Evaluation of SARS-CoV-2 Seroprevalence and Variant Distribution During the Delta–Omicron Transmission Waves in Greater Accra, Ghana, 2021

A significant proportion of SARS-CoV-2 infections in Africa were identified as asymptomatic. With the surge of the Omicron variant, asymptomatic participants in epidemiological surveys were key to accurately estimating seroprevalence and true infections in the population. This study assessed seroprevalence, active infections, and circulating variants in Accra, Ghana, during the Omicron wave. Secondary objectives included assessing the association between seroprevalence and sociodemographic factors, vaccination, and adherence to recommended SARS-CoV-2 prevention and control measures. We conducted a cross-sectional survey in Greater Accra in December 2021 using a standardized questionnaire. Serum and naso-oropharyngeal swab samples were collected from 1027 individuals aged ≥ 5 years for the estimation of total antibodies and detection of infection. The study found an overall seroprevalence of 86.8% [95% CI: 84.53–88.77]. PCR test positivity of SARS-CoV-2 was 10%, with the Omicron and Delta variants accounting for 44.1% and 8.8% of infections, respectively. Vaccination (cOR = 10.5, 95% CI: 4.97–26.9, p < 0.001) and older age, particularly the 60+ age group (cOR = 6.05, 95% CI: 2.44–20.2, p < 0.001), were associated with an increase in odds of seropositivity among participants. High seropositivity of SARS-CoV-2 in Accra was an indication of high exposure and transmission rates and/or high vaccine-induced seroprevalence.