This study aimed to determine the current status of influenza vaccination uptake in a working population (20–69 years) in Japan, and reasons for this population receiving or not receiving the vaccine. Overall, the most frequent reasons for receiving the vaccine were the desire to avoid infection with the influenza virus, and the desire to prevent symptoms becoming serious if already infected with the virus. The primary reasons for not receiving the vaccine included no time to visit a medical institution, the belief of being unlikely to become infected with influenza, and the inability to afford the vaccine, although there were variations in reasons according to sex and age.
Prevention of the onset of influenza and preventing influenza symptoms from becoming serious were the two major reasons given by individuals who received influenza vaccination. The influenza vaccine provides modest protection against the onset of influenza, with the efficacy rate reportedly being 51-67% in individuals aged 18–65 years . Furthermore, 33 healthy adults need to be vaccinated to avoid one incurring influenza symptoms . Twenty one percent of respondents chose “Lack of confidence that influenza vaccinations are effective” as a reason not to be vaccinated. They may be rightly critical of vaccine efficacy because of possible mismatching between circulating virus strains and the strains in the vaccine itself. The limitations of vaccine efficacy should be communicated to the general public, to maintain realistic expectations of the vaccine  .
The reasons for receiving influenza vaccination varied according to sex and age. Among those aged 30–39 years, a substantial proportion reported that they were vaccinated because they were living with family members at high risk of influenza becoming serious, such as children, the elderly, or pregnant women. Maternal influenza immunization is a strategy with substantial benefits for both mothers and infants , reflecting the fact that people aged 30–39 are commonly rearing children. Among those aged 20–29 years, a relatively higher proportion cited recommendations from family, friends, or acquaintances as the reason for accepting the influenza vaccine. These results suggest that educational messages should aim to address a wide range of possible concerns, and to improve targeted outreach to specific groups of workers.
The reasons for not receiving influenza vaccination also varied according to sex and age group. Among men aged 20–59 years, the most frequent reason for not receiving the vaccine was lack of time to visit a medical institution. A lack of time has also been cited as a major reason for healthcare workers not receiving the influenza vaccine . There appear to be various misconceptions that stop people from perceiving vaccination as an important measure and one that deserves priority over other matters in their daily lives. There have been some measures that can ensure access to vaccination such as providing vaccination in pharmacies , and an incentive for vaccination, an intensified advertising campaign, and offering a choice of influenza vaccines can improve vaccination rates in the workplace . Among men aged 60–69 years, the main reasons for not being vaccinated were the belief that they would not be infected with the influenza virus and that the disease would not become severe. In Japan, influenza vaccination is recommended for people 65 years of age or older, and some local governments are providing financial support for vaccination . Although men aged 60–69 may believe that they will not be infected or become seriously ill with influenza based on their experience, they should be given accurate information about the risk of infection, which increases with age.
The reasons for not receiving influenza vaccination varied more widely according to age among women than among men. The most frequent reason for not being vaccinated was lack of time to visit a medical institution in women aged 20–29, not being able to afford vaccination in those aged 30-49, concerns about adverse reactions in those aged 50–59, and doubts about vaccine efficacy in those aged 60–69. The avoidance of influenza vaccination among women aged 50–69 may be attributable to unfavorable views related to changes in influenza vaccination policy as a result of severe side effects and lawsuit judgments for compensation at the time their children were vaccinated . If these women retain negative impressions of influenza vaccination after reaching the age of 65 when vaccination is recommended, it may be difficult to increase the influenza vaccination rate in this age group.
This study was limited because all study participants were internet users, thus its generalizability to the wider population in Japan may be restricted. It is possible that there are differences in educational status and income between internet users and non-users. In particular, internet users aged 60 or older may be better at assimilating information than are the general population. Another limitation is that because each individual chose multiple choices for questionnaire responses, and choices were not independent, we were not able to apply chi-square analysis or other statistical analysis to determine the differences according to sex and age.