https://orcid.org/0000-0002-9334-1423
ABSTRACT
Many factors are related to vaccination intentions. However, gender differences in the determinants of intention to get the coronavirus disease 2019 (COVID-19) vaccine have not been fully investigated. This study examined gender differences in the determinants of willingness to get the COVID-19 vaccine among the working-age population in Japan. We conducted a cross-sectional study of Japanese citizens aged 20–65 years using an online self-administered questionnaire in December 2020. Logistic regression analysis was performed. Among 27,036 participants (13,814 men and 13,222 women), the percentage who were willing to get the COVID-19 vaccine was lower among women than among men (33.0% vs. 41.8%). Age and education level showed a gender gap regarding the association with willingness to get the COVID-19 vaccine: men who were older or had a higher level of education were more willing to get the vaccine, whereas women aged 30–49 years and those with a higher level of education showed a relatively low willingness to get the vaccine. For both men and women, marriage, higher annual household income, underlying disease, current smoking, vaccination for influenza during the current season, and fear of COVID-19 transmission were linked to a higher likelihood of being willing to get the COVID-19 vaccine. These findings give important insight into identifying target groups in need of intervention regarding COVID-19 vaccination, especially among women. Providing education about COVID-19 and influenza vaccination in the workplace may be an effective strategy to increase COVID-19 vaccine uptake.
Introduction
Vaccines are expected to be a key measure against the coronavirus disease 2019 (COVID-19) pandemic.Citation1 Vaccine development usually takes decades, and, although a variety of COVID-19 vaccines are currently being developed at an unprecedented rate, evidence has not yet established their long-term safety.Citation2 In Japan, the COVID-19 vaccination program has been administered since February 2021, with eligibility proceeding in the following order: healthcare workers, older adults (aged 65 years or older), and people with underlying diseases and caregivers working at care facilities for older adults.Citation3 Other people will become eligible for vaccination at a later date, following the populations listed above, which are the main sources of infection.Citation4 To reach herd immunity, most citizens need to be vaccinated.Citation5
Vaccination intentions are recognized as the most important issue in the rollout of vaccination programs.Citation6 However, Japan is known for its lack of public trust in vaccinesCitation7 because negative campaigns against the vaccination – highlighting scandals and severe adverse effects, for instance – have increased hesitation concerning some vaccinations over the past several decades.Citation8–11 For example, a national human papillomavirus vaccination program for girls was launched in 2013 but was discontinued after 3 months because of sensational case reports of adverse effects.Citation12 This event had a negative impact on vaccination intentions, especially among women.Citation13
Various factors are related to COVID-19 vaccination intentions. Previous studies have reported that age, gender, race, education level, influenza vaccination status, and fear of COVID-19 transmission are associated with the willingness to get the COVID-19 vaccine.Citation14–18 In Japan, willingness to get the COVID-19 vaccine was previously examined in a single study of 1,100 adults, with results showing that vaccine hesitancy was higher in Japan than in other countries, particularly among women.Citation19 However, gender differences in the determinants of willingness to get the COVID-19 vaccine, such as demographic and health characteristics, influenza vaccination status, and fear of COVID-19 transmission, have not been fully investigated. Furthermore, more studies involving larger samples of the working-age population are needed. Therefore, the current study examined gender differences in the determinants of willingness to get the COVID-19 vaccine among the working-age population in Japan. This study will give important insight into identifying target groups in need of intervention regarding COVID-19 vaccination.
Materials and methods
Study design
We conducted a cross-sectional study about COVID-19 among the working-age population in Japan on December 22–26, 2020. The present article is part of a series of studies conducted under the CORoNaWork (Collaborative Online Research on the Novel-coronavirus and Work) Project.Citation20 This study was conducted during the third wave of the COVID-19 pandemic in Japan, when the number of infected people and deaths peaked.Citation21 Although COVID-19 vaccination began in December 2020 in the United Kingdom (UK) and the United States (US), Japan had not yet begun to administer COVID-19 vaccines during the survey period.Citation22 Pfizer requested a fast-track approval of its COVID-19 vaccine from the government of Japan on December 18, 2020 and became the first company to receive this approval on February 14, 2021.Citation3
Criteria for eligibility for the present study were being aged 20–65 years and currently working. Healthcare workers and caregivers were not invited to participate. We recruited study participants from the panelists of Cross Marketing Inc. (Tokyo, Japan), an Internet research company. These panelists regularly respond to self-administered Internet surveys distributed by the company, receiving tokens that can be redeemed for products and services as compensation.
For this survey, we used quota sampling by gender, residence (five districts), and occupation (office worker or other). Information on these characteristics was retrieved from the panelists’ Cross Marketing Inc. registration information. Cross Marketing Inc. sent an invitation e-mail to panelists who met the eligibility criteria, and those who were interested in the study proceeded to the survey via a hyperlink. The participants provided informed consent prior to beginning the online questionnaire. We set a quota of 1,650 participants for each of the 20 strata (n = 33,000) and ceased recruitment when the target number was reached. In total, 33,087 participants from all over Japan completed the questionnaire. After excluding invalid responses, a total of 27,036 participants remained (). All participants received standard incentives through Cross Marketing Inc. (i.e., a few dollars’ worth of tokens). The study was conducted according to the guidelines of the Declaration of Helsinki, and it was approved by the Ethics Committee of the University of Occupational and Environmental Health, Japan (Approval number: R2-079).
Figure 1. Flow chart of the study participants.
Measures
The survey questions included items on demographic and health characteristics, influenza vaccination status during the current season, fear of COVID-19 transmission, and willingness to get the COVID-19 vaccine. The demographic and health characteristics were gender, age, education, marital status, annual household income (1 USD was equal to 106.78 JPY, using 2020 conversion rates),Citation23 underlying disease, and smoking status. In line with a previous study,Citation18 we developed the following item to assess willingness to get the COVID-19 vaccine: “If a COVID-19 vaccine becomes available, I will get it.” The possible answers to this question were yes and no. Fear of COVID-19 transmission was assessed by asking “Do you fear COVID-19 transmission?,” with yes and no as the possible responses.
Data analysis
We calculated frequencies and proportions for all variables. Descriptive statistics were also calculated by gender to reveal more detailed background factors. Logistic regression analysis was performed to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for all variables to evaluate associations with willingness to get the COVID-19 vaccine. Because we hypothesized that gender was an important determinant in the current study, the analysis was stratified by gender. We adjusted for age; no adjustments were made for the other covariates because the purpose of this study was to detect target populations for future intervention programs. All P-values were two-sided, and statistical significance was set at P < .05. We used Stata/SE 16.1 (StataCorp, College Station, TX, USA) for all analyses.
Results
shows the characteristics of the study population. Data on a total of 27,036 participants (13,814 men and 13,222 women) were analyzed. We found that 43.0% of the participants reported that they had received the influenza vaccine during the current season. Regarding fear of COVID-19 transmission, 74.0% indicated that they felt fear. Overall, 37.5% of the participants expressed that they would like to get a COVID-19 vaccine if it becomes available.
Table 1. Characteristics of the study population
displays the characteristics of the study population by willingness to get the COVID-19 vaccine and gender. A total of 5,780 men (41.8%) and 4,367 women (33.0%) were willing to get the COVID-19 vaccine. Relatively high percentages of participants were willing to get the COVID-19 vaccine among those aged 60–65 years (men: 48.0%; women: 41.1%), those who had an underlying disease (men: 47.8%; women: 37.0%), those who felt fear of COVID-19 transmission (men: 49.5%; women: 37.0%), and those who had received the influenza vaccine during the current season (men: 59.2%; women: 43.7%). These percentages were higher in men than in women.
Table 2. Characteristics of the study population by willingness to get the COVID-19 vaccine and gender
presents the factors associated with willingness to get the COVID-19 vaccine by gender. Men aged 50–59 years (aOR: 1.38; 95% CI: 1.02–1.86) and those aged 60–65 years (aOR: 1.76; 95% CI: 1.30–2.40) were more willing to get the COVID-19 vaccine than were men aged 20–29 years. Conversely, women aged 30–39 years (aOR: 0.86; 95% CI: 0.76–0.97) and those aged 40–49 years (aOR: 0.80; 95% CI: 0.71–0.91) were less willing to get the vaccine than were women aged 20–29 years. Regarding education level, compared with having a junior high or high school education, having a university or graduate school education was a facilitating factor for willingness to get the COVID-19 vaccine for men (aOR: 1.13; 95% CI: 1.04–1.22) but a barrier for women (aOR: 0.83; 95% CI: 0.75–0.91).
Table 3. Factors associated with willingness to get the COVID-19 vaccine by gender
For both men and women, a significantly higher likelihood of willingness to get the COVID-19 vaccine was observed among those who were married (men – aOR: 1.37; 95% CI: 1.26–1.49; women – aOR: 1.30; 95% CI: 1.20–1.40), those with a higher annual household income (men – aOR: 1.91; 95% CI: 1.61–2.26; women – aOR: 1.32; 95% CI: 1.13–1.53), those with an underlying disease (men – aOR: 1.43; 95% CI: 1.34–1.54; women – aOR: 1.29; 95% CI: 1.19–1.39), those who currently smoked (men – aOR: 1.20; 95% CI: 1.11–1.30; women – aOR: 1.36; 95% CI: 1.24–1.51), those who had been vaccinated against influenza during the current season (men – aOR: 3.28; 95% CI: 3.05–3.52; women – aOR: 2.53; 95% CI: 2.35–2.73), and those with a fear of COVID-19 transmission (men – aOR: 3.09; 95% CI: 2.85–3.35; women – aOR: 2.54; 95% CI: 2.29–2.81).
Discussion
This study provides evidence on gender differences in the determinants of willingness to get the COVID-19 vaccine. In the present study, the percentage of people who were willing to get the COVID-19 vaccine was lower among women than among men (33.0% vs. 41.8%). Notably, we found a gender gap in the associations of age and education level with willingness to get the COVID-19 vaccine: men who were older or had a higher level of education were more willing to get the vaccine, whereas women aged 30–49 years and those with a higher level of education were less willing to get the vaccine. Other factors showed similar trends for men and women: for both men and women, a higher likelihood of being willing to get the COVID-19 vaccine was observed in married participants, those with a higher annual household income, those who had an underlying disease, those who currently smoked, those who had been vaccinated against influenza during the current season, and those with a fear of COVID-19 transmission. These findings give important insight into identifying target groups for improving COVID-19 vaccination intentions, especially among women.
In the present study, we found a gender difference in the willingness to receive the COVID-19 vaccine. This trend was similar to the findings of previous studies in developed countries.Citation14,Citation19,Citation24,Citation25 Women tend to be more proactive in preventive behaviors, but they are less willing to be vaccinated than men. Vaccination involves risks such as adverse reactions, and this sex difference can be attributed to evidence that women are more cautious about risks and take longer to make decisions.Citation26 Thus, there is an urgent need to plan and implement awareness campaigns aimed at increasing willingness among women to receive the COVID-19 vaccine.
The most notable finding of the present study was a gender gap in the associations of age and education with willingness to get the COVID-19 vaccine. As mentioned above, men who were older or had a higher level of education were more willing to get the vaccine, whereas women aged 30–49 years and those with a higher level of education were less willing to get the vaccine. For men, this finding is consistent with previous studies; older age and higher level of education are known facilitators for health protection, which should correlate with COVID-19 vaccination intentions.Citation24,Citation27,Citation28 Conversely, the current results for women vary from the findings presented in these studies. This difference may be explained by a higher level of concern about adverse effects of the vaccine among women aged 30–49 years and among those with a relatively high level of education in Japan during the current study period. We considered that recent reporting on adverse effects following receipt of the human papillomavirus vaccine in major Japanese newspapers may have had a negative impact on the vaccination intentions of these groups.Citation29 These findings may imply the need for intervention in this population regarding COVID-19 vaccination.
The current study found that influenza vaccination status and fear of COVID-19 transmission were strongly associated with willingness to get the COVID-19 vaccine among both men and women. These results are in line with previous studies.Citation16,Citation17,Citation30,Citation31 In the case of the 2009 influenza pandemic, perceived risk of infection translated into preventive behaviors, including vaccination.Citation32 Similarly, the experience of receiving a vaccine have been shown to increase an individual’s confidence in the efficacy and safety of other vaccines.Citation30,Citation31 Nevertheless, working-age people have fewer opportunities to receive the influenza vaccine compared with older adults because of the former group’s busy work schedules.Citation33 These findings suggest that providing education about COVID-19 and influenza vaccination in the workplace may be an effective strategy to increase COVID-19 vaccine uptake.
In the current study, a higher likelihood of being willing to get the COVID-19 vaccine was observed among those who were married, those with a higher annual household income, those with an underlying disease, and those who currently smoked. Vulnerable populations, such as people with low socioeconomic status, are often found to have relatively poor health and to need support regarding their willingness to be vaccinated.Citation16 In addition, a previous study on influenza vaccination suggests that single people are less willing to be vaccinated compared with their married counterparts because single people are not at risk of transmission from coresident family members.Citation11 Our finding regarding the presence of underlying disease may be related to the fear of COVID-19 transmission because underlying disease a known risk factor for clinical severity of COVID-19 infection.Citation24 Only our finding on tobacco use was inconsistent with previous studies, which have found that smokers often tend to refuse vaccines regardless of the risk of clinical worsening associated with smoking.Citation10,Citation11,Citation34 Further studies should focus on confirming the relationship between smoking and COVID-19 vaccination intention.
Overall, we found that 37.5% of the working-age population in Japan was willing to get the COVID-19 vaccine. This percentage is not high enough to achieve herd immunity through the vaccination program.Citation5 This acceptance rate is lower than that in other countries, such as China (91.3%), France (58.9%), the US (56.9%), and Russia (54.9%).Citation6 Furthermore, the acceptance rate is lower than the rate reported in a previous study in Japan (65.7%) that was conducted in September 2020.Citation19 One possible reason for the low vaccination intention in the current study may be tied to the research period.Citation15 Our study was conducted in December 2020, right after the start of the COVID-19 vaccination program in the UK and the US, and the media coverage of adverse effects was exaggerated.Citation35,Citation36 Another reason is that people of working age have been found to be less willing to get the COVID-19 vaccine compared with older adults,Citation19 which would affect the present results. These findings have important implications for vaccination intentions, although vaccination acceptance may change after the vaccine is available for administration among the working-age population.
The main strengths of this study are the large sample size and the use of a sample from throughout Japan. A limitation of this study is that we recruited study participants from an Internet research company’s list of panelists. A previous study on the anti-vaccine movement reported that anti-vaccine messages were more prevalent on the Internet than in other sources.Citation37 Therefore, the participants in the current study may have been particularly likely to access anti-vaccine websites, and this should be taken into account when interpreting the results of our study. Additionally, we conducted the current study before the administration of the COVID-19 vaccination program in Japan; therefore, we could not provide participants with detailed information, such as the vaccination schedule, which may have affected their willingness to get the vaccine.
In conclusion, the current study revealed a gender gap in the associations of age and education level with willingness to get the COVID-19 vaccine. In particular, women aged 30–49 years and those with a higher level of education were less willing to get the vaccine. These findings may imply the need for intervention for this population regarding COVID-19 vaccination. Providing education about COVID-19 and influenza vaccination in the workplace may be an effective strategy to increase COVID-19 vaccine uptake.
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
Acknowledgments
We thank the current members of the CORoNaWork Project (listed in alphabetical order): Professor Yoshihisa Fujino (present chairperson of the study group), Dr. Hajime Ando, Professor Hisashi Eguchi, Dr. Kazunori Ikegami, Dr. Tomohiro Ishimaru, Dr. Arisa Harada, Dr. Ayako Hino, Dr. Kyoko Kitagawa, Dr. Kosuke Mafune, Professor Shinya Matsuda, Dr. Ryutaro Matsugaki, Professor Koji Mori, Dr. Keiji Muramatsu, Dr. Masako Nagata, Dr. Tomohisa Nagata, Ms. Ning Liu, Professor Akira Ogami, Dr. Rie Tanaka, Dr. Seiishiro Tateishi, Dr. Kei Tokutsu and Professor Mayumi Tsuji. All members are affiliated with the University of Occupational and Environmental Health, Japan.
Additional information
Funding
References
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