Omicron infections have related incubation intervals however shorter era intervals than Delta infections

In a current examine posted to the medRxiv* preprint server, researchers assessed the variations between the generation-interval distributions and incubation intervals of the extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta and Omicron variants.

Study: Inferring the differences in incubation-period and generation-interval distributions of the Delta and Omicron variants of SARS-CoV-2. Image Credit: G.Tbov/Shutterstock
Examine: Inferring the differences in incubation-period and generation-interval distributions of the Delta and Omicron variants of SARS-CoV-2. Picture Credit score: G.Tbov/Shutterstock

Estimation of the variations between SARS-CoV-2 variants with respect to the serial interval, incubation intervals, and era interval distributions is crucial to understanding the transmission of those variants. Nonetheless, the impact of epidemic dynamics is usually ignored whereas estimating the length of an infection and its transmission.

In regards to the examine

Within the current examine, researchers analyzed the serial interval knowledge in addition to the incubation intervals that describe the transmission patterns equivalent to SARS-CoV-2 Omicron and Delta variants.

The crew analyzed time sequence associated to the reported coronavirus illness 2019 (COVID-19) circumstances and the variety of SARS-CoV-2 variants discovered from 29 November 2021 to 30 January 2022 within the Netherlands. Pairs of infector-infectee had been acknowledged by contact tracing whereas knowledge associated to the symptom onset was collected from the nationwide surveillance database. The serial intervals had been subsequently calculated by taking into consideration the distinction between the dates of symptom onset equivalent to the infectee and the infector. One infectee was randomly chosen for every infector to forestall any dependence between the 2 serial intervals.

Moreover, publicly out there knowledge had been aggregated in keeping with the length of the serial interval and didn’t embody info like symptom onset dates, publicity dates, or age. The info aggregated comprised a complete of two,529 transmission pairs which had been additional divided as per the presence or absence of the SARS-CoV-2 spike gene goal failure (SGTF), the week during which the symptom onset date of the infector was, and whether or not the transmission was incident within- or between- households. The crew mixed info reported between 13 December and 26 December 2021 which had been divided into weeks 50 and 51. Within the examine, the transmission pairs who did and didn’t show SGTF had been termed Omicron and Delta pairs, respectively.

Incubation interval knowledge had been obtained from a complete of 513 people which included 255 Delta and 258 Omicron circumstances who reported onset of signs between 1 December 2021 and a couple of January 2022. The crew took into consideration the expansion charges with a view to precisely consider the generation-interval distributions and incubation interval of the Omicron and Delta variants. The expansion charges for the 2 variants had been estimated by first calculating the overall variety of COVID-19 circumstances brought on by every variant by multiplying the variety of circumstances reported per week by the proportion of Omicron and Delta variants detected.

Incubation intervals had been estimated in two distinct methods: ahead and backward. The crew calculated ahead incubation intervals from a bunch of sufferers who had been contaminated at virtually the identical time. Alternatively, backward incubation intervals from a bunch of sufferers who displayed signs at virtually the identical time. 


The examine outcomes confirmed that the variety of SARS-CoV-2 infections contaminated with the SARS-CoV-2 Delta variant continued to say no all through the supply of the examine whereas the time-varying progress charges lowered from virtually -0.01 per day to -0.09 per day by 16 January 2022. The expansion charge subsequently elevated to -0.04 per day by 31 January 2022. The crew famous that the variations within the progress charge coincided with the start of the lockdown laws on 19 December 2021 and their leisure from 15 January 2022. Moreover, the variations within the progress charges between the Omicron and Delta variants lowered over time.

When the expansion charge variations had been accounted for, the Delta and the Omicron variants had been discovered to have comparable incubation-period distributions with a mean of 4.1 days for the Delta variant and 4.2 days for the Omicron variant. Moreover, the distinction between the common ahead and backward incubation intervals was 7% and -22% bias for the Delta and Omicron variants, respectively.

Within the case of within-household transmission pairs, the Omicron variant displayed a shorter common serial interval of three.1 days versus that of the Delta variant which had an interval of three.7 days. Accounting for the expansion charge variations revealed that the imply ahead era interval was 3.0 days for Omicron and three.8 days for Delta. Alternatively, between-household transmission pairs confirmed that the Omicron variant had a mean serial interval of three.0 days whereas the Delta variant had an interval of three.3 days.


General, the examine findings confirmed that the SARS-CoV-2 Omicron infections had related incubation intervals however shorter era intervals than Delta infections. The researchers imagine that surveilling the modifications within the necessary epidemiological parameters associated to SARS-CoV-2 evolution is crucial in estimating its future dynamics.

*Vital discover

medRxiv publishes preliminary scientific reviews that aren’t peer-reviewed and, subsequently, shouldn’t be thought to be conclusive, information scientific follow/health-related conduct, or handled as established info.

Journal reference:



Leave a Reply