Estimating the infection burden of COVID-19 in Malaysia

Abstract

Malaysia has reported 2.75 million cases and 31,485 deaths as of 30 December 2021. Underestimation remains an issue due to the underdiagnosis of mild and asymptomatic cases. We aimed to estimate the burden of COVID-19 cases in Malaysia based on an adjusted case fatality rate (aCFR). Data on reported cases and mortalities were collated from the Ministry of Health official GitHub between 1 March 2020 and 30 December 2021. We estimated the total and age-stratified monthly incidence rates, mortality rates, and aCFR. Estimated new infections were inferred from the age-stratified aCFR. The total estimated infections between 1 March 2020 and 30 December 2021 was 9,955,000-cases (95% CI: 6,626,000-18,985,000). The proportion of COVID-19 infections in ages 0-11, 12-17, 18-50, 51-65, and above 65 years were 19.9% (n = 1,982,000), 2.4% (n = 236,000), 66.1% (n = 6,577,000), 9.1% (n = 901,000), 2.6% (n = 256,000), respectively. Approximately 32.8% of the total population in Malaysia was estimated to have been infected with COVID-19 by the end of December 2021. These estimations highlight a more accurate infection burden in Malaysia. It provides the first national-level prevalence estimates in Malaysia that adjusted for underdiagnosis. Naturally acquired community immunity has increased, but approximately 68.1% of the population remains susceptible. Population estimates of the infection burden are critical to determine the need for booster doses and calibration of public health measures.

Fig 1. Cases in Malaysia between 1 October 2020–30 December 2021 in Malaysia.

a) Daily incidence rate by age categories across time, b) Heatmap of daily incidence rate by age categories across time (Data before 1 September 2020 were removed as deaths were relatively lower to increase visualization quality)

Fig 2. Deaths in Malaysia between 1^st October 2020-30^th December 2021 in Malaysia.

a) Daily deaths by age categories across time, b) Heatmap of daily mortality rate by age categories across time (Data before 1 September 2020 were removed as deaths were relatively lower to increase visualization quality).

Fig 3. Comparison of reported aCFR of COVID-19 in Malaysia by age categories from 1 March 2020–30 December 2021 in Malaysia compared to assumed IFR and literature-derived IFR

Fig 4. Comparison of reported COVID-19 cases to estimated COVID-19 infections.

a) cumulatively and b) by age categories from 1 March 2020–30 December 2021 in Malaysia.