Epidemiology and related hospitalization of COVID- 19 before and during the period of SARS-CoV-2 B.1.617.2 predominance in Tunisia (April-September 2021)

ABSTRACT

Introduction/ Background: By July 202, the SARS-CoV-2 B.1.617.2 variant became the predominant circulating strain, isolated in more than 80%. This study compared indicators of morbidity, mortality and related hospitalization of COVID -19 in two periods April to June 2021, (predominance of B.1.1.7 variant) and July to September 2021 (predominance of B.1.617.2 variant). Methods: National surveillance COVID-19 data concerning morbidity, mortality and related hospitalisation collected by the National Observatory of New and Emerging Diseases from April to September 2021 was analyzed. The following indicators were calculated incidence rate (Crude mortality rate per 100,000 inhabitants was calculated), mortality rate (Crude mortality rate per 100,000 inhabitants was calculated), total hospitalisation rate and intesive care unit hospitalisation rate (hospitalizations per 100,000 persons). These indicators were compared during the period of of B.1.1.7 variant predominance and the period of B.1.617.2 variant predominance. Results: Based on 488054 confirmed cases of COVID-19 during April 1-September 30, 2021, incidence rate increased significantly during the delta predominance period from 1670,5 per 100000 persons to 2515,8 per 100000 persons (p<10-4). We noted a mortality rate of 18,2 per 100000 persons during period before delta variant predominance and 27,3 per 100000 persons during period of Delta variant predominance (p<10-4) whereas we did not find significantly higher rate of related hospitalizations and proportion of Intensive care unit admissions during this period. Impact The results of this study highlighted the impact of the delta variant in the resurgence of COVID -19 in Tunisia during the second phase of the epidemic and the importance of rigorous prevention and control measures to reduce transmission, particularly ongoing vaccination program, and preparedness plans for hospital capacity. Conclusion: The results of this study that took place during the predominance period of B.1.617.2 variant in Tunisia showed significant increase in the incidence and mortality rate . This was probably related to low COVID-19 vaccination coverage, proved effective in reducing the incidence of infection and severe disease.