Meta-analysis on Serial Intervals and Reproductive Rates for SARS-CoV-2

Ann Surg. 2021 Mar 1;273(3):416-423. doi: 10.1097/SLA.0000000000004400.


Objective: The aim of this study was to systematically review and meta-analyze all literature reporting the basic reproductive number (R0), effective reproductive number (Re or Rt), and the serial interval (SI) values of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection.

Summary background data: To assess the rate at which an infectious disease can spread in a population, the 2 measures, R0 and Re or Rt, are widely used. One of the parameters which influence the calculations is the SI, the period between symptom onset in an infector and an infectee.

Methods: Web of Science, PubMed, Scopus, and Science Direct searching up to May 10, 2020, was performed. A continuous random-effect model was applied using the DerSimonian-Laird (inverse variance) method. Heterogeneity and publication bias were assessed.

Results: A total of 39 articles met the eligibility criteria. Our results demonstrated the mean SI was 5.45 days, with the 95% confidence interval (CI) of 4.23 to 6.66. Pooled estimates for reproduction rates was 3.14 (95% CI: 2.69-3.59) for R0 and 3.18 (95% CI: 2.89-3.47) for Rt. Subgroup analysis by geographical region and date of publication revealed variations over both time and geography in calculated R0 and Rt values. As time has progressed, predicted R0 and Rt values had decreased globally.

Conclusions: The study findings indicate that one SARS-CoV-2-infected person is likely to infect 3 persons, supporting that COVID-19 is a highly contagious disease. As an essential objective metrics implied in risk assessment for this emerging pandemic, monitoring R0 and Re is necessary to indicate the effectiveness or failures of mitigation efforts.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Basic Reproduction Number
  • COVID-19 / epidemiology*
  • COVID-19 / transmission*
  • Humans
  • SARS-CoV-2 / pathogenicity*