Assessing the Impact of Rotavirus Vaccination in Iranian Children Under Five: An Agent-Based Modelling Approach.

BACKGROUND AND AIMS: Rotavirus is a leading cause of severe diarrhoeal disease in young children worldwide. In 2024, Iran introduced the pentavalent oral vaccine Rotasiil® into its national immunization program. This study aimed to estimate its potential epidemiological impact using an agent-based modeling (ABM) approach.

METHODS

An ABM was developed in NetLogo 6.4.0 to simulate rotavirus transmission among children under five in urban and rural settings. Agents represented individual children with attributes such as age, mobility, and susceptibility. Transmission occurred through contact within defined spatial grids, with higher probabilities assigned to rural settings to reflect poorer sanitation. Disease progression included incubation, symptomatic period, temporary immunity, and rare mortality. Two vaccination conditions (vaccinated vs. unvaccinated) were simulated, assuming 98% coverage and 55% seroconversion, consistent with Rotasiil-Liquid trial data. Population turnover and births were incorporated. Each condition was run 1,000 times over one simulated year, and incidence rates and symptomatic days per child-year were calculated. Sensitivity analyses tested low- and high-incidence assumptions.

RESULTS

In urban settings, vaccination reduced incidence from 0.663 to 0.440 cases per child-year (- 33.6%) and disease days from 3.895 to 2.584 (- 33.7%; p < 0.001). In rural populations, incidence declined from 0.670 to 0.488 (- 27.2%) and disease days from 3.968 to 2.886 (- 27.3%; p < 0.001). Sensitivity analyses showed consistent reductions of 26%-33% across incidence levels. Epidemic curves demonstrated lower peak intensity and more stable dynamics with vaccination.

CONCLUSION

Rotasiil is expected to substantially reduce rotavirus burden in Iran, lowering incidence, symptomatic days, and epidemic peak size. These results support the inclusion of rotavirus vaccination as a key child health intervention, though continued post-introduction surveillance remains essential.