Article Text

Download PDFPDF

Original research
Incubation period of COVID-19: a rapid systematic review and meta-analysis of observational research
  1. Conor McAloon1,
  2. Áine Collins2,
  3. Kevin Hunt3,
  4. Ann Barber2,
  5. Andrew W Byrne4,
  6. Francis Butler3,
  7. Miriam Casey2,
  8. John Griffin5,
  9. Elizabeth Lane6,
  10. David McEvoy7,
  11. Patrick Wall7,
  12. Martin Green8,
  13. Luke O'Grady1,8,
  14. Simon J More2
  1. 1Section of Herd Health and Animal Husbandry, School of Veterinary Medicine, University College Dublin, Dublin, Ireland
  2. 2Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Dublin, Ireland
  3. 3Centre for Food Safety, School of Biosystems and Food Engineering, University College Dublin, Dublin, Ireland
  4. 4One Health Scientific Support Unit, Department of Agriculture, Food and the Marine, Dublin, Ireland
  5. 5Straffan, Kildare, Ireland
  6. 6Backweston Campus, Department of Agriculture, Food and the Marine, Celbridge, Ireland
  7. 7School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
  8. 8School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
  1. Correspondence to Dr Conor McAloon; conor.mcaloon{at}


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.

  • epidemiology
  • public health

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:

Statistics from


  • Twitter @AndyByrneSci, @MiriamC51755360

  • Contributors CM conducted the eligibility screening of shortlisted studies, extracted the data and conducted the analysis with input from all authors. ÁC, KH and FB conducted the initial literature searches. CM and SJM completed the initial drafts of the manuscript. MG and LO reviewed the statistical methods. All authors (CM, ÁC, KH, AB, AWB, FB, MC, JG, EL, DM, PW, MG, LO, SJM) read and approved the final manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests All authors have completed the ICMJE uniform disclosure form at and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information. The data for the meta-analyses conducted are included in the manuscript.

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Linked Articles