sharon sanders
Editor-in-Chief & President
1
9
52
Christian Althaus
@C_Althaus
·
5h
Assuming the same generation time, the transmission advantage could act at two levels: 1) increase in transmissibility, 2) immune evasion. We recently developed a mathematical framework to relate differences in growth rates to these properties. 5/15
medrxiv.org
A tale of two variants: Spread of SARS-CoV-2 variants Alpha in Geneva, Switzerland, and Beta in...
Several SARS-CoV-2 variants of concern (VOC) are spreading rapidly in different regions of the world. The underlying mechanisms behind their transmission advantage remain unclear. We measured viral...
2
10
56
Christian Althaus
@C_Althaus
·
5h
A potential increase in transmissibility can be expressed as ρD/R_w, where X is the estimated growth advantage (0.43 per day), D the generation time (5.2 days), and R_w the effective reproduction of the previous variant (~ 0.8 in RSA during October). 6/15 https://ibz-shiny.ethz.ch/covid-19-re-international/…
3
2
40
Christian Althaus
@C_Althaus
·
5h
This would result in an increased transmissibility of 280% (95% CI: 98-468%). With Delta having an R_0 = 5-6 in the Northern Hemisphere during winter, the R_0 of Omicron would be around 10-30. Not impossible, but such a jump seems rather unlikely. 7/15
2
14
68
Christian Althaus
@C_Althaus
·
5h
If the transmission advantage acted via immune evasion only, the level of immune evasion would be ρD(1-Ω)/(ΩR_w), with Ω being the proportion of the population that has fully protective immunity against infection with earlier variants. 8/15

Christian Althaus
@C_Althaus
·
5h
South Africa records an excess mortality of 230k during the pandemic, which corresponds to 0.39% of the overall population (https://github.com/dkobak/excess-mortality…). We earlier estimated the infection fatality ratio for the population of South Africa to be 0.35% (https://doi.org/10.1007/s10654-020-00649-w…). 9/15

github.com
GitHub - dkobak/excess-mortality: Excess mortality during COVID-19 pandemic
Excess mortality during COVID-19 pandemic. Contribute to dkobak/excess-mortality development by creating an account on GitHub.
3
42
Christian Althaus
@C_Althaus
·
5h
Hence, it is likely that almost everyone in South Africa has been infected with #SARSCoV2 and developed partial immunity against reinfection. In addition, 24% of the population have been fully vaccinated. 10/15

1
10
58
Christian Althaus
@C_Althaus
·
5h
Thus, the proportion of the population that is fully protected (‘immune’) against infection and further transmission must be quite high. If we assume Ω = 75%, we get an immune evasion of 93% (95% CI: 32-100%), i.e., Omicron evades protective immunity in 93% of individuals. 11/15
7
22
68
Christian Althaus
@C_Althaus
·
5h
For Ω = 90%, we obtain an immune evasion of 31% (95% CI: 11-52%) ‘only’. This clearly illustrates the current level of uncertainty about Omicron, and I want to emphasize again the preliminary character of these calculations. 12/15
4
12
60
Christian Althaus
@C_Althaus
·
5h
Still, I do expect partial immune evasion to be the main driver of the observed dynamics, but increased transmissibility cannot be ruled out so far. 13/15
2
11
73
Christian Althaus
@C_Althaus
·
5h
The developments in South Africa and observations from other countries during the coming days and weeks will allow us to shed more light on the properties of Omicron. 14/15
1
4
47
Christian Althaus
@C_Althaus
·
5h
Finally, thanks for the amazing work from
@Tuliodna
,
@houzhou
,
@rjlessells
, and their colleagues in South Africa,
@firefoxx66
from
@ISPMBern
at
@unibern
for http://covariants.org,
@richardneher
and
@trvrb
for
@nextstrain
, and the many others working around the clock. 15/15

covariants.org
CoVariants
SARS-CoV-2 Mutations and Variants of Interest
5
7
99
9
52

Christian Althaus
@C_Althaus
·
5h
Assuming the same generation time, the transmission advantage could act at two levels: 1) increase in transmissibility, 2) immune evasion. We recently developed a mathematical framework to relate differences in growth rates to these properties. 5/15
medrxiv.org
A tale of two variants: Spread of SARS-CoV-2 variants Alpha in Geneva, Switzerland, and Beta in...
Several SARS-CoV-2 variants of concern (VOC) are spreading rapidly in different regions of the world. The underlying mechanisms behind their transmission advantage remain unclear. We measured viral...
2
10
56

Christian Althaus
@C_Althaus
·
5h
A potential increase in transmissibility can be expressed as ρD/R_w, where X is the estimated growth advantage (0.43 per day), D the generation time (5.2 days), and R_w the effective reproduction of the previous variant (~ 0.8 in RSA during October). 6/15 https://ibz-shiny.ethz.ch/covid-19-re-international/…
3
2
40

Christian Althaus
@C_Althaus
·
5h
This would result in an increased transmissibility of 280% (95% CI: 98-468%). With Delta having an R_0 = 5-6 in the Northern Hemisphere during winter, the R_0 of Omicron would be around 10-30. Not impossible, but such a jump seems rather unlikely. 7/15
2
14
68

Christian Althaus
@C_Althaus
·
5h
If the transmission advantage acted via immune evasion only, the level of immune evasion would be ρD(1-Ω)/(ΩR_w), with Ω being the proportion of the population that has fully protective immunity against infection with earlier variants. 8/15

Christian Althaus
@C_Althaus
·
5h
South Africa records an excess mortality of 230k during the pandemic, which corresponds to 0.39% of the overall population (https://github.com/dkobak/excess-mortality…). We earlier estimated the infection fatality ratio for the population of South Africa to be 0.35% (https://doi.org/10.1007/s10654-020-00649-w…). 9/15
github.com
GitHub - dkobak/excess-mortality: Excess mortality during COVID-19 pandemic
Excess mortality during COVID-19 pandemic. Contribute to dkobak/excess-mortality development by creating an account on GitHub.
3
42

Christian Althaus
@C_Althaus
·
5h
Hence, it is likely that almost everyone in South Africa has been infected with #SARSCoV2 and developed partial immunity against reinfection. In addition, 24% of the population have been fully vaccinated. 10/15
1
10
58

Christian Althaus
@C_Althaus
·
5h
Thus, the proportion of the population that is fully protected (‘immune’) against infection and further transmission must be quite high. If we assume Ω = 75%, we get an immune evasion of 93% (95% CI: 32-100%), i.e., Omicron evades protective immunity in 93% of individuals. 11/15
7
22
68

Christian Althaus
@C_Althaus
·
5h
For Ω = 90%, we obtain an immune evasion of 31% (95% CI: 11-52%) ‘only’. This clearly illustrates the current level of uncertainty about Omicron, and I want to emphasize again the preliminary character of these calculations. 12/15
4
12
60

Christian Althaus
@C_Althaus
·
5h
Still, I do expect partial immune evasion to be the main driver of the observed dynamics, but increased transmissibility cannot be ruled out so far. 13/15
2
11
73

Christian Althaus
@C_Althaus
·
5h
The developments in South Africa and observations from other countries during the coming days and weeks will allow us to shed more light on the properties of Omicron. 14/15
1
4
47

Christian Althaus
@C_Althaus
·
5h
Finally, thanks for the amazing work from
@Tuliodna
,
@houzhou
,
@rjlessells
, and their colleagues in South Africa,
@firefoxx66
from
@ISPMBern
at
@unibern
for http://covariants.org,
@richardneher
and
@trvrb
for
@nextstrain
, and the many others working around the clock. 15/15
covariants.org
CoVariants
SARS-CoV-2 Mutations and Variants of Interest
5
7
99

