There has been a high expectation about the efficacy of coronavirus disease 2019 (COVID-19) vaccines. This research investigates and compares the efficiency of COVID-19 vaccines in five (5) African countries and evaluates the risk or preventive factors inherent in COVID-19 spread. Five different COVID-19 leading African countries in their respective regions (Nigeria, Ethiopia, South Africa, Morocco, and Cameroon) were considered in this study. Population sampling proportional to size concept was used to draw data for two periods (before and during COVID-19 vaccination). A sequential analysis approach was adopted, focusing on the estimates of some epidemiological metrics for the two distinct periods. Nigeria (a wet region) has the lowest risk of COVID-19 incidence during vaccination. The risk of being reported COVID-19 positive in South Africa (a high semi-arid region) is approximately 137 times the number in Nigeria. This study suggests that while vaccination has successfully reduced the case fatality rate in most countries considered except Ethiopia, infection and incidence rates increase during vaccination in all countries except Nigeria. Methods other than vaccination like wearing a face mask, washing hands, and avoiding large gatherings should be intensified to curtail incidence and infection rates.

This study examined the effect of various nitrogen fertilizers in kilograms: 0kg, 30kg, 60kg, and 120kg on varieties of rice: NERICA L-19; NERICA L-20; NERICA L-41; NERICA L-42; and NERICA L-60 from the department of plant physiology and crop production in the college of plant science and crop production Federal University of Agriculture Abeokuta (FUNAAB), Ogun State Nigeria. Also, to determine the appropriate fertilizer at different levels and the best variety for optimum yield of rice and to compare the treatment means for each of the crop varieties. Analysis of Variance technique was used to investigate the effect of various kilograms of nitrogen fertilizers on the yield of the five different types of NERICA rice. The findings revealed that at all the levels of nitrogen fertilizers applied, 30kg of nitrogen fertilizer gave the optimum yield. Further to that, the study discovered that different levels of the nitrogen fertilizers applied did not significantly influence the tons of NERICA rice produced, that is the yield of rice in tons is independent of kilograms of nitrogen fertilizers applied. NERICA L-42 of rice is therefore recommended to farmers to be planted with 30kg of nitrogen fertilizers.