The link between the viral variant and length of the COVID-19 incubation period is still a matter of debate. Scientists from the Institut Pasteur conducted a survey of thousands of volunteers for more than a year to provide an answer.
Launched in October 2020, the ComCor study investigates the environment, practices and places visited by people recently infected with SARS-CoV-2. The aim is to identify factors that might influence the COVID-19 incubation period, in other words the time between an infectious contact with the virus and the onset of the first symptoms.
In a study published in The Lancet Microbe, Institut Pasteur scientists analyzed data from more than 20,000 individuals who had been infected with a known variant of SARS-CoV-2 following a single contact with an infectious person. This approach enabled them to compare the COVID-19 incubation period for the different SARS-CoV-2 variants.
Individual factors for thousands of volunteers
"We observed an average incubation period of four and a half days with the historical variant compared with three and a half days with the Omicron variant, so a reduction of one day over the entire study duration," reports Arnaud Fontanet, Head of the Institut Pasteur's Epidemiology of Emerging Diseases Unit and principal investigator of the study.
"We also showed that the incubation period was shorter when the infectious person was symptomatic and the person infected was not wearing a mask, which suggests that a higher infectious dose of the virus could shorten the incubation period," explains Simon Galmiche, a scientist in the unit and first author of the study.
ComCor is a collaborative project between the Institut Pasteur, the French National Health Insurance Fund (CNAM), Santé Publique France and Ipsos. It is funded by ANRS | Emerging Infectious Diseases and the Fondation de France via the "United against the virus" alliance. In 2020 it was awarded the CAPNET "national research priority" label.
This study is part of the priority scientific area Emerging infectious diseases of the Institut Pasteur's strategic plan for 2019-2023.
SARS-CoV-2 incubation period across variants of concern, individual factors, and circumstances of infection in France: a case series analysis from the ComCor study, April 18, 2023, The Lancet Microbe
Simon Galmiche, Thomas Cortier, Tiffany Charmet, Laura Schaeffer, Olivia Chény, Cassandre von Platen, Anne Lévy, Sophie Martin, Faïza Omar,
Christophe David, Alexandra Mailles, Fabrice Carrat, Simon Cauchemez, Arnaud Fontanet