SARS-CoV-2 seroprevalence in the urban population of Qatar: An analysis of antibody testing on a sample of 112,941 individuals

Coyle, Peter V.; Chemaitelly, Hiam; Kacem, Mohamed Ali Ben Hadj; Al Molawi, Naema Hassan Abdulla; El Kahlout, Reham Awni; Gilliani, Imtiaz; Younes, Nourah; Al Anssari, Ghada Ali A.A.; Al Kanaani, Zaina; Al Khal, Abdullatif; Al Kuwari, Einas; Butt, Adeel A.; Jeremijenko, Andrew; Kaleeckal, Anvar Hassan; Latif, Ali Nizar; Shaik, Riyazuddin Mohammad; Abdul Rahim, Hanan F.; Nasrallah, Gheyath K.; Yassine, Hadi M.; Al Kuwari, Mohamed Ghaith; Al Romaihi, Hamad Eid; Al-Thani, Mohamed H.; Bertollini, Roberto; Abu-Raddad, Laith J.

The study objective was to assess level of detectable SARS-CoV-2 antibodies in the urban population of Qatar. Antibody testing was performed on residual blood specimens for 112,941 individuals (∼10% of Qatar’s urban population) attending for routine/other clinical care between May 12-September 9, 2020. Seropositivity was 13.3% (95% CI=13.1-13.6%) and was independently associated with sex, age, nationality, clinical-care encounter type, and testing date. Median optical density (antibody titer) among antibody-positive persons was 27.0 (range=1.0-150.0), with higher values associated with age, nationality, clinical-care encounter type, and testing date. Seropositivity by nationality was positively-correlated with the likelihood of having higher antibody titers (Pearson correlation coefficient=0.85; 95% CI=0.47-0.96). Less than two in every 10 individuals in Qatar’s urban population had detectable antibodies against SARS-CoV-2, suggesting this population is still far from herd immunity and at risk of subsequent infection waves. Higher antibody titer appears to be a biomarker of repeated exposures to the infection.