First national household seroprevalence survey of SARS-CoV 2 antibodies in Tunisia, April 2021

ABSTRACT

Introduction/ Background: Population-based serosurveys measuring anti- SARSCoV- 2 antibodies are indicated for monitoring and estimating the real extent of the epidemic. This study aims to estimate the seroprevalence of SARS-CoV-2 antibodies among the Tunisian population. Methods: A national household cross sectional study was conducted in Tunisia on April 2021 among adults aged ≥18 years regardless gender, geographical distribution, and vaccination status using a random stratified two stage sampling. A sample size of 10000 subjects was calculated using Openepi Software. Trained interviewers collected data using a standardized electronic questionnaire (CSPAmong software) on sociodemographic characteristics, symptom history, and exposure factors. Blood samples were collected to identify IgG Antibodies, using ELISA test. Data analysis was performed using SPSS 26 and R. Estimations were adjusted to sample design and non-response rate. Results: A total of 9833 individuals from 5039 households were enrolled in the study. The weighted national seroprevalence was 29.5% (95%CI [28.2-30.8%]). It varied between governorates, ranging from 19.9% (95%CI [15.3%-25.5%]) in Kasserine to 41.9 % (95%CI [39.2%-49%]) in Kebili. The highest seroprevalence was among female 30.7%(95%CI [29.1%-32.3%]) Vs 28.2%(95%CI [26.3- 30.1%]) among male and age group 55-64 years 33.8% (95%CI [31.2%- 36.5%]). The lowest seroprevalence was among group age 18-24 25.9% (95%CI [22.4%-29.8%]. Impact Our study provides estimates on national SARS-CoV- 2 seroprevalence showing significant variations between affected area. Highest seroprevalence where recorded in regions were circulation of SARSCoV- 2 occurred intensively and earlier during the first wave. Conclusion: This is the first national household seroprevalence survey of SARS-CoV-2 antibodies in Tunisia. Findings from this study are useful for adjusting vaccineprioritization decisions and guiding preventive measures especially for susceptible population with lower seropositivity rates.