BACKGROUND: The incubation period is a crucial index of epidemiology in 
understanding the spread of the emerging Coronavirus disease 2019 (COVID-19). In 
this study, we aimed to describe the incubation period of COVID-19 globally and 
in the mainland of China.
METHODS: The searched studies were published from December 1, 2019 to May 26, 
2021 in CNKI, Wanfang, PubMed, and Embase databases. A random-effect model was 
used to pool the mean incubation period. Meta-regression was used to explore the 
sources of heterogeneity. Meanwhile, we collected 11 545 patients in the 
mainland of China outside Hubei from January 19, 2020 to September 21, 2020. The 
incubation period fitted with the Log-normal model by the coarseDataTools 
package.
RESULTS: A total of 3235 articles were searched, 53 of which were included in 
the meta-analysis. The pooled mean incubation period of COVID-19 was 6.0 days 
(95% confidence interval [CI] 5.6-6.5) globally, 6.5 days (95% CI 6.1-6.9) in 
the mainland of China, and 4.6 days (95% CI 4.1-5.1) outside the mainland of 
China (P = 0.006). The incubation period varied with age (P = 0.005). Meanwhile, 
in 11 545 patients, the mean incubation period was 7.1 days (95% CI 7.0-7.2), 
which was similar to the finding in our meta-analysis.
CONCLUSIONS: For COVID-19, the mean incubation period was 6.0 days globally but 
near 7.0 days in the mainland of China, which will help identify the time of 
infection and make disease control decisions. Furthermore, attention should also 
be paid to the region- or age-specific incubation period.