Effect of two vaccine doses in the SEIR epidemic model using a stochastic cellular automaton

TL;DR

This study extends the SEIR epidemic model with stochastic cellular automata to include two-dose vaccination strategies, analyzing different distribution scenarios and their impact on disease control and vaccine efficiency.

Contribution

It introduces a novel stochastic cellular automaton-based SEIR model with two-dose vaccination, evaluating various distribution strategies and their effects on epidemic outcomes.

Findings

Early vaccination can lead to disease-free equilibrium with fewer doses.

Fewer, well-timed doses reduce infections more effectively than many small doses.

Dose wastage increases with more applications and over time.

Abstract

In this work, to support decision making of immunisation strategies, we propose the inclusion of two vaccination doses in the SEIR model considering a stochastic cellular automaton. We analyse three different scenarios of vaccination: $i) unlimited doses, (ii) limited doses into susceptible individuals, and (iii) limited doses randomly distributed overall individuals. Our results suggest that the number of vaccinations and time to start the vaccination is more relevant than the vaccine efficacy, delay between the first and second doses, and delay between vaccinated groups. The scenario (i) shows that the solution can converge early to a disease-free equilibrium for a fraction of individuals vaccinated with the first dose. In the scenario (ii), few two vaccination doses divided into a small number of applications reduce the number of infected people more than into many applications. In addition, there is a low waste of doses for the first application and an increase of the waste in the second dose. The scenario (iii) presents an increase in the waste of doses from the first to second applications more than the scenario $(ii)$. In the scenario (iii), the total of wasted doses increases linearly with the number of applications. Furthermore, the number of effective doses in the application of consecutive groups decays exponentially overtime.