Japan vaccinated heavily during COVID-19. Why are so many unsure about vaccinating next time?

A nationwide survey reveals how disease severity, vaccine protection, trust, cost, and information sources could shape vaccination decisions when the next pandemic arrives.

Study: Vaccine acceptance in a future pandemic after COVID-19 and its decision drivers in Japan. Image Credit: Roman Samborskyi / Shutterstock

In a recent study accepted for publication in the journal npj Vaccines, researchers in Japan assessed vaccination intention in a hypothetical future pandemic, identified factors associated with vaccine hesitancy, and determined conditions that may increase willingness to vaccinate across population subgroups.

Background

More than 700 million cases of coronavirus disease 2019 (COVID-19) and over 7 million deaths had been reported by December 2025, highlighting the importance of vaccination. Vaccination reduced disease spread and severity during COVID-19, yet vaccine hesitancy remains a concern.

Before and during vaccine rollout, hesitancy was associated with concerns about technology, adverse reactions, and distrust of governments. In Japan, vaccination intentions increased during rollout as perceived infection risk, workplace programs, and surrounding uptake changed. However, evidence about willingness to vaccinate during a future pandemic remains limited, and population subgroups may prioritize different vaccination conditions. Further research is needed to understand these differences and support preparedness.

About the study

A nationwide internet survey, the Japan COVID-19 and Society Internet Survey (JACSIS), was conducted from December 2024 to January 2025 through Rakuten Insight, using a panel of approximately 2.2 million residents of Japan.

The survey enrolled 28,000 participants aged 15-84 years and covered demographic, socioeconomic, health, psychological, social, and infectious-disease factors.

Responses were excluded when completion took less than 10 minutes, an attention check was failed, all listed underlying diseases were reported, or household size exceeded 15.

Future vaccination intention was assessed using four response options after participants considered a pandemic in which an approved vaccine reduced the risk of death by more than 50%. Scenarios varied by case-fatality rate and duration of vaccine-induced immunity.

Participants were classified according to prior COVID-19 vaccination and future intention. Each explanatory variable was examined using logistic regression adjusted for age, sex, income, and educational attainment, while information-source variables were additionally adjusted for one another; ordinal logistic regression was used as a sensitivity analysis.

Twenty vaccination-related conditions were assessed, and unsupervised clustering using Gower’s distance and partitioning around medoids identified priority profiles. 

Analyses were conducted in R version 4.3.2, with 95% confidence intervals and P < 0.05 considered significant. Ethical approval was obtained from the relevant Japanese institutional committees, and participants provided informed consent online.

Study results

Of 28,000 participants, 25,082 valid responses remained after exclusions, representing an 89.6% valid response rate. Among them, 19,027 (75.9%) had received at least one dose of the COVID-19 vaccine. After excluding 505 people who had not been vaccinated because of medical reasons, 24,577 participants were included in the main analyses.

Assuming a pandemic with a case-fatality rate comparable to COVID-19 (0.1–2%), 53.1% (13,050/24,577) reported being willing to receive vaccination. Among people vaccinated during COVID-19, 35.8% (6,814/19,027) were classified as “Did–Won’t,” indicating previous vaccination but future hesitancy. Among those not vaccinated during COVID-19, 84.9% (4,713/5,550) were in the “Didn’t–Won’t” group.

Vaccination intention changed with the assumed pandemic and vaccine characteristics. Among COVID-19-vaccinated respondents, “Probably won’t” responses declined from 25.6% to 15.5% when the assumed case-fatality rate increased from 0.1–2% to more than 20%, and from 31.0% to 16.6% when vaccine protection increased from 2–3 months to lifelong.

Changes were smaller among COVID-19-unvaccinated respondents. “Definitely won’t” responses showed only modest movement toward vaccination under more severe or protective scenarios.

Lower vaccination intention was associated with being in one’s 20s to 40s, female sex, lower income, and lower educational attainment. More frequent contact with others, particularly older adults, and having a regular physician were associated with greater intention.

Cardiometabolic conditions, including diabetes, hypertension, and dyslipidemia, and mental disorders were significantly associated with vaccination intention.

Neither the occurrence nor the severity of previous COVID-19 vaccine adverse reactions was associated with future intention. Lower general anxiety and fear of COVID-19 were associated with greater hesitancy.

Greater communion orientation was associated with willingness, whereas stronger agency orientation was associated with avoidance.

Greater knowledge of infectious diseases and vaccines was associated with higher vaccination intention, while endorsement of vaccine-related misinformation or COVID-19 conspiracy beliefs was linked to greater hesitancy.

People who believed another pandemic would not occur within 100 years were also more hesitant. Government, healthcare professionals, medical experts, television, and newspaper information sources were associated with lower hesitancy, whereas obtaining information from friends, celebrities, video-sharing platforms, and social media was associated with lower vaccine acceptance after adjustment.

Across 20 conditions, free vaccination, clinical-trial evidence, and physician recommendations were consistently valued. Recommendations from the World Health Organization (WHO) and the Japanese government were more influential among willing groups, while domestic vaccine development or manufacture was relatively more important among hesitant groups.

Clustering identified eight priority profiles, of which cluster 1 comprised 47.3% of participants and had the highest proportion in the “Won’t” group. Other clusters differed in priorities, including domestic production, vaccine modality, convenience, accessibility, family influence, and professional guidance, as well as in characteristics such as infectious-disease knowledge and education.

Conclusions

The findings indicated that willingness to receive vaccination in a future pandemic was substantially lower than the observed COVID-19 vaccine uptake in Japan.

Hesitancy was associated with demographic, socioeconomic, psychological, informational, and social characteristics, and vaccination priorities differed across eight population clusters. Free vaccination and clinical trial evidence were consistently valued, whereas trust in authorities, domestic production, and convenience varied across groups. 

The findings support preparedness approaches that recognize differing concerns rather than relying on a single communication strategy. However, the authors cautioned that stated intention should not be interpreted as a prediction of actual future vaccine uptake because attitudes may change as information about disease severity, vaccine effectiveness and safety, and social recommendations emerges during a pandemic. 

As the survey was conducted in Japan and administered online, further longitudinal and multi-country research is needed to assess broader generalizability.