There were three major findings arising from our survey-based study. Firstly, we demonstrated that influenza vaccine coverage is suboptimal, does not differ depending on the type of allergen immunotherapy the patient is undergoing (inhaled allergens vs. insect venoms), and decreases after the beginning of allergen immunotherapy. Secondly, general vaccine coverage among adult patients undergoing AIT is not satisfactory. Finally, Polish doctors taking care of AIT patients are convinced about the safety and effectiveness of prophylactic vaccines in allergic patients undergoing AIT, but planning vaccination visits is problematic, as they lack clear recommendations addressing the time interval between the procedures.
4.1. Influenza Vaccine Coverage among Patients Undergoing AIT
The influenza vaccine is the best method of preventing this viral disease [
15], therefore it is recommended for all Polish citizens over six months of age due to epidemiological reasons, and it is particularly advised for patients over 55 years old or with chronic disorders, like asthma or diabetes [
2].
We have demonstrated that around 40% of patients undergoing AIT claim to have received at least a single influenza vaccine during adulthood before the beginning of AIT, which corresponds with findings from a Polish nationwide survey (32%) conducted in 2013 [
16]. These numbers are not satisfactory, as the influenza vaccine composition changes every year, thus a single vaccination is not sufficient—the vaccine is recommended for annual use. Among our patients, only around 20% declared being vaccinated against influenza more than once. Influenza vaccine hesitancy in the general population is connected with a belief about inadequate influenza vaccine effectiveness, the perceived low possibility of contracting influenza, and concerns about adverse events [
16,
17]. This topic has yet to be investigated among AIT patients.
According to data published by the ECDC (European Centre for Disease Prevention and Control), influenza vaccine uptake in the entire Polish population is lower than 4% (seasons 2015/2016 and 2016/2017) [
18]. Similar data were collected from Polish nationwide survey studies carried out in 2013 and 2016 which found that the declared influenza vaccination rate was approximately 6–7%, with another 6–7% of patients willing to get vaccinated later in the influenza season [
16,
17]. Observations made in 2015 on Polish patients suffering from chronic diseases suggest that influenza vaccination coverage may be higher (9–58%) depending on the patient’s medical condition (with the highest rate reported by patients with chronic pulmonary diseases) [
19].
The other problem is the noticeable decrease in the interest in influenza vaccines after the beginning of AIT (36% and 45% previous to, and 14% and 6% after the beginning of AIT, respectively). These results suggest that the regular administration of an allergen extract may impede the performing of prophylactic vaccinations against influenza. Furthermore, our results reveal that even less patients decided to get vaccinated against influenza during the ongoing COVID-19 pandemic (3–9%). These findings correlate with the survey conducted in November 2020 on the general population of Polish adults, which found that at that time only 5.5% of patients had already been vaccinated against influenza [
20]. It is alarming as to why influenza vaccine coverage is so low among Poles, while according to the recent (2020) State of Vaccine Confidence in the European Union and United Kingdom, as many as 78.1% and 82.4% of Polish respondents agree that the seasonal influenza vaccine is important and safe, respectively [
11].
Over 20% of our patients belong to the group at high risk of severe influenza and its complications because of their age or concomitant diseases, which makes them candidates for the annual influenza vaccine uptake. As it results from the outcomes of our survey, the past history of vaccinations against influenza in this special group of patients is not significantly higher than in general population.
The presented data regarding influenza vaccine coverage are still not satisfactory and much lower than recommended by different health organizations, for example the target of an annual 70% coverage for the population over six months of age (USA Healthy People 2030) [
21], or of 75% coverage of elderly patients (over 65 years old) in the European Region (WHO, ECDC) [
22,
23].
4.2. General Vaccine Coverage among Patients Undergoing AIT
According to the WHO, one of the ten threats to global health is vaccine hesitancy [
24]. It might seem that the problem concerns only some of the vaccinations that are mandatory for use in children (e.g., MMR vaccine). In fact, although the numbers may vary between countries and vaccine type, the general vaccine coverage among adult patients is low [
25,
26,
27].
In the group of our respondents, the highest vaccination coverage applies to tetanus and pertussis vaccines. This may result from the fact that in Poland these vaccines are recommended for all adult patients—a combined dTap vaccine every ten years starting at age 19, during every pregnancy and in all people who have or may have contact with infants. Additionally, the tetanus vaccine (with or without the pertussis component) should be considered in all patients after exposure to tetanus, depending on the history of tetanus vaccinations [
2]. Surprisingly, in one of our groups, 70% of patients declared being vaccinated against pertussis, although only 21% were vaccinated against tetanus. These results are probably overestimated regarding the pertussis vaccine or underestimated regarding the tetanus vaccine as the only vaccinations against pertussis registered in Poland are combined with diphtheria and tetanus toxoids. These unlikely results can indicate another problem, which is patients’ low awareness of their own vaccination history. One of the solutions to this issue could be offering adult patients vaccination booklets similar to those prepared for paediatric patients or the implementation of electronic vaccination tracking.
Pneumococcal infections in adults are connected with high mortality, particularly among the elderly, patients with chronic respiratory diseases (including asthma), diabetes mellitus, chronic heart disease and smokers [
28,
29]. According to the Polish vaccination schedule, the pneumococcal vaccine is recommended for all adult patients with various chronic disorders, impaired immune function and smokers [
2]. In our patients, the vaccination rate is low (5–7%), which may result from the relatively low mean of the age of the respondent population (38 years old).
Poland belongs to a tick-borne encephalitis (TBE) risk region (the “TBE belt”); however, the degree of endemicity varies depending on the part of the country [
30]. The Polish vaccination schedule recommends vaccination against TBE to all people in these endemic regions and who work or spend time outdoors (and therefore are at risk of a tick bite) [
2]. In our patients, the vaccination rate is lower than 5%. Survey studies from other “TBE belt” countries indicate higher vaccination coverage [
31].
Vaccines against COVID-19 are the hope for ending the COVID-19 pandemic. As these vaccines rely on new technologies (mRNA and viral vectors) and were introduced for public use relatively quickly, many patients have concerns regarding their safety and efficacy [
32,
33]. Among our respondents, around 50% were willing to get vaccinated against COVID-19 (the study was conducted before and at the beginning of COVID-19 mass vaccinations in Poland). We did not have the chance to verify if those respondents actually got vaccinated against COVID-19, but after a year of accessibility of different vaccines against COVID-19 in Poland, the number of fully vaccinated Polish citizens is approximately 59% (figures as of 22 February 2022) [
34].
Vaccine acceptance, including the COVID-19 vaccine, is crucial in guaranteeing herd immunity and in eliminating or decreasing the prevalence of infectious diseases [
35,
36]. Vaccine acceptance depends on many factors connected with the specific vaccine, the perception of a particular disease among the population and the general trust in science and the healthcare system [
35]. During the ongoing pandemic, many studies regarding attitudes towards COVID-19 vaccines have emerged. Similarly to other vaccinations, beliefs and concerns related to COVID-19 vaccines are connected with age, gender, residency, perceived risk of the disease, education level, income, life circumstances (pregnancy) or access to social media [
37,
38,
39,
40,
41,
42,
43]. For this reason, we want to underline the importance of adjusting the means of communication to individual needs, as such interventions are more effective than the ones addressed to the whole population. Since patients undergoing AIT are not homogenous in terms of demographic or economic factors, the message concerning the possibility and safety of vaccinations, including the COVID-19 vaccine, should be tailored to a particular patient.
It is worth noting that 55% of Polish respondents declare overall vaccine confidence (comparing to 37% in 2018) [
11]. On the contrary, among patients who responded to our questionnaire, different vaccines’ coverage is rather low. Unfortunately, there are no official data available for adult vaccination coverage in Poland, as all information regarding this topic derive from individual surveys, which are usually conducted on patients suffering from various chronic diseases or special groups of patients and not on the general public [
19,
44,
45]. Thus, it is hard to determine if low vaccine coverage among our respondents results only from the fact of undergoing AIT or the problem is a more complex one, especially if only individual patients declared having problems with getting vaccinations while undergoing AIT.
4.3. Doctors Attitude
Studies regarding vaccine hesitancy indicate the important role of doctors, especially general practitioners, on shaping patients’ attitudes about immunization. Fortunately, many patients still indicate that their doctors are the most trusted source of health information [
25,
44,
46]. This should prompt the doctors to update their knowledge and to provide the patients with information compliant with evidence-based medicine. On the other hand, some research points to limited knowledge about adult vaccinations among healthcare providers [
47,
48,
49].
The majority of doctors who took part in our questionnaire agreed on the safety and effectiveness of vaccinations among patients undergoing AIT (96% and 94%, respectively). Furthermore, over 80% of respondents recommend that their patience are vaccinated against influenza annually. Unfortunately, this does not lead to satisfactory vaccine coverage.
Our results correlate with the opinion on the lack of negative interference between vaccinations and AIT declared by 95% of AIT experts who took part in an international survey. The majority of doctors did not observe any alarming AIT (98%) or prophylactic vaccine (87%) adverse effects when combining these two procedures, and the only reported unfavourable reactions were local and mild [
50].
Various answers regarding the rules obeyed while planning the vaccination schedule in AIT patients and the opinion of more than 90% of doctors that clear recommendations concerning vaccinations among AIT patients are needed may indicate that doctors taking care of such patients are faced with a technical problem of arranging a proper vaccination date. More attention should be paid to simplifying the process of vaccinating patients undergoing AIT, and such recommendations should be prepared in the local language by local societies of allergology and vaccinology.
The problem of combining allergen immunotherapy and prophylactic vaccinations in adult patients has probably not been analysed yet, as we did not find any publications regarding this topic. Since there are no studies assessing both vaccine coverage in adult patients undergoing AIT and the attitude of physicians towards vaccinating such patients, we would like to emphasize the novelty and significance of our research. We hope that it will contribute to increasing the uptake of prophylactic vaccines among adult patients undergoing AIT, particularly those who are at risk of infectious diseases due to their age, concomitant diseases or place of residence. The group that would benefit the most from simplifying the vaccination process are certainly AIT patients themselves, however it would also improve protection in the general population due to herd immunity.