COVID-19 Vaccine Prioritisation in Japan and South Korea

Abstract

Background Due to a limited initial supply of COVID-19 vaccines, the prioritisation of individuals for vaccination is of utmost importance for public health. Here, we provide the optimal allocation strategy for COVID-19 vaccines according to age in Japan and South Korea. Methods Combining national case reports, age-specific contact matrices, and observed periods between each stages of infection (Susceptible-Exposed-Infectious-Quarantined), we constructed a compartmental model. We estimated the age-stratified probability of transmission given contact (q_i) using Bayesian inference method and simulated different vaccination scenarios to reduce either case numbers or death toll. We also performed sensitivity analyses on the proportion of asymptomatic cases and vaccine efficacy. Findings The model inferred age-stratified probability of transmission given contact (q_i) showed similar age-dependent increase in Japan and South Korea. Assuming the reported COVID-19 vaccine efficacy, our results indicate that Japan and South Korea need to prioritise individuals aged 20-35 years and individuals aged over 60 years, respectively, to minimise case numbers. To minimise the death toll, both countries need to prioritise individuals aged over 75 years. These trends were not changed by proportions of asymptomatic cases and varying vaccine efficacy on individuals under 20 years. Interpretation We presented the optimal vaccination strategy for Japan and South Korea. Comparing the results of these countries demonstrates that not only the effective contact rates containing q_i but also the age-demographics of current epidemic in Japan (dominance in 20s) and South Korea (dominant cases over 50s) affect vaccine allocation strategy.

Age-Varying Susceptibility to the Delta Variant (B.1.617.2) of SARS-CoV-2

“…A strength of this model is that we know the diagnostic delay distribution (ie, symptom onset to Q), transmission onset distribution relative to symptom onset (ie, I given symptom onset), and latent period distribution (ie, E to I) based on the robust contact tracing study in South Korea (Table ). 13,23 We assumed that individuals who never developed symptoms (ie, Iasym) had the same latent period distribution as individuals who developed symptoms (ie, Ipresym to Isym) and the same infectious period distribution as the total infectious period of individuals who were symptomatic. 14 With this backward inference method, the remaining variable to estimate was the force of infection (ie, S to E).…”

Evolution of Responses to COVID-19 and Epidemiological Characteristics in South Korea

“…Their shares are high again in P5 and P6, but this overrepresentation was due to the sudden decrease in the share of elderlies that received prioritized vaccinations in those periods. Note that multiple strategies [ 46 , 47 , 48 ] can be formulated for an optimal vaccine allocation to meet specific goals such as the minimization of death rate or incidence rate. While Figure S4 and Table S4 show people in their 20s had a higher rate of infection than other age groups at the Shincheonji incident, the heatmaps in Figure 8 do not reflect this tendency due to the missing information on transmission links.…”

Social imaginaries of digital technology in South Korea during the COVID‐19 pandemic

“…However, South Korean news media's investigative series revealed that the public did not necessarily think that the government's total mobilization and citizens' compliance with it were the main reasons for effective virus control in the country. According to weekly magazine SisaIn 's special series, the public's conscientious and voluntary participation in the health authorities' risk management played a significant role in South Korea's COVID‐19 control (Chun, 2020). Some critics also argued that “corona governance” was not simply top‐down and centralized but also involved active and subjective grassroots participation in the government's pandemic policies (Chekar & Kim, 2022; Jang, 2020).…”