Estimating the Public Health Impact of MERS-CoV Vaccination in Thailand: A Simulation-Based Approach

Abstract

Objectives: Middle East Respiratory Syndrome coronavirus (MERS-CoV) remains a public health concern for Thailand, because of the risk of importation from Thai pilgrims attending the Hajj. With MERS-CoV vaccines under development, evidence on their potential impact is needed for vaccination planning. This study aimed to estimate the potential public health impact of MERS-CoV vaccination among Thai pilgrims attending the Hajj under different vaccine effectiveness (VE) and transmission scenarios. Methods: A compartmental model simulated MERS-CoV transmission among Thai and non-Thai pilgrims attending the Hajj over 30 days. Vaccination was applied only to Thai pilgrims before travel. VE scenarios of 30%, 50%, 70%, and 90% were compared with no vaccination across basic reproduction number (R0) values of 1, 2, 4, 6, and 8. Outcomes included infection burden and transmission dynamics, severe cases, deaths, and timing of case occurrence. Results: Increasing VE reduced the projected number of infections, severe cases, and deaths across all transmission scenarios. Without vaccination, cumulative infections among Thai pilgrims increased from 0.35 cases at R0=1 to 60.69 cases at R0=8. At R₀=8, cumulative incident cases over the 30-day simulation period decreased from 60.69 without vaccination to 6.05 with 90% VE. During the 30-day simulation, the maximum observed daily incidence decreased from 10.15 to 1.01 cases, and the maximum observed prevalence decreased from 33.65 to 3.36 cases. Cumulative severe cases decreased from 15.43 to 1.54 and deaths from 5.66 to 0.57. Vaccination also delayed prevalent cases reaching ≥1 case—the threshold for prompt notification—from day 10 to day 23. Public Health Recommendations: Under lower-transmission conditions, routine vaccination of all Thai pilgrims may not be necessary. However, if MERS-CoV transmission or outbreak activity increases in Saudi Arabia, targeted vaccination should be considered if a safe and effective vaccine becomes available. Further studies should evaluate cost-effectiveness and the combined effects of vaccination and non-pharmaceutical interventions.