A comparison of transmissibility of SARS-CoV-2 variants of concern

Abstract

Background The World Health Organization (WHO) has currently detected five Variants of Concern of SARS-CoV-2 having the WHO labels of ‘Alpha’, ‘Beta’, ‘Gamma’, ‘Delta’ and ‘Omicron’. We aimed to assess and compare the transmissibility of the five VOCs in terms of basic reproduction number, time-varying reproduction number and growth rate. Methods Publicly available data on the number of analyzed sequences over two-week windows for each country were extracted from covariants.org and GISAID initiative database. The ten countries which reported the highest number of analyzed sequences for each of the five variants were included in the final dataset and was analyzed using R language. The epidemic curves for each variant were estimated utilizing the two-weekly discretized incidence data using local regression (LOESS) models. The basic reproduction number was estimated with the exponential growth rate method. The time-varying reproduction number was calculated for the estimated epidemic curves by the ratio of the number of new infections generated at time step t to the total infectiousness of infected individuals at time t, using the EpiEstim package. Results The highest R0 for the variants Alpha (1.22), Beta (1.19), Gamma (1.21), Delta (1.38) and Omicron (1.90) were reported from Japan, Belgium, the United States, France and South Africa, respectively. Nine out of ten epidemic curves with the highest estimated growth rates and reproduction numbers were due to the Omicron variant indicating the highest transmissibility. Conclusions The transmissibility was highest in the Omicron variant followed by Delta, Alpha, Gamma and Beta respectively.

Genomic epidemiology of the main SARS‐CoV‐2 variants in Italy between summer 2020 and winter 2021

“…The analyzed genomes of SARS-CoV-2 were included in over 100 clusters with a high frequency of mixed clusters (around 70%), which included strains circulating in different regions of the world, suggesting multiple introductions of these lineages/variants in Italy, probably due to international travels. 10 The fact that the earliest clusters were the largest in size, the most persistent, and most frequently mixed could be related to A recently published paper, 28 showing R e estimates obtained on growth rates of VOC genomes stored in public databases from different countries around the world, showed values in Italy similar to those estimated in this study.…”

“…Frequently it was observed the highest values of R e before the circulation of each VOC in Italy (summer 2020 for 20E, autumn 2020 for Alpha and March 2021 for Delta), probably because the initial R e values go back to the origin out of Italy of the epidemics. Deltavariant showed a R e value peak higher than those of 20E and Alpha variants, in agreement with other studies28,29 according to the highest transmissibility of this variant.The estimated R e values were apparently lower than the published R 0 estimates for the different variants (https://ibz-shiny. ethz.ch/covid-19-re-international/).…”

Evolving spike-proteinN-glycosylation in SARS-CoV-2 variants

“…The original SARS-2 strain is believed to have begun as a moderately transmissive virus, infecting its first human host(s) in China in late 2019 5-7 . Since then, SARS-CoV-2 has infected the human population in surges, mutating frequently and evolving into increasingly more transmissive variants 4,8-13 (Figure 1A) . Wuhan-Hu-1, the original SARS-CoV-2 strain, was the dominant strain throughout 2020, and has since produced 5 variants of concern (VoC), as defined by World Health Organization (WHO): Alpha, Beta, Gamma, Delta, and Omicron 14 .…”

Medical resource usage for COVID-19 evaluated using the National Database of Health Insurance Claims and Specific Health Checkups of Japan

“…The Tokyo Olympics took place before the fifth peak, and may have encouraged movement by young people before vaccination. Although the omicron strain was highly infectious, the rate of severe illness is reportedly lower than that of other strains [ 27 , 28 ]. While some vaccines have low efficacy at preventing infection by the omicron strain, vaccination is known to prevent serious illness after infection [ 29 ].…”