Data collection
A total of 1,680 adult men aged 41–49 years who lived in seven rubella epidemic areas in Japan (Tokyo, Chiba, Kanagawa, Saitama, Aichi, Osaka, and Fukuoka) were recruited for this study from the registry of a web-based survey company (INTAGE Inc, Tokyo, Japan). In late March 2020, this survey company randomly selected persons from a list of 11,754 individuals and invited them to participate in the study. Those who agreed to participate were subsequently directed to complete an anonymous online questionnaire. Registrants were provided with financial incentives for their participation. Recruitment ended when the number of participants reached approximately 1,600 individuals.
Questionnaire
Demographic information
The survey questions included basic demographic information such as age, gender, marital status (married or unmarried), highest level of education completed (less than high school, college or vocational school, university or higher, or other/prefer not to answer), household income (< 5, 5–7.99, or ≥ 8 million Japanese yen/year, or do not know/prefer not to answer), number of children (≤ 1, or > 1), and occupation (employee/civil servant as a regular employee, manager, non-regular employee, or self-employed/other). Participants were also asked about their smoking status (never, current, or former smoker). To assess partner’s current desire for pregnancy, each participant was asked the following question: “Does your spouse (partner) currently have a desire to become pregnant?” with the response options of yes, no, and do not know. To determine the respondents’ vaccination behavior, they were asked, “Did you get vaccinated against influenza this season?” with the response options of yes, no, and do not know. We developed the original questionnaire in Japanese for this study. The English translated version of the questionnaire is available (see Additional file 1).
Outcomes
To determine the respondents’ rubella testing and vaccination history from February 2019 to March 2020 (i.e., fiscal year 2019), they were asked, “Did you receive a voucher for rubella antibody testing and vaccination from your residential local government?” (response options: yes, no, do not know), “Did you receive an antibody test for rubella using the voucher?” (response options: yes, no), and “Did you get a rubella vaccination using the voucher?” (response options: yes, no).
Awareness of rubella prevention
To assess the respondents’ understanding of the government recommendation regarding rubella vaccination for men of their generation, we asked, “Are you aware that it is recommended that men born from fiscal years 1962 to 1978 receive a rubella vaccination?” (response options: yes, no). To determine whether an individual’s rubella vaccination history could be confirmed, we asked, “At present, do you have access to your records such as the Maternal and Child Health Handbook (not including your parents’ recollection) to confirm whether or not you have previously been vaccinated against rubella?” (response options: yes, no). Each participant was also asked, “Do you have acquaintances who received a rubella antibody test from February 2019 to March 2020?” to determine whether the respondents’ acquaintances were tested for rubella antibodies in fiscal year 2019. The responses were categorized as none no or yes in the analysis.
The participants were also asked the following questions to measure their perceptions of the risks associated with a rubella outbreak: “Are you aware that men in your generation, born from fiscal years 1962 to 1978, had no opportunity to be vaccinated against rubella?” (response options: yes, no) and “Are you aware that babies carried by mothers who are infected with rubella may develop a serious condition called congenital rubella syndrome?” (response options: yes, no).
Statistical analysis
The proportions of the participants who received a rubella voucher, underwent rubella antibody testing, and were vaccinated against rubella in fiscal year 2019 and the 95% confidence intervals (CIs) were calculated by the assessed participant characteristics. Log binomial regression analyses were performed to explore the associations between participants’ awareness of the rubella prevention program and their history of rubella antibody testing in fiscal year 2019, adjusting for social background characteristics. All demographic variables (except for gender and age) and variables shown to be statistically significant (P < 0.05) in the univariate analyses were included in the primary model, and the variables that remained significant were then selected for the final model. Using a similar model, we also assessed receipt of a voucher for the rubella antibody testing and vaccination program as the dependent variable. All analyses were done with Stata/MP, Version 15.1 (College Station, TX, USA). Statistical tests were two-sided and regarded as statistically significant at P < 0.05.
Ethics statement
This study was approved by the ethical committee of the International University of Health and Welfare (19-Im-013).