Backgrounds: COVID-19 is currently spreading around the world, and the cumulative number of cases worldwide exceeded 5 million on 23 May 2020 (10:00 GMT+2). At present, many countries or cities have implemented lockdown measures. This study evaluated the inhibitory effect of lockdown measures on the pandemic by the use of lockdown or similar lockdown in 22 countries or cities.
Methods: An SEIQR epidemiological model was developed to capture the transmission dynamics of COVID-19. With the data related to COVID-19 from 22 countries or cities, the optimal parameters of the model were estimated, respectively.
Results: The average basic reproduction numbers of 22 countries or cities were between 1.5286-3.8067. And Russia Federation, Spain, Italy, France, Germany, the United Kingdom, Singapore, the United States of New York and the United States of New Jersey were hardest hit by COVID-19.
Conclusion: Although the pandemic has not been fundamentally controlled for a short time after lockdown, lockdown was proved to be an extremely effective control measure, which significantly scaled the number of patients down, thereby reduced the harmfulness of the pandemic.