The importance of the generation interval in investigating dynamics and control of new SARS-CoV-2 variants

Sang Woo Park, Benjamin M. Bolker, Sebastian Funk, C. Jessica E. Metcalf, Joshua S. Weitz, Bryan T. Grenfell, Jonathan Dushoff

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Inferring the relative strength (i.e. the ratio of reproduction numbers) and relative speed (i.e. the difference between growth rates) of new SARSCoV- 2 variants is critical to predicting and controlling the course of the current pandemic. Analyses of new variants have primarily focused on characterizing changes in the proportion of new variants, implicitly or explicitly assuming that the relative speed remains fixed over the course of an invasion. We use a generation-interval-based framework to challenge this assumption and illustrate how relative strength and speed change over time under two idealized interventions: a constant-strength intervention like idealized vaccination or social distancing, which reduces transmission rates by a constant proportion, and a constant-speed intervention like idealized contact tracing, which isolates infected individuals at a constant rate. In general, constant-strength interventions change the relative speed of a new variant, while constant-speed interventions change its relative strength. Differences in the generation-interval distributions between variants can exaggerate these changes and modify the effectiveness of interventions. Finally, neglecting differences in generation-interval distributions can bias estimates of relative strength.

Original languageEnglish (US)
Article number20220173
JournalJournal of the Royal Society Interface
Issue number191
StatePublished - Jun 15 2022

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Biophysics
  • Biochemistry
  • Biotechnology
  • Biomedical Engineering
  • Biomaterials


  • COVID-19
  • Generation interval
  • Reproduction number
  • SARS-CoV-2
  • Variants of concern


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