Assessing Vaccination Prioritization Strategies for COVID-19 in South Africa Based on Age-Specific Compartment Model

The vaccines are considered to be important for the prevention and control of coronavirus disease 2019 (COVID-19). However, considering the limited vaccine supply within an extended period of time in many countries where COVID-19 vaccine booster shot are taken and new vaccines are developed to suppress the mutation of virus, designing an effective vaccination strategy is extremely important to reduce the number of deaths and infections. Then, the simulations were implemented to study the relative reduction in morbidity and mortality of vaccine allocation strategies by using the proposed model and actual South Africa's epidemiological data. Our results indicated that in light of South Africa's demographics, vaccinating older age groups (>60 years) largely reduced the cumulative deaths and the 0-20 first strategy was the most effective way to reduce confirmed cases. In addition, 21-30 first and 31-40 first strategies have also had a positive effect. Partial vaccination resulted in lower numbers of infections and deaths under different control measures compared with full vaccination in low-income countries. In addition, we analyzed the sensitivity of daily testing volume and infection rate, which are critical to optimize vaccine allocation. However, comprehensive reduction in infections was mainly affected by the vaccine proportion of the target age group. An increase in the proportion of vaccines given priority to 0-20 groups always had a favorable effect, and the prioritizing vaccine allocation among the 60+ age group with 60% of the total amount of vaccine consistently resulted in the greatest reduction in deaths. Meanwhile, we observed a significant distinction in the effect of COVID-19 vaccine allocation policies under varying priority strategies on relative reductions in the effective reproduction number. Our results could help evaluate to control measures performance and the improvement of vaccine allocation strategy for COVID-19 epidemic.

Automated summary

Vaccines are crucial in preventing and controlling COVID-19, and designing effective vaccination strategies is essential in reducing infections and deaths. Vaccinating older age groups has shown to decrease mortality, while prioritizing the 0-20 age group as the first strategy is the most effective in reducing confirmed cases. Partial vaccination in low-income countries has resulted in fewer infections and deaths compared to full vaccination. Optimizing vaccine allocation requires considering the sensitivity of testing volume and infection rate, as well as the vaccine proportion for the target age group.