Abstract
The infectiousness of COVID-19 is high among the susceptible population, making the calculation of the reproduction number (R) an essential step to implement preventive measures. We aim to estimate COVID-19 transmission to determine if the disease is successfully controlled or extra measured should be adopted to attain this goal. The daily incidence data of COVID-19 in Saudi Arabia from March 2
nd
, 2020, to April 4
th
, 2021, were obtained from the continuously updated Saudi Ministry of Health COVID-19 repository. To get accurate estimation of the situation over the last 4 months (from December 1
st
, 2020, to April 4
th
, 2021), we calculated the weekly (every 7 days) R starting from March 2
nd
, 2020, and till the last week of the available data. The calculated values of R were represented as median, first quantile (Q1), and third quantile (Q3). As early as the first week of December 2020, the median R was 0.81 (0.80–0.83) which means that each existing infected case would transmit infection to only one person. This was followed by fluctuations over the next few weeks around R value of 1, reaching its highest level of 1.45 (1.42–1.47) between December 31
st
, 2020, and January 6
th
, 2021. This was followed by a relatively steady decline over the following weeks, with some till mid-March where the R values started to slightly rise again. Social distancing, protective precautions, avoiding abuse of the partial lifting, expanding the screening process, and other Saudi measures sound to be successful and should be replicated in similar communities. This measure should be continued till the vaccination process is completed, to reduce the number of contacts and to avoid uncontrolled transmission of the disease.