OBJECTIVES: The aim of this study was to conduct a rapid systematic review and 
meta-analysis of estimates of the incubation period of COVID-19.
DESIGN: Rapid systematic review and meta-analysis of observational research.
SETTING: International studies on incubation period of COVID-19.
PARTICIPANTS: Searches were carried out in PubMed, Google Scholar, Embase, 
Cochrane Library as well as the preprint servers MedRxiv and BioRxiv. Studies 
were selected for meta-analysis if they reported either the parameters and CIs 
of the distributions fit to the data, or sufficient information to facilitate 
calculation of those values. After initial eligibility screening, 24 studies 
were selected for initial review, nine of these were shortlisted for 
meta-analysis. Final estimates are from meta-analysis of eight studies.
PRIMARY OUTCOME MEASURES: Parameters of a lognormal distribution of incubation 
periods.
RESULTS: The incubation period distribution may be modelled with a lognormal 
distribution with pooled mu and sigma parameters (95% CIs) of 1.63 (95% CI 1.51 
to 1.75) and 0.50 (95% CI 0.46 to 0.55), respectively. The corresponding mean 
(95% CIs) was 5.8 (95% CI 5.0 to 6.7) days. It should be noted that uncertainty 
increases towards the tail of the distribution: the pooled parameter estimates 
(95% CIs) resulted in a median incubation period of 5.1 (95% CI 4.5 to 5.8) 
days, whereas the 95th percentile was 11.7 (95% CI 9.7 to 14.2) days.
CONCLUSIONS: The choice of which parameter values are adopted will depend on how 
the information is used, the associated risks and the perceived consequences of 
decisions to be taken. These recommendations will need to be revisited once 
further relevant information becomes available. Accordingly, we present an R 
Shiny app that facilitates updating these estimates as new data become 
available.