https://orcid.org/0000-0002-2948-4497
ABSTRACT
Influenza vaccination is necessary to reduce severe influenza complications, especially in immunocompromised people such as cancer patients. However, few studies have examined influenza vaccination uptake among adult Japanese patients with cancer; their attitudes toward vaccination, as well as factors related to vaccine hesitancy, are unclear. From September 1 to October 31, 2020, we disseminated a web-based questionnaire to patients with a history of cancer via snowball sampling through e-mails and social media of two Japanese cancer patients associations. A total of 163 surveys were completed. One hundred (61.3%) participants received an influenza vaccination in the 2019/2020 season, and the main reasons for vaccination were as follows: recommendation by medical professionals, positive awareness of vaccination through books or the internet, and provision of vaccination in the workplace. The main reasons for not receiving a vaccination were fear of adverse events, lack of concern about influenza infection, and lack of trust in vaccine effectiveness. In terms of the 2020/2021 season, 120 participants (73.6%) reported their intention to receive an influenza vaccination. Multiple regression analysis showed that significant factors for positive intention were the the treatment without chemotherapy (p = .009), vaccination history in the 2019/2020 season (p < .001), prior experience of influenza infection (p = .043), and the perception that influenza vaccination was more important due to the coronavirus disease pandemic (p = .050). This preliminary survey revealed a relatively modest influenza vaccine coverage among adult Japanese patients with cancer and identified several factors related to positive intention toward vaccination.
Introduction
Seasonal influenza epidemics cause 291,000–646,000 deaths annually worldwide.Citation1 Influenza can be a serious threat for immunocompromised cancer patients, not only because of the underlying disease but also because of its treatment. Such patients are more likely to have influenza complications, such as respiratory failure, which are exacerbated by bacterial and fungal superinfections. In fact, cancer patients with influenza infection have a three to five times higher risk of hospitalization and a 10 times higher risk of death after hospitalization compared to the general population.Citation2 Therefore, vaccination for cancer patients is widely recommended for the reduction of morbidity and mortality associated with influenza. For example, the 2013 Infectious Diseases Society of America guidelines state that cancer patients should receive an inactivated influenza vaccine three months after the completion of chemotherapy.Citation3 While a recent systematic review showed that the benefits of influenza vaccination for cancer patients outweigh the potential risks, the existing evidence is mostly observational, incomplete, and of low quality.Citation4
Japan has a super-aging society, with 28.7% of the population aged 65 years or older and at an increased risk of cancer in 2020. Influenza caused 3276 excess deaths in the 2018/2019 season among the 127 million citizens living in Japan.Citation5 Currently, several domestically manufactured inactivated influenza vaccines are commercially available. Under the immunization law, adults aged 65 years or older and those aged 60–64 years with severe disabilities (due to organ dysfunction or human immunodeficiency virus infection) are eligible to receive free seasonal influenza vaccinations.
However, most of those under 65 years of age are not eligible for free vaccination, even if they have a history of cancer.Citation6 As a result, the coverage rate of influenza vaccination among the Japanese population is less than 40% among adults aged under 65 years and 48.0% among those aged 65 years or older.Citation7,Citation8 In terms of the influenza vaccination rate among the elderly, Japan currently ranks 19th out of 32 Organization for Economic Co-operation and Development countries for which data are available.Citation8
As few studies have examined influenza vaccination uptake among Japanese adult cancer patients, their attitudes toward vaccination, as well as factors related to their vaccine hesitancy, are not fully known. Such information has become increasingly pertinent for the clinical management of cancer patients, especially during the coronavirus disease (COVID-19) pandemic. Notably, a prior study has shown that the COVID-19 vaccination acceptance is related to the acceptance of influenza vaccination.Citation9 In this study, we conducted a cross-sectional questionnaire survey among adult Japanese cancer patients to examine their uptake of the influenza vaccine in the 2019/2020 season, as well as their attitudes, relevant knowledge, and barriers to influenza vaccination in the coming 2020/2021 season.
Patients and methods
Participants and study settings
From September 1 to October 31, 2020, we disseminated a web-based questionnaire survey to patients with a history of cancer via snowball sampling. Patients were invited to participate in the survey through e-mails and social media of two Japanese cancer patients associations. Patients who consented to participate responded anonymously to the survey, which was only available in the Japanese language (see Supplementary Material 1 for the full text of questionnaires translated into English).
Data collection
The survey included questions belonging to three domains: relevant demographic information, influenza awareness, and attitudes toward influenza vaccination. The demographic information included the participant’s age and sex, type of cancer, type of treatment received, as well as attributes of the attending physicians (e.g., specialty and affiliations). Questions concerning influenza awareness pertained to trust (“Do you trust the effectiveness of the vaccine?”), necessity (“Do you think it is necessary to get vaccinated?”), recommendation (“Would you promote vaccination to others?”), and the influence of the COVID-19 pandemic (“Do you consider that vaccination is more important after the COVID-19 pandemic?”). In terms of attitudes toward influenza vaccination, participants were queried regarding the following topics: (1) whether they were vaccinated in the 2019/2020 season; (2) willingness to receive a vaccination in the coming 2020/2021 season; (3) change of views on vaccination after reading the explanation on the risk of influenza, which was provided in the survey; and (4) willingness to get vaccinated if subsidized by the government (for those under 65 years of age), which aimed to evaluate the influence of additional knowledge attainment and financial incentives.
Data analysis
The demographics of the participants and the results of the questionnaires were analyzed using descriptive statistics. Furthermore, a correlation analysis was performed between each of the sociodemographic variables (predictor variables, see Supplementary Material 2) and the participants’ willingness to get vaccinated in the coming 2020/2021 season (outcome variable). Variables that were significantly correlated with the outcome variable were entered as predictor variables in the multiple regression analysis. All analyses were performed using Stata MP 15.0 (LightStone Corp., Tokyo, Japan), SPSS (IBM Corp., New York, USA), and Microsoft Excel (Microsoft Corp., California, USA). The level of statistical significance was set at p < .05.
Ethical approval
The study protocol was approved by the Medical Governance Research Institute (approval number: MG2019-03).
Results
A total of 163 participants completed the survey. The median age was 56 years (range, 21–87 years), and 65 (39.9%) participants were male (). The numbers of participants with full-time and part-time jobs were 63 (38.7%) and 45 (27.6%), respectively. Forty-four (27.0%) participants lived with one family member, and 39 (23.9%) lived with two family members.
Table 1. Sociodemographic characteristics of participants
At the time of the survey, 89 (54.6%) participants had completed their cancer treatment; 74 (45.4%) were still under active treatment. The most frequent type of cancer was leukemia (n = 98, 60.1%), followed by breast cancer (n = 15, 9.2%), prostate cancer (n = 8, 4.9%), lymphoma (n = 8, 4.9%), and colorectal cancer (n = 8, 4.9%). Chemotherapy was the most frequent type of treatment (n = 106, 65.0%), followed by radiotherapy (n = 52, 31.9%), surgical excision (n = 47, 28.8%), and hematopoietic stem cell transplantation (n = 40, 24.5%). The majority of participants (n = 68, 41.7%) were treated in the hematology department; 24 (14.7%) and 12 (7.4%) participants were treated in the oncology and general internal medicine departments, respectively.
Over half of the participants (n = 100, 61.3%) had a vaccination history in the 2019/2020 season. The main reasons for receiving or not receiving a vaccination are shown in . Medical professional recommendation was the most frequent reason for receiving a vaccination (n = 29, 29.0%); followed by positive awareness of vaccination through books or the internet (n = 23, 23.0%) and provision of vaccination in the workplace (n = 17, 17.0%). Fear of adverse events was the most frequent reason for not receiving a vaccination (n = 19, 30.2%), followed by a lack of concern for the influenza infection (n = 14, 22.2%) and a lack of trust regarding vaccine efficacy (n = 8, 12.7%). In terms of vaccination frequency across age groups, 61.9% (83/134) of participants aged < 65 years and 58.6% (17/29) of participants aged ≥ 65 years had been vaccinated in the 2019/2020 season.
Table 2. Main reasons for receiving or not receiving influenza vaccination
In terms of participant attitudes toward vaccination, 120 (73.6%) reported their intention to receive an influenza vaccination in the 2020/2021 season. Supplementary Material 2 shows the results of the correlation analysis between the intention to receive an influenza vaccination and participant characteristics. The intention to receive a vaccination was significantly correlated with the following factors: chemotherapy (R = – 0.205); doctor’s recommendation (R = 0.221); vaccination history before 2019 (R = 0.405); vaccination in the 2019/2020 season (R = 0.668); trust in the efficacy of the vaccine (R = 0.538); prior experience of influenza infection (R = 0.177); perception that vaccination was necessary (R = 0.603); recommendation of vaccination to other people (R = 0.549); and perception that influenza vaccination was more important due to the COVID-19 pandemic (R = 0.524). These nine variables predicted 52.5% (adjusted R2) of the variance in the multiple regression analysis, thus indicating a large effect size ().Citation8 Multicollinearity was not a concern (variance inflation factor < 10). In the final model, three factors were significantly associated with the intention to receive a vaccination in the 2020/2021 season: chemotherapy (p < .01, B = – 2.281, 95% confidence interval [CI] 0.018–0.571); vaccination in the 2019/2020 season (p < .001, B = 0.364, 95% CI 4.212–102.819); and the perception that influenza vaccination was more important due to the COVID-19 pandemic (p < .05, B = 1.123, 95% CI 1.034–9.144).
Table 3. Multiple regression analysis, predicting the intention to receive influenza vaccination in the next season. Outcome variable: intention to receive influenza vaccine in the next season
Responses to questions pertaining to the influence of additional knowledge attainment and financial incentives are shown in . Among the 51 participants who did not receive a vaccination in the 2019/2020 season, 16 (31.3%) reported their intention to get vaccinated in the 2020/2021 season, even if they had to pay the mandatory vaccine fee. The number of participants reporting their intention to get vaccinated increased to 25 (49.0%) after reading a general explanation about the risk of influenza and were presented with a hypothetical scenario in which vaccines would be provided free of charge.
Table 4. The change of intention to receive influenza vaccination in the next season
Discussion
In this study, a questionnaire survey on influenza vaccination was conducted among adult cancer patients in Japan prior to the 2020/2021 season and during the COVID-19 pandemic. The results showed that only 61.3% of cancer patients had been vaccinated during the 2019/2020 season, despite the fact that vaccination was generally recommended. Although influenza vaccination was more strongly recommended than usual due to the COVID-19 pandemic, only 73.6% of participants intended to get vaccinated in the 2020/2021 season. This suggested that vaccine hesitancy is a significant problem in patients with cancer. In addition, several factors related to the willingness to get vaccinated were identified; these may be used to facilitate awareness campaigns aimed at increasing vaccination coverage.
Our study suggests that the influenza vaccination coverage among cancer patients in Japan is higher than that in the general population. The coverage rate in the previous season was 55.4% among patients on active treatment and 66.3% among those who had completed treatment. In contrast, the vaccination coverage rate among Japanese citizens has been estimated to be 45%, with higher rates among the elderly.Citation10 A previous study reported that 57% of elderly outpatients in Japan were vaccinated,Citation11 which is comparable to the rates observed in our study. A prior study conducted at a university hospital in France reported a vaccination rate of 47% among patients over 65 years of age, which was similar to that observed in our study; however, the vaccination rate (19.9%) among patients under 65 years of age was much lower.Citation12 Nevertheless, vaccination rates among cancer patients in Japan are less than ideal, particularly considering the potentially severe consequences of influenza infection in this medically compromised group.
In the present study, we identified three factors that were associated with vaccination intent in the 2020/2021 season; these included chemotherapy, vaccination in the previous season, and the perception that influenza vaccination was more important due to the COVID-19 pandemic. A previous study conducted among elderly outpatients in Japan reported that the following factors were related to vaccination: physician recommendation, advanced age, trust in vaccine efficacy, and low susceptibility to side effects.Citation11 A survey of patients undergoing cancer treatment in Israel found that past vaccinations, low-risk malignancy, and the country of birth were associated with vaccination.Citation13 While predictive factors may vary depending on the characteristics of the study population and the specific factors investigated in the questionnaire, it is reasonable to assume that a history of influenza vaccination is an important predictive factor that is likely common to the majority of studies. Furthermore, the COVID-19 pandemic has attracted widespread attention to new vaccine development among the general public, which is expected to have a positive influence on influenza vaccination. In order to increase the influenza vaccination coverage rate among cancer patients, it would be important to identify those without a prior vaccination history for targeted recommendations by healthcare providers. A previous study showed that a clear recommendation by the attending physician contributed to the acceptance of influenza vaccination.Citation14
As we found that a significant proportion of cancer patients exhibited vaccine hesitancy, scrutinizing the underlying reasons is crucial. One reason was the cost of vaccination, which can be several thousand Japanese yen (several ten US dollars). This cost is currently not covered in Japan for patients under 65 years of age. In our survey, 7.9% of participants attributed their vaccine hesitancy to the cost of the vaccine. However, an 18% increase in the number of participants intending to get vaccinated was observed after they read a general explanation about the risk of influenza and were presented with a hypothetical scenario in which vaccines would be provided free of charge. Therefore, extending current routine vaccination programs to include cancer patients under 65 years of age would further improve vaccine coverage. Other reasons for vaccine hesitancy included concerns regarding vaccine efficacy and adverse reactions. Indeed, among participants under 65 years of age, 15.9% exhibited vaccine hesitancy even if they were offered free vaccination; nevertheless, the vaccine coverage rates were approximately equivalent between the two age groups. As several participants had a history of adverse reactions after vaccination, it was inevitable that a small proportion would have vaccine hesitancy. Considering the increased risk of complications after influenza infection in cancer patients, more efforts should be made by healthcare providers in Japan to increase the vaccination coverage.
Limitations
Our study has several limitations. First, we used a snowball sampling method, as opposed to random sampling. As anyone can access the questionnaire form, it is possible that some answers may be provided by patients without cancer, thereby limiting the reliability of the results.
Second, the participants in the present study may have had an increased level of awareness and knowledge about influenza vaccination compared to general cancer patients, since a web-based survey was administered through cancer patients associations. These participants also likely had a higher level of health literacy and proficiency with internet technology, which may have positively influenced vaccination uptake. Furthermore, participants who were motivated to partake in the survey may also have been more inclined to receive the vaccine. Third, while the COVID-19 pandemic was associated with an increased willingness to receive the influenza vaccine, it must be acknowledged that this effect is likely to decrease once the pandemic is over. Fourth, as the number of participants was limited, further research is warranted to obtain findings more generalizable to other types of cancer. Fifth, this survey was primarily focused on the evaluation of attitudes toward vaccines. Future studies should utilize additional qualitative tools such as in-depth interviews for a detailed investigation of the psychological aspects of vaccination intent.
Conclusion
Our preliminary questionnaire survey on influenza vaccination revealed a relatively modest influenza vaccine coverage among adult Japanese patients with cancer and identified several factors that could be targeted for interventions aimed at increasing vaccination uptake in this vulnerable population.
Disclosure of potential conflicts of interest
KT received personal fees from Novartis Pharma, Japan, as a lecture reward outside the submitted work. EK received personal fees from Otsuka Pharmaceutical Co., Ltd. as a lecture reward outside the submitted work. MK received personal fees from SBI Biotech Co., Ltd. TT received personal fees from Medical Network Systems, MNES Inc., and Bionics Co., Ltd. All other authors declare no competing interests in this work. All interests have been disclosed fully to Taylor & Francis, and we have in place an approved plan for managing any potential conflicts arising from them.
Supplemental Material
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The authors thank Mr. Aida and Ms. Ohtani for their cooperation in recruiting the participants for this study.
Data availability statement
The data that support the findings of this study are available from the corresponding author, MK, upon reasonable request https://www.megri.or.jp/inquiry.
Supplementary material
Supplemental data for this article can be accessed on the publisher’s website at https://doi.org/10.1080/21645515.2021.1977569
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References
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