Mrs Robinah NALWANGA has defended her master thesis on 16/12/2022
Topic: Assessing the impact of vaccination on the dynamics of COVID-19 in Africa: A mathematical modeling study
Multiple effective vaccines are currently being deployed to combat the COVID-19 pandemic in different parts of the world. The deployment of vaccination programs in most African countries is relatively low. Given the contagious nature of COVID-19, there is mounting evidence that poor vaccine uptake may not only result in the amplification of disease transmission in unvaccinated populations but also heighten the risk for vaccinated individuals, especially in such situations where vaccines confer imperfect immunity. In this study, we developed a mathematical model to assess the impact of vaccination programs on curtailing the burden of COVID-19 in ten African countries namely; DR. Congo, Gabon, Rwanda, Kenya, Algeria, Libya, Namibia, South Africa, Benin, and Nigeria. The model stratified the total population into two subgroups based on individual vaccination status. The resulting multi-group model was calibrated using COVID-19 cumulative case data for each of the ten selected countries for the third wave of the COVID-19 pandemic. The detection rate ratio and death rate ratio were used to quantify the vaccine's effectiveness in reducing COVID-19 new infections and deaths, respectively. Additionally, numerical sensitivity analysis was performed to assess the combined impact of vaccination and control measures on the control reproduction number, Rc. Our findings indicate that vaccination significantly reduced secondary transmission among vaccinated individuals. Results also showed that the COVID-19 vaccine prevents COVID-19 disease by reducing the probability of developing symptoms but does not reduce the detection of new infections among symptomatic vaccinated and unvaccinated individuals. The ratio of the number of vaccinated pre-symptomatic and asymptomatic in relation to the unvaccinated increases as the vaccination period increases resulting in a large proportion of undetected cases in most African countries. Similarly, vaccination has a significant impact in preventing deaths that arise from symptomatic cases as compared to confirmed cases. High variation in the vaccine effectiveness against COVID-19 deaths was observed across countries. Furthermore, results from sensitivity analysis revealed that on average, at least 60% of the population in each African country should be vaccinated in order to eliminate the pandemic (lower the Rc below one). Moreover, combining vaccination programs with various levels of NPI adherence will aid in the eradication of the pandemic. For instance, in Algeria, the minimum vaccine coverage required for Rc <1 70%, combined with low (10%) NPI adherence for both unvaccinated and vaccinated individuals. In addition, the elimination is greatly enhanced if the vaccination program is complimented with low (10%) or moderate (30%) adherence to control measures by the unvaccinated and unvaccinated individuals. Vaccination has a significant impact in reducing the transmission, severity of the disease, and COVID-19 deaths, despite low efficacy against COVID-19 infections. There is a need for the African Governments to design vaccination strategies that increase vaccine uptake such as an incentive-based approach.
Keywords: COVID-19, Vaccination impact, Compartmental model, Reproduction number, Africa.