Abstract
BACKGROUND: This study examines in-hospital mortality among children and adults hospitalized with COVID-19 across the pre-Delta, Delta, and Omicron waves in the African region. METHOD: We conducted a retrospective cohort study using individual-level data from 520,810 hospitalized children and adults in 13 African countries. Cox proportional hazards regression models were used to assess the impact of SARS-CoV-2 variants on in-hospital mortality. FINDINGS: Among children, the risk of in-hospital mortality was comparable between pre-Delta and Delta waves (aHR 1.02, 95% CI 0.77-1.35). In adults, mortality increased by 6% during Delta wave compared with pre-Delta wave (aHR 1.06, 95% CI 1.04-1.09). During Omicron wave, mortality risk decreased significantly by 42% in children (aHR 0.58, 95% CI 0.43-0.80) and 59% in adults (aHR 0.41, 95% CI 0.40-0.43) compared to the Delta wave. Notably, the reduction in mortality risk during the Omicron wave was less pronounced for children with severe or critical COVID-19, those co-infected with HIV, and adults co-infected with either HIV or tuberculosis. CONCLUSION: Despite a general reduction in mortality risk during Omicron wave, persistently high mortality in specific high-risk groups underscores the importance of prioritizing booster vaccinations and intensified treatment for vulnerable populations as per WHO recommendations.