Article Text

Original research
Association between social isolation and loneliness with COVID-19 vaccine uptake in Japan: a nationwide cross-sectional internet survey
  1. Tomohiko Ukai1,
  2. Takahiro Tabuchi2,3
  1. 1Epidemiology and Clinical Research, Japan Anti-Tuberculosis Association Research Institute of Tuberculosis, Kiyose, Tokyo, Japan
  2. 2Cancer Control Center, Osaka International Cancer Institute, Osaka, Japan
  3. 3Tokyo Foundation for Policy Research, Tokyo, Japan
  1. Correspondence to Dr Tomohiko Ukai; ukai_tomohiko{at}jata.or.jp

Abstract

Objectives We examined the association between social isolation and loneliness, increasingly recognised but neglected social determinants of health, with being unvaccinated against COVID-19.

Design This was a cross-sectional study.

Setting and participants A representative cohort of 22 756 individuals (aged 15–81 years) from the general Japanese population who responded to both the Japan COVID-19 and Society Internet Survey 2021 and Japan Society and New Tobacco Internet Survey 2022.

Primary and secondary outcome measures We calculated the ORs of remaining unvaccinated against COVID-19 in 2022, attributable to social isolation as assessed by the Lubben Social Network Scale, or loneliness as evaluated by the University of California, Los Angeles Loneliness Scale version 3. Reasons for abstaining from vaccination were solicited from the unvaccinated respondents. A multivariable logistic regression model was conducted with adjustments for demographic variables. Propensity score-matched comparisons were conducted as part of the sensitivity analysis.

Results Individuals with social isolation were more likely to be unvaccinated (OR 1.48, 95% CI 1.37 to 1.60), while individuals with loneliness were not (OR 0.96, 95% CI 0.88 to 1.05). Socially isolated individuals were significantly less likely to receive information from people who had been vaccinated (11% vs 15%) and less likely not to trust the vaccine approval process (19% vs 27%) compared with those who were not socially isolated.

Conclusions Despite not harbouring negative perceptions of the vaccine, socially isolated individuals exhibited lower rates of COVID-19 vaccination. Socially isolated individuals are important targets to reach to increase the number of vaccinated individuals.

  • COVID-19
  • EPIDEMIOLOGY
  • SOCIAL MEDICINE

Data availability statement

No data are available.

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STRENGTHS AND LIMITATIONS OF THIS STUDY

  • We prospectively examined the link between social isolation, loneliness and vaccine uptake in 22 756 Japanese participants.

  • Social isolation was measured using the Lubben Social Network Scale, and loneliness was assessed with the University of California, Los Angeles Loneliness Scale Version 3.

  • The odds of being unvaccinated were calculated using multivariable logistic regression, with propensity score serving as a sensitivity analysis.

  • The web-based sample may not reflect the general population’s demographics.

Introduction

Since the first novel COVID-19 case was observed in Wuhan, China, in 2019, countries around the world have been struggling to contain the virus.1 Vaccines are the most promising prophylaxis against COVID-19.2 However, many countries are currently lagging in their vaccination campaigns, and methods encouraging vaccination are being sought.

At the time of writing, in the USA and the UK, 33% and 25% of people, respectively, are still not vaccinated.3 In Japan, 80.4% of people have already been vaccinated twice; however, this has barely changed in the past 6 months. Social determinants of health, such as race, education and income, are related to being unvaccinated.4 It is important to consider these factors when making immunisation policies.

Social isolation and loneliness are important and neglected social determinants of health that have been recently raised by the WHO.5 Social isolation is the objective state of having a small network of kin and non-kin relationships and thus few or infrequent interactions with others.6 Meanwhile, loneliness is the painful subjective feeling that results from a discrepancy between desired and actual social connections.7 Social isolation and loneliness are associated with increased mortality, the development of cardiovascular disease, stroke, mental disorders and suicide.5 Why social isolation and loneliness increase mortality has not been fully explained; however, it is possible that people in these states do not take preventive measures against illness, such as not getting vaccinated.

Currently, the association between social isolation and loneliness with COVID-19 vaccination uptake has not been investigated. If socially isolated or lonely people are associated with low vaccine uptake, the causes of this association should be investigated, and measures should be taken. This population potentially comprises many unvaccinated persons which could be targeted to address the plateauing vaccination numbers. We, therefore, evaluate social isolation or loneliness and subsequent COVID-19 vaccination uptakes using a longitudinal study.

Method

This cross-sectional study used two-point longitudinal data obtained from the Japan COVID-19 and Society Internet Survey (JACSIS) in 2021 and the Japan Society and New Tobacco Internet Survey (JASTIS) in 2022.8 The JACSIS evaluated the health conditions and social determinants of the COVID-19 pandemic in Japan. The JASTIS evaluated the status of new tobacco products and sociodemographic factors among the Japanese general population. Both surveys were administered through internet questionnaires and longitudinally share the same respondents. JACSIS, the baseline survey in 2021, was distributed to 224 389 candidates registered as panellists at a Japanese internet research company (Rakuten Insight, Inc., Tokyo, Japan) between 28 July 2021 and 30 August 2021. We determined a sample size of 31 000 panellists based on Japan’s population distribution in 2019. The survey was terminated once the target number of respondents was reached for each category (sex, age and prefecture). Consequently, 31 000 panellists responded to the survey. To validate the quality of the data, we excluded responses with discrepancies and/or artificial/unnatural responses. The following criteria were used for exclusions: (1) an invalid response to ‘please choose the second alternative from the bottom’ (ie, panellists who failed to select the second from last alternative from the five options available); (2) positive responses to all questions related to drug use (eg, marijuana, cocaine or heroin) and (3) positive responses to all questions regarding 16 alternative underlying chronic diseases. We excluded 2825 respondents with discrepancies and/or artificial/unnatural responses (remaining respondents, n=28 175). In 2022, the JASTIS survey was distributed to participants from 8 February to 26 February. We used the same scheme as the JACSIS 2021 study. Consequently, 33 000 panellists responded to the survey and 30 130 remained after validation.

Further, 22 756 people, aged 15–81 years, responded to both surveys, and we used this cohort for the analysis (figure 1). The adjustment for non-responders is described below.

Figure 1

Participant flow chart.

The internet survey agency respected the Act on the Protection of Personal Information in Japan. A credit point system known as ‘E-points’, which could be used for internet shopping and cash conversion, was offered as an incentive. E-points were directly credited to participants’ accounts by Rakuten Insight.

Patient and public involvement

Patients or the public were not involved in the design, or conduct, or reporting, or dissemination plans of our study.

Measures

Social isolation and loneliness

Social isolation and loneliness were measured with the JACSIS 2021. Social isolation refers to the absence of relationships with other people.9 To measure social isolation, we used the Lubben Social Network Scale (LSNS-6).10 The validity and reliability of the Japanese version of the LSNS-6 were confirmed.11 The scale was developed to screen for social isolation among community-dwelling adult populations. The scale’s score ranges between 0 and 30, with a higher score indicating more social engagement. A score of 0–11 was regarded as social isolation.10

The University of California, Los Angeles (UCLA) Loneliness Scale version 3, Short Form 3-item (UCLA-LS3-SF3) was used to assess loneliness.12 13 The three items are in the past 30 days, how often have you felt (1) a lack of companionship, (2) left out and (3) isolated. The validity and reliability of the Japanese version of the UCLA-LS3-SF3 were confirmed.14 Participants responded to each item on a four-point scale (‘never’=0, ‘rarely’=1, ‘sometimes’=2 or ‘always’=3). The score range was 0–9, with higher scores indicating severe loneliness. A score from 4 to 9 was defined as loneliness.15

Vaccination status

In the JASTIS 2022 study, participants were asked about their vaccine status in February 2022. Participants who had not taken any vaccination at that point were categorised as unvaccinated. Participants who had been vaccinated at least once were categorised as vaccinated. Those who wanted to get vaccinated but could not owing to allergy were excluded.

Covariates

Based on a previous study16 and theoretical considerations, the following variables were included as covariates: age, sex (woman/man), marital status (married or not), education, annual household income, working conditions, living area (category), self-rated health, histories of hypertension, diabetes, hypercholesterolaemia, stroke, coronary heart disease, chronic obstructive pulmonary disease, cancer, and/or depression (yes or no), divorced (yes or no), widowed (yes or no), and living alone (yes or no). Covariates were measured in the JACSIS 2021.

Statistical analysis

Internet studies’ respondents are generally not representative of the general population; thus, we performed statistical adjustment to account for bias. Harmonisation of the data with a major national and representative cross-sectional study would allow us to pool data, providing the potential capacity to adjust for ‘being a respondent in an internet survey’. Since this method cannot completely adjust for the difference in respondents between an internet survey and a nationwide representative survey, the problem of generalisability remains. However, this method can approximate our estimate to a nationally representative estimate, using inverse probability weighting to account for baseline characteristics, such as sociodemographic and health-related factors.8 Details regarding this method have been given in previous reports.17

The response rate in the follow-up survey was problematic as non-responders differed in several ways from responders in the survey. There was evidence suggesting that attrition was higher among the younger and socioeconomically disadvantaged populations. Therefore, to account for potential non-random non-responses, an additional adjustment for ‘non-response in the follow-up survey’ was conducted, giving inverse probability weighting to the remaining participants in each survey by modelling the probability of not dropping out.18

The mean values and prevalence of the selected factors were calculated based on social isolation or loneliness, and the overall difference across groups was tested using a χ2 test.

We examined the association between social isolation and/or loneliness and being unvaccinated in 2022. Univariate ORs and 95% CIs of social isolation and loneliness for those being unvaccinated in 2022 were calculated using logistic regression analysis. In a multivariable-adjusted analysis, the model was adjusted for the following variables: age, sex, marital status, education, annual household income, working conditions, living area, self-rated health, history of chronic conditions, being divorced, being widowed and living alone. The association between social isolation and loneliness was not strong (correlation coefficient=0.19); thus, we added both variables to the multivariable logistic regression analysis. We tested statistical interactions for sex and age by adding a cross-product term for social isolation and/or loneliness to the model. The analysis revealed a significant interaction between loneliness and age; thus, we performed a subgroup analysis.

Propensity score matching

Depending on whether participants were socially isolated, lonely or equally scattered, we conducted Propensity Score (PS) analyses, as sensitivity analyses, to evaluate associations with being unvaccinated. Participants’ characteristics differed according to social isolation or loneliness (online supplemental table S1). PS weightings were used to account for the differences. PS (the probability of being socially isolated or lonely for each participant ranging from 0 to 1) was calculated through multivariable logistic regression analysis using factoring in potential confounders.19 To judge the success of each PS weighting in terms of creating groups that looked similar based on the observed covariates, we used standardised differences, those being the difference in proportions between the exposed and counterpart groups divided by the SD in the exposed group.20 Generally, a standardised difference of 0.1 indicates a potentially meaningful imbalance. When PS weighing creates an acceptable balanced univariate logistic regression analysis it can be used for the result.

Additionally, we compared the answers of socially isolated and not socially isolated unvaccinated participants, and lonely and not lonely unvaccinated participants, to identify the reasons why they choose to remain unvaccinated. A χ2 test was performed to reveal any significant differences between the groups.

For validation, p values were obtained using a two-tailed test, and a p<0.05 was regarded as significant. We used SAS V.9.4 (SAS Institute) for all statistical analyses.

Results

Of the 22 756 respondents to both the JACSIS 2021 and JASTIS 2022, 13 063 were categorised as socially isolated on the LSNS-6 and 8415 were categorised as lonely on the UCLA-LS-SF3 (table 1). Socially isolated individuals were mostly characterised by being aged 30–69 years, male, unemployed, having low self-rated health, living alone, never married and having a history of depression. Loneliness was more common among girls/women aged 15–49 years with low educational status, no income, low self-rated health, living alone, never married and a history of depression. Among 13 063 participants with social isolation, 1653 (12.7%) were not vaccinated. Among 9693 participants without social isolation, 804 (8.3%) were not vaccinated. Among 8415 participants with loneliness, 1020 (12.1%) were not vaccinated. Among 14 341 without loneliness, 1437 (10.2%) were not vaccinated. In the multivariable logistic regression analysis, the OR (95% CI) of being unvaccinated for those who were socially isolated was 1.48 (95% CI 1.37 to 1.60; table 2). There was no significant difference between lonely and not lonely people regarding being unvaccinated (0.96 (95% CI 0.88 to 1.05)). The results did not differ when using PS matching (online supplemental tables S1 and S2). As shown in online supplemental table S3), the ORs for unvaccinated lonely people were significantly higher only among participants aged ≥65 (1.62 (95% CI 1.25 to 2.01)).

Table 1

Basic characteristics of participants (N=22 756) with/without social isolation and with/without loneliness

Table 2

ORs of being not vaccinated against COVID-19 among participants with social isolation and with loneliness

When socially isolated and not socially isolated unvaccinated participants were asked why they were not vaccinated, the socially isolated group was less likely to be informed of vaccination by someone who was vaccinated (11% vs 15%, p=0.01), less likely to be advised to get vaccinated by family or a friend (2% vs 4%, p=0.02), less likely to distrust the vaccine approval process (19% vs 27%, p<0.01) and less likely to think the risk of their condition becoming serious was low (6% vs 9%, p<0.01). When lonely and not lonely unvaccinated participants were asked why they were not vaccinated, the lonely group was more likely to be afraid of experiencing an adverse reaction (58% vs 45%, p<0.01), worried about a short-term reaction (27% vs 22%, p<0.01), and worried about dying owing to the vaccine (21% vs 17%, p<0.01). In contrast to socially isolated participants, lonely participants were more likely to be advised by people who had already taken vaccination, be it their family or their friends (table 3).

Table 3

Answers to a questionnaire asking the reason for no vaccination from participants without vaccination in 2022

Discussion

This cross-sectional study found that social isolation was associated with an increased risk of not being vaccinated for COVID-19. Contrastingly, loneliness was not associated with a lower vaccination rate; however, the odds of being unvaccinated tended to be higher in those aged ≥65 years. Our findings show that socially isolated participants tended not to have information from those who had already been vaccinated (eg, relatives). Socially isolated unvaccinated participants did not have a particularly negative impression of the COVID-19 vaccine and were in fact less sceptical about the COVID-19 vaccine approval process. However, they were less confident about their health outcomes once they acquired COVID-19. Therefore, it is possible that this group would take COVID-19 vaccinations if they are appropriately reached. With vaccination rates coming to a head, how we approach these groups and give them accurate information about the vaccine is a public health challenge.

There is not much previous research in this area. In a cross-sectional study looking at the relationship between influenza vaccine uptake and the De Jong Gierveld Loneliness scale in 970 older adults in Germany,16 lonely participants were less frequently vaccinated against influenza (OR 0.71, 95% CI 0.51 to 0.97) than were their counterparts. Our results are consistent with a trend in which loneliness tended to be associated with not being vaccinated for COVID-19 when only older adults were observed.

Participants who were socially isolated were significantly more unlikely to be vaccinated compared with participants who were not socially isolated. This was not the case for lonely participants. Loneliness is a subjective feeling regarding the gap between a person’s desired levels of social contact and their actual level of social contact. Therefore, lonely people can be more interested in their surroundings and could collect information about vaccinations through media. Contrastingly, socially isolated people could intentionally avoid interaction with others and are often uninterested in external information. Socially isolated people have a weaker sense of civic responsibility and are less likely to vaccinate.21 Our results showed that socially isolated people did not receive information regarding vaccinations whereas lonely people collected information but were afraid of adverse events. We assumed that these differences between social isolation and loneliness explain the results.

The proportion of socially isolated participants was very high at 57%. This is almost the same as the 56% in a survey conducted among Japanese people in May 2020, which revealed an increase in social isolation owing to the COVID-19 pandemic.22 If socially isolated people took COVID-19 vaccination to the same level as people who are not socially isolated, 3.1 million [(Japan population)×(prevalence of social isolation)×(prevalence of unvaccinated among social isolation–prevalence of unvaccinated among total population)] unvaccinated people would take COVID-19 vaccination. The emergence of COVID-19 and subsequent countermeasures significantly increased the number of socially isolated people.23 Since social isolation is associated not only with being unvaccinated but also with mortality, socially isolated people must be identified and connected. Further, interventions and strategies must be explored at the individual, relationship, communal and societal levels.23 Although some countries such as the UK,24 Japan,25 and the USA26 considered social isolation public health issue, global coalitions should be formed to increase the political prioritisation of social isolation.

Until now, it has been assumed that socially isolated and lonely people have high levels of mortality; however, the cause of this increased mortality has not been clearly understood.5 The fact that the odds of being unvaccinated were higher among those who were socially isolated suggests that they could have increased mortality because they do not take preventive healthcare measures, such as getting vaccinated.

Limitations

There are some limitations to our study. First, since we used a sample collected from a web-based survey, the sample did not reflect the demographic distribution of the general population. To adjust for potential bias in the demographic distribution of the collected sample, we used sampling weights using an external, nationally representative database. However, there could still be residual bias. For example, since this study used a web-based survey, those familiar with the internet and social networking services would have been more likely to participate in the survey, which possibly leads to an underestimated prevalence of social isolation. Second, although we adjusted for the possible confounders found in previous studies, there could still have been residual confounders. Since there are not enough studies in this field, more research is needed.

Conclusions

Social isolation is associated with low COVID-19 vaccination uptake. However, socially isolated people do not have a negative impression of COVID-19 vaccination. Unvaccinated socially isolated people are important targets to reach and effectively mobilising them to vaccinate could lead to three million more people being vaccinated.

Data availability statement

No data are available.

Ethics statements

Patient consent for publication

Ethics approval

This study was reviewed and approved by the Research Ethics Committee of Osaka International Cancer Institute (approved on 19 June 2020; approval number: 20084). Web-based informed consent was obtained from all participants before they responded to the questionnaire, and the option to opt-out at any point was provided. Both parental consent and child assent were obtained for the participation of minors.

Acknowledgments

We thank Editage (http://www.editage.com) for English language editing.

References

Supplementary materials

Footnotes

  • Twitter @TakahiroTabuchi

  • Contributors TU contributed to the design of the study, analysis and interpretation of data, drafting the article and final approval of the version to be submitted. TT contributed to the conception of the study, acquisition of data, revising the draft critically for important intellectual content, and final approval of the version to be submitted. TT also serves as the guarantor of this work.

  • Funding TT was supported by Health Labour Sciences Research Grants (20FA1005, 19FA0501, 19FA2001 and 19FA1011; https://mhlw-grants.niph.go.jp/), Japan Society for the Promotion of Science (JSPS) KAKENHI Grants (18H03062, 21H04856; https://www.jsps.go.jp/english/e-grants/) and JST RISTEX grants (JPMJRX21K6).

  • Disclaimer The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.