Repeated seroprevalence studies were initially deemed necessary by the policy makers to monitor the progress of pandemics and vaccination programmes. GenScript SARSCoV2 surrogate Virus Neutralization Test. We performed a complex sampling design analysis, calculating sample weights considering probabilities of selection, nonresponse rate and poststratification weight. == Results == The overall weighted prevalence of SARSCoV2 infection was 0.49% (95%CI 0.280.85) (N = 150,857). Among the estimated population with past infection, around 84.1% (95%CI 58.8495.12) (N = 126 826) were asymptomatic, and 90.1% (95%CI 67.0697.58) (N = 135 Lisinopril (Zestril) 866) were undiagnosed. == Conclusions == Our study revealed a low prevariant and prevaccination seroprevalence of SARSCoV2 infection in Malaysia up to midOctober 2020, with a considerable proportion of asymptomatic and undiagnosed cases. This led to subsequent adoption of SARSCoV2 antigen rapid test kits to increase case detection rate and to reduce time to results and infection control measures. Keywords:COVID19, Malaysia, SARSCoV2, seroprevalence, WHOUNITY studies == 1. INTRODUCTION == Coronavirus disease 2019 (COVID19) has rapidly spread globally in an unprecedented manner since it was first detected in December 2019 in China.1On 11 March 2020, the World Health Organization (WHO) declared it a pandemic. By then, 118,319 confirmed cases and 4,292 deaths had been attributed to COVID19 globally.2In Rabbit Polyclonal to Mst1/2 Malaysia, the first imported cases were detected in January 2020, 3and the first local transmission occurred in February 2020.1Together with a few imported cases, these constituted the first wave of the COVID19 pandemic in this Southeast Asian nation with more than 30 million population.4,5The second wave of infection started in March 2020, prompting the government to implement strict public health measures such as mandatory face masking and physical distancing, and even a nationwide movement control order (MCO) that restricted international and most local travels, which successfully flattened the curve in early June 2020. Throughout the ensued recovery MCO when all local travels were permitted again, the number of daily reported COVID19 cases remained relatively low.4Up until the third wave began in midOctober 2020, the alltime cumulative cases were only around 15,000.4,6 This count included only cases with laboratory confirmation of infection by reverse transcriptase polymerase chain reaction (RTPCR), which in turn was performed largely on suspicious cases with respiratory infection and relevant travel history or close contact with a confirmed case.1This is understandable at the initial stage of the COVID19 pandemic, when the disease was not yet known to present asymptomatic or with diverse symptoms.7,8Coupled these with the lack of Lisinopril (Zestril) diagnostic resources and barriers to access healthcare, the incidence figure could be underestimated due to undiagnosed cases, whether symptomatic or asymptomatic.7,8,9,10 SARSCoV2 infection leaves a serological trace in the infected person’s body. The presence of binding antibodies towards the receptorbinding domain (RBD) of the virus indicates past infection, whereas their ability to neutralise the virus indicates that the immunity formed is likely protective.11A survey that examines the seroprevalence of SARSCoV2 early in the pandemic before the advent of vaccination, when only a relatively small proportion of the population had begun to encounter the wildtype virus for the first time, can provide a Lisinopril (Zestril) better understanding to its transmission. This proxy of past infection serves as an additional indicator of disease burden that could quantify the extent of COVID19 underreporting, inform policymakers of the effectiveness Lisinopril (Zestril) of existing public health measures and lead to the improvement of these measures for better disease prevention and control.9,10 During the first year of the pandemic, up to midAugust 2020, the reported seroprevalence of SARSCoV2 infection varied widely globally in the range of 0.422.1% due to epidemiological and study methodology variations, including the type of serology tests used, which differed in their accuracy.10Around the same time, the metaanalysed pooled SARSCoV2 seroprevalence among the general population in the Western Pacific Region was 1.7% (95%CI 0.05.0).12In Malaysia, two studies conducted in health facilities located in.