Application of the Theory of Planned Behavior in Predicting Delay in Two-Month Vaccination among Infants: A Cross-Sectional Study

Dorri khalilzadeh, Fatemeh; Peyman, Nooshin; Mosa Farkhani, Ehsan; Mohammadi, Maryam

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Application of the Theory of Planned Behavior in Predicting Delay in Two-Month Vaccination among Infants: A Cross-Sectional Study

Fatemeh Dorri khalilzadeh

, Nooshin Peyman

, Ehsan Mosa Farkhani

, Maryam Mohammadi ^*

Abstract: (11 Views)

Background and Objectives: Vaccination is one of the most effective public health interventions. However, delays in childhood vaccination remain a challenge for health systems. This study aimed to predict two-month vaccination delay among infants based on the constructs of the Theory of Planned Behavior (TPB) in Mashhad, Iran, in 2024.

Materials and Methods: This cross-sectional analytical study was conducted among 150 parents of infants who had experienced a delay of more than 10 days in receiving the two-month vaccination in Mashhad, Iran, in 2024. Participants were selected using a multistage sampling method with probability proportional to size from health centers. Data were collected using a researcher-developed questionnaire based on the TPB constructs and analyzed using descriptive statistics, Spearman’s correlation, and multiple linear regression in SPSS at a significance level of 0.05.

Results: Overall, 57.3% of the infants had a delay of more than 30 days in receiving their two-month vaccination. Significant positive correlations were observed between all TPB constructs and vaccination delay behavior (p<0.001). In the regression model, attitude (β=0.521) and subjective norms (β=0.331) were significant predictors of behavioral intention, whereas perceived behavioral control was the only construct that directly predicted vaccination delay behavior (β=0.260, p<0.001). The TPB constructs explained 20.6% of the variance in vaccination delay behavior (R²=0.206, Adjusted R²=0.181).

Conclusion: Educational interventions based on the Theory of Planned Behavior, with an emphasis on strengthening perceived behavioral control, enhancing self-efficacy, improving access, and reducing environmental barriers, may help reduce delays in childhood vaccination.

Open Access Policy: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

Keywords: Vaccination, Vaccination Delay, Infant, Theory of Planned Behavior

Type of Study: Research | Subject: Health Education & Health Promotion
Received: 2026/04/14 | Accepted: 2026/08/1

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