The seroprevalence of SARS‐CoV‐2 infection in Malaysia: 7 August to 11 October 2020

BACKGROUND: From the beginning of the COVID‐19 pandemic until mid‐October 2020, Malaysia recorded ~15,000 confirmed cases. But there could be undiagnosed cases due mainly to asymptomatic infections. Seroprevalence studies can better quantify underlying infection from SARS‐CoV‐2 by identifying humoral antibodies against the virus. This study was the first to determine the prevalence of SARS‐CoV‐2 infection in Malaysia's general population, as well as the proportion of asymptomatic and undiagnosed infections. METHODS: This cross‐sectional seroprevalence study with a two‐stage stratified random cluster sampling design included 5,131 representative community dwellers in Malaysia aged ≥1 year. Data collection lasted from 7 August to 11 October 2020 involving venous blood sampling and interviews for history of COVID‐19 symptoms and diagnosis. Previous SARS‐CoV‐2 infection was defined as screened positive using the Wantai SARS‐CoV‐2 Total Antibody enzyme‐linked immunosorbent assay and confirmed positive using the GenScript SARS‐CoV‐2 surrogate Virus Neutralization Test. We performed a complex sampling design analysis, calculating sample weights considering probabilities of selection, non‐response rate and post‐stratification weight. RESULTS: The overall weighted prevalence of SARS‐CoV‐2 infection was 0.49% (95%CI 0.28–0.85) (N = 150,857). Among the estimated population with past infection, around 84.1% (95%CI 58.84–95.12) (N = 126 826) were asymptomatic, and 90.1% (95%CI 67.06–97.58) (N = 135 866) were undiagnosed. CONCLUSIONS: Our study revealed a low pre‐variant and pre‐vaccination seroprevalence of SARS‐CoV‐2 infection in Malaysia up to mid‐October 2020, with a considerable proportion of asymptomatic and undiagnosed cases. This led to subsequent adoption of SARS‐CoV‐2 antigen rapid test kits to increase case detection rate and to reduce time to results and infection control measures.