An Age-stratified Population-based COVID-19 Seroprevalence Study Protocol for NHMS 2020

Introduction Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has reached pandemic level since it was first detected in China at the end of December 2019. As of 11 August 2020, close to 20 million cases were reported worldwide, of which 9,094 were detected in Malaysia1 . Due to the presence of asymptomatic and mild clinical manifestation, the actual number of COVID-19 infections is higher and can be quantified through a seroprevalence study. This study aims to estimate the overall and age-stratified COVID-19 seroprevalence among the general population in Malaysia. Materials and Methods This study is a component of National Health and Morbidity Survey (NHMS), which happens to focus on communicable diseases in year 2020. NHMS is a community-based cross-sectional survey conducted by the Institute for Public Health (IKU) in the general population every year with different health topics using two-stage stratified random sampling. The sampling frame is a list of arbitrarily defined geographically contiguous areas called enumeration blocks (EB), each of which contains 80 to 120 living quarters (LQ) with 500 to 600 people. A total of 100 EB, and 20 living quarters (LQ) within each EB, were selected nationwide. All non-institutionalised individuals ≥ 1-yearold in the selected LQ will be recruited. We expect 1622 children (<18 years) and 3378 adults (≥18 years) to participate in this study. Data collection will be conducted from August to October 2020 throughout the country by 12 teams of trained data collectors, a third of which is deployed to East Malaysia. Scouters will first visit selected LQ upon arrival at an EB to recruit eligible individuals. Willing respondents will be given an appointment to go to a pre-determined health facility or a temporary data collection station for face-to-face interview and blood sampling. Socio-demographic characteristics including housing and environment, comorbidities with past and current smoking status, as well as factors associated with COVID-19 and its signs and symptoms will be captured using mobile tablets. A trained nurse or medical assistant will collect 5 ml (3.5 ml for children < 7-year-old) of venous blood from each respondent in gel tube with clot activator. Clotted blood specimens will be centrifuged on-site and and chilled at 2-8 °c until they reach a virology laboratory in the Institute for Medical Research (IMR) within 72 hours. Temperature will be monitored using electronic logger with its dedicated software. All specimems will be tested in IMR by trained laboratory personnel on SARS-CoV-2 immunoglobulin M and G (IgM/IgG) enzyme-linked immunosorbent assay (ELISA), and positive specimens will be further tested with surrogate virus neutralisation test (sVNT). Complex sample analysis will be used to produce descriptive and inferential statistics representative of Malaysian population. The study is given ethical approval by the Medical Research and Ethics Committee, Ministry of Health Malaysia (NMRR-20-1166-55133 (IIR)). Results We expect an overall COVID-19 seroprevalence in Malaysia of up to 3.0% by IgM or IgG ELISA, and <1.0% by sVNT. The prevalence might be slightly higher than the above figures among adults. Discussion / Conclusion To date, many COVID-19 seroprevalence surveys were performed around the world, some of which were communitybased. Among the latter, COVID-19 seroprevalence ranged from 0.6% in Chengdu city, China3 , to 33.0% in Guilan province, Iran4 . Most studies reported a seroprevalence of