Sero-prevalence of anti-SARS-CoV-2 Antibodies in Addis Ababa, Ethiopia

Background: Anti-SARS-CoV-2 antibody tests are increasingly used for sero-epidemiological purposes to provide a better understanding of the extent of the infection in the community, and to monitor the progression of the COVID-19 epidemic. A sero-prevalence study was conducted to estimate prior infections with SARS-CoV-2 in Addis Ababa. Methods: A cross-sectional study was conducted from April 23 to 28, 2020 among 301 randomly selected residents of Addis Ababa; sub-city health offices, health facilities and health extension workers were contacted, to obtain a population profile and to conduct the random selection of study participants. Participants were selected, who had not been in direct contact with people who had contracted COVID-19, to maintain consistency among the study population. Interviews on socio demographic and behavioural risk factors, followed by serological tests were performed for SARS-CoV-2 IgM, and IgG antibodies, using the COVID-19 IgG/IgM Rapid Test Cassette. Based on the manufacturer information, the test has a sensitivity of 87.9% and specificity of 100% for IgM; and a sensitivity of 97.2% and specificity of 100% for IgG. A Polymerase chain reaction (RT-PCR) test was also done on combined nasopharyngeal and oropharengeal swabs. Findings: The unadjusted antibody-based crude SARS-CoV-2 prevalence was 7.6% and the adjusted (weighted average) SARS-CoV-2 prevalence was estimated at 8.8% (95% CI 5.5%-11.6%) for the study population. Higher sero-prevalence were observed for males (9.0%), age below 50 years (8.2%), students and unemployed (15.6%), as well as those with primary education (12.1%), educated above high school (37.9%), non- smokers (78.7%), with no history of regular alcohol (53.8%), no chat (70.8%), and no shisha use (94.7%). According to the findings, a significantly higher number of individuals had been infected in Addis Ababa as compared to what was being detected and reported by the RT-PCR test, which is suggestive of community transmission.