LATEBREAKER
COVID-19 Pandemic
Assessing COVID-19 disease transmission timelines: a meta-analysis of global average and pooled distributions of SARS-CoV-2 incubation periods Liz Best* Liz Best Tony Cappello Alex Riordan Hannah Mazzotta Stephanie Tack Megan Henry Katrina Stadler Angie Shen
Background: Understanding the average and pooled distribution of COVID-19 incubation periods provides invaluable information when conducting public health and epidemiological assessments of potential or assumed SARS-CoV-2 exposures among individuals and populations. Methods: We conducted an updated systematic literature review, meta-analysis, and pooled distribution analysis of COVID-19 mean incubation period. We qualitatively reviewed 54 relevant publications and included 20 publications in our meta-analysis; 9 studies were used for pooled distribution estimation. Random effects models were used for calculation of the pooled estimates, including mean incubation period, by variant, by country, and mu and sigma distribution parameters. Results: The overall pooled mean incubation period was 4.37 days (95% CI: 4.16-4.59). Meta-RRs decreased with each subsequent variant, with the exception of the beta variant [novel: 5.65 days (95%, 5.02-6.28), alpha: 4.73 days (4.17-5.28), beta: 5.18 (95% CI: 4.93-5.43), delta: 4.23 days (95% CI: 3.91-4.54), and omicron: 3.54 days (95% CI: 3.24-3.84)]. Mean incubation period varied by country with the shortest mean incubation period in Spain [3.23 days (95% CI: 3.04-3.42 days)] and the longest mean incubation period in China [5.28 days (95% CI: 4.57-5.99 days)]. Pooled distribution analysis yielded a lognormal distribution of mu and sigma of 1.19 and 0.51. The highest probability timeline of exposure occurs between 2 and 4 days prior to symptom onset. Conclusions: Pooled risk estimates and distributions of COVID-19 incubation periods from this study can be used to help determine the most probable or likely timeline of exposures based on the date of symptom onset of individual suspected or assumed COVID-19 exposures, particularly in the absence or unavailability of individual case contact tracing, close contact testing, and genomic surveillance.