SARS-CoV-2 seroprevalence and extent of infection under-ascertainment in seven regions of Uzbekistan: a population-based serosurvey, May–July 2022

Abstract

Accurate estimation of SARS-CoV-2 transmission was limited in many settings by incomplete diagnostic testing and case reporting. We conducted a population-based cross-sectional serosurvey in seven regions of Uzbekistan between May and July 2022 to estimate SARS-CoV-2 seroprevalence, describe self-reported vaccination coverage, and assess the implications for routine surveillance. A two-stage cluster sampling design was used to randomly select polyclinic catchment areas and registered residents aged ≥5 years. Survey weights accounted for selection probabilities, non-response, and regional population structure. Among 15,000 invited individuals, 13,173 completed both questionnaire and serological testing, corresponding to an 87.8% response rate. Weighted seroprevalence was 98.3% (95% CI 98.0–98.6), indicating extensive cumulative exposure through infection, vaccination, or both. Self-reported vaccination coverage was 59.0% among adults and substantially lower among children. Approximately 243,000 COVID-19 cases had been officially reported nationally by August 2022; however, this national count is not directly comparable with seroprevalence in the seven surveyed regions. Nevertheless, the high seroprevalence, including among groups with low vaccination coverage, is suggestive of substantial transmission not identified by routine case reporting. Population-based serosurveys can therefore complement routine surveillance when interpreted alongside vaccination and epidemiological data.