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Observational Study
. 2024 Feb 29:12:1348170.
doi: 10.3389/fpubh.2024.1348170. eCollection 2024.

Predictive factors of coronavirus disease (COVID-19) vaccination series completion: a one-year longitudinal web-based observational study in Japan

Takaomi Kobayashi  1 , Mikiko Tokiya  2 , Akiko Matsumoto  2 , Takashi Nakano  3 , Yoshio Hirota  4 , Megumi Hara  1
Affiliations
Observational Study

Predictive factors of coronavirus disease (COVID-19) vaccination series completion: a one-year longitudinal web-based observational study in Japan

Takaomi Kobayashi et al. Front Public Health. .

Abstract

Introduction: Addresing vaccine hesitancy is considered an important goal in management of the COVID-19 pandemic. We sought to understand what factors influenced people, especially those initially hesitant, to receive two or more vaccine doses within a year of the vaccine's release.

Methods: We conducted longitudinal Web-based observational studies of 3,870 individuals. The surveys were conducted at four different time points: January 2021, June 2021, September 2021, and December 2021. In the baseline survey (January 2021), we assessed vaccination intention (i.e., "strongly agree" or "agree" [acceptance], "neutral" [not sure], and "disagree" or "strongly disagree" [hesitance]), and assumptions about coronavirus disease (COVID-19), COVID-19 vaccine, COVID-19-related health preventive behavior, and COVID-19 vaccine reliability. In subsequent surveys (December 2021), we assessed vaccination completion (i.e., ≥2 vaccinations). To investigate the relationship between predictors of COVID-19 vaccination completion, a multivariable logistic regression model was applied. Adjusted odds ratios (AORs) and 95% confidence intervals (CIs) were calculated while adjusting for gender, age, marital status, presence of children, household income category, and presence of diseases under treatment. In a stratified analysis, predictors were determined based on vaccination intention.

Results: Approximately 96, 87, and 72% of those who demonstrated acceptance, were not sure, or hesitated had been vaccinated after 1 year, respectively. Overall, significant factors associated with COVID-19 vaccine compliance included the influence of others close to the index participant (social norms) (AOR, 1.80; 95% CI, 1.56-2.08; p < 0.001), vaccine confidence (AOR, 1.39; 95% CI, 1.18-1.64; p < 0.001) and structural constraints (no time, inconvenient location of medical institutions, and other related factors) (AOR, 0.80; 95% CI, 0.70-0.91; p = 0.001). In the group of individuals classified as hesitant, significant factors associated with COVID-19 vaccine compliance included social norms (AOR, 2.43; 95% CI, 1.83-3.22; p < 0.001), confidence (AOR, 1.44; 95% CI, 1.10-1.88; p = 0.008), and knowledge (AOR, 0.69; 95% CI, 0.53-0.88; p = 0.003).

Discussion: We found that dissemination of accurate information about vaccines and a reduction in structural barriers to the extent possible enhanced vaccination rates. Once the need for vaccination becomes widespread, it becomes a social norm, and further improvements in these rates can then be anticipated. Our findings may help enhance vaccine uptake in the future.

Keywords: COVID-19; completion; hesitant; predictor; social norms; vaccination.

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Conflict of interest statement

TN receives lecture fees from Daiichi Sankyo Co., Ltd., Sanofi Co., Ltd., and Mitsubishi Tanabe Pharma Corporation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flowchart of the study, including daily count of COVID-19-positive cases and total vaccinations.
Figure 2
Figure 2
Percentage of participants receiving two or more vaccinations stratified by vaccination intention in January.
See this image and copyright information in PMC

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