Very interesting analyses about the virology of #Omicron, which may explain the faster spread of this variant.
According to a new lab study, Omicron infects & multiplies ~70x faster than the Delta variant and the wild type SARS-CoV-2 in the human bronchus, but not in the lung.
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Another analysis by
@BalazsLab also supports these findings. In this lab study w/ pseudoviruses, Omicron showed greater ability to infect cells than other variants, which was ~ 4 times more infectious than the original strain, also more than Delta. https://www.medrxiv.org/content/10.1101/2021.12.14.21267755v1/ …pic.twitter.com/0fKoAE2LfX
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These preliminary laboratory analyses indicate that;
Omicron is significantly more transmissible than delta
Less efficient replication in the lungs may suggest lower severity, but severity in humans is not determined only by virus replication but also the host immune responseShow this thread -
Important to note that first study is an ex vivo work, meaning that human tissue is used to look at virus replication in the lab. So, this is not a definitive but supportive finding & needs to be confirmed by clinical data as host immune response is absent in these studies.
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Lay summary: These results indicate inherent transmissibility & replication advantage of Omicron (in addition to immune evasion) compared to delta. It also explains why it spreads quickly and outcompeted delta in SA, which fits w/ modelling assumptions.https://twitter.com/mugecevik/status/1466845357686640640?s=20 …
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For those asking whether this is good/bad news, simple answer: I don't know. While omicron may infect the lung cells less efficiently, a higher viral load may worsen immune response. We discussed the pathogenesis w/
@KindrachukJason@KrutikaKuppallihttps://www.bmj.com/content/371/bmj.m3862 …Show this thread -
The only thing I am sure of is that omicron will spread so quickly through the population, making it likely impossible to contain even with the most stringent measures & giving us very little time over the next few weeks. So get your vaccines & boosters!https://twitter.com/mugecevik/status/1468518680157999106?s=20 …
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Can we assume that the study is done in lung tissue with 'no immunity' from natural or vaccine induced immunity? (there is no detail in the write-up I can see) Thanks in advance
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Notable that the 10x number is compared to the original and not delta - and that there is no significant difference compared to delta (which wasn‘t less severe than the original). Still hopeful, but don’t love the different comparisons in the two. Thanks for sharing!
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The graph posted above clearly shows Omicron at 10x both the original and delta variants at 24 hours. Are you referring to a different graph?
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Mechanistically, why would changes in spike affect the speed of replication? More in/more out? More cells hit simultaneously?
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There’s a lot we don’t yet understand about Omicron, including its impact on immunity and what it means for vaccines. New data will be emerging over the next few wks, which could be misinterpreted w/o context. What we might expect & how to interpret the emerging data?
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