban area, and being a healthcare worker each demonstrated an increased likelihood of vaccination in our analysis. Among healthcare workers, the vaccination rate is higher than in the average sample, but with only 26.8 % in the season 2009/2010. This phenomenon has been observed elsewhere, as a recent Spanish study showed rates of healthcare workers approaching 31 %, and a decreasing trend after the year 2009 [23]. Another Spanish study showed that vaccination was higher in healthcare workers who recognized vaccination as effective and those worried about being infected or infecting patients leading to the assumption that improving health literacy even in healthcare workers could have a large effect in improving vaccination rates [27]. The vaccination rate in Austria, in contrast, was particularly low in kindergarten teachers. This result is concerning, as these persons can infect many children once they carry the virus [28]. However, the low numbers could also be a result of the smaller subgroup sample.

The highest prevalence of vaccination was observed in persons aged 65 years and older, with 35.1 % identified in the season 2009/2010. This result is promising as the elderly are a vulnerable group in relation to severe illnesses caused by the influenza virus; however, still far away from the goal of the 10^th World Health Assembly resolution [21]. Contrary to this, vaccination rates in persons under the age of 24 are very low, with only 8.4 % observed in the season 2009/2010.

The high variability of the vaccination status between the GP practices observed could lead to the assumption that personal engagement of the GP is more important than official recommendations. However, despite this variability, only a small correlation was found between vaccination status and the knowledge score between GP practices. Interestingly, female GPs had a higher likelihood to have vaccinated patients with an OR of 2.90, after adjustment for multiple patients’ demographic factors. The GP sample is small and, therefore, no generalizations could be drawn. Nevertheless, it is still noteworthy that similar results have been observed for other vaccines, such as varicella, where female GPs were found to be more likely to discuss immunization with recommended, non-funded vaccines [29], or HPV vaccination where female GPs in Australia had significantly higher rates of vaccinated patients [30].

The strengths of the present study were the large sample size and the similarity of the sample with the Austrian population with regard to sex, age and educational level [31]. However, there may still be some differences from the general population, because the sample groups were recruited from general practices. Another limitation is the fact that this study is cross-sectional and, therefore, of limited explanatory power. Furthermore, results are based on descriptive and self-reported survey data. In addition, the lack of a question regarding chronic conditions might have resulted in biasing the results, because chronic conditions are recognized as important predictors for being vaccinated against seasonal influenza [27, 32]. Furthermore, the division of the vaccination status variable in “yes” and “no/don’t know” did not consider those patients who probably were vaccinated but could not remember it anymore which could have led to an underestimation of patients vaccinated; however, the detailed analysis shown in the Additional file 2 shows that only few patients marked “don’t know”. In addition, it became obvious that, although patients that marked “don’t know” had a lower antibiotic knowledge score, these persons did not have a statistical effect on the overall regression model results presented in Table 3 (Additional files 2 and 3). Other limitations were the voluntary recruitment strategy of GPs and patients and the fact that the questionnaire was available only in German. It may be speculated that more GPs and patients interested in the topic of antibiotic resistance participated in the study, which might have over-estimated the real knowledge about antibiotics.

Austria, as well as many other European countries, still has the need for massive improvements in influenza vaccination rates. We observed that in any given flu season only as much as 18.6 %, and as little as 14 %, of the population were vaccinated. Recognizing the public health imperative to reduce the spread of flu and decrease potential complications, global strategies must be implemented to increase vaccination rates. The results of this study demonstrate that vaccination prevalence has associations with patient’s knowledge about the effectiveness spectrum of antibiotics. Those patients that had an increased understanding of antibiotic uses were more likely to be vaccinated against influenza. One strategy to improve rates of vaccination for influenza would be for physicians to specifically counsel patients concerning antibiotics, flu vaccination and misconceptions about respiratory infections at the time of suggested vaccination. Furthermore, public health and marketing efforts could supplement in-office strategies to improve this area of health literacy, including the funding of the vaccination for vulnerable groups.