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Shane Crotty Profile picture
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31 Dec 20, 7 tweets, 2 min read
1.  I am convinced that the new "UK variant" of SARS-CoV-2 (B.1.1.7) is a big problem. I look forward to seeing more epidemiology by more labs (not my area), but the overall picture plus these new viral load data now have me convinced. (my PhD was RNA virology)
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2.  An analysis of 641 COVID-19 cases found "S-negative" (B.1.1.7 inferred) cases had 10 to 100-times higher nasal viral loads than 'regular' COVID-19. Virologically, that is a massive difference. It could easily explain higher transmissibility.
doi.org/10.1101/2020.1…
3. The authors of that work are appropriately cautious in their interpretations (e.g. they didn't directly sequence confirm B.1.1.7 cases), and it will be very valuable to see similar studies from other sites. But, I find the data compelling.
4.  For comparison, the D614G mutant causes a 2 to 4 times increase in nasal viral load.
doi.org/10.1016/j.cell…

doi.org/10.1016/j.cell…
5.  Regarding protective immunity:
6. The virology of this mutant may also be complicated. For example, the impact of the ORF8a disruption. Much to learn, and I am anxious to see more data, but the viral load data have me convinced enough that, overall, this mutant is significantly different.
7.  The emergence of this mutant definitely reinforces the importance of vaccinating as many people as fast as possible with COVID vaccines, and to be vigilant about mask wearing and social distancing.

I wish it were different.

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More from @profshanecrotty

Shane Crotty Profile picture
17 Dec 20
A bit more in depth look at the Moderna FDA data.

1. 94% effective at preventing COVID-19

That matches the earlier data and public statements
fda.gov/media/144434/d…
(1/6)
2. Prevents severe COVID-19

Zero cases in the vaccinated group. 30 severe cases of COVID-19 in the placebo group.
(2/6)
3. Worked the same in older adults and other subgroups

That matches the earlier data and public statements.
(3/6)
Read 6 tweets
Shane Crotty Profile picture
29 Nov 20
Got lots of interest in my RNA vaccine explainer yesterday. The most common follow up questions generally fell into two categories, well stated in the tweet below. I will answer both. 1/5

First, to paraphrase: “Isn’t it strange for the immune system to deal with a viral protein from RNA in host cells?” Actually, the human immune system has spent millions of years evolving to recognize viruses this way. (Really, vertebrates have spent 500 million years doing this!)
Viruses regularly express their proteins on infected human cells, and the immune system specifically recognizes those foreign viral molecules. Indeed, many viruses are RNA viruses (they use RNA as their genetic material!), so the immune system is specifically good at this job.
Read 5 tweets
Shane Crotty Profile picture
27 Nov 20
1/ Are RNA vaccines safe? I have gotten this question a lot lately, and it is a good question.
2/ First: RNA is messages. At any moment a human cell has 5000+ different RNA messages, and they are all temporary messages, like post-it notes that get torn up by the cells within minutes or hours after being read.
3/ Or, actually, RNA is like snapchat messages that expire. RNA vaccines do NOT become a permanent part of your body. They are temporary messages instructing cells to make one viral protein temporarily.
Read 9 tweets
Shane Crotty Profile picture
27 Nov 20
1/ This paper is the first significant evidence that recent infection with a common cold coronavirus could have a functional cross protective effect against severe COVID-19. “Recent endemic coronavirus infection is associated with less severe COVID-19"
jci.org/articles/view/…
2/ The possibility of pre-existing (partial) immunity to COVID-19 has been a hot topic. The presence of cross-reactive memory T cells in a fraction of the population opened the possibility of some degree of pre-existing immunity in the population. nature.com/articles/s4157…
3/ Cross-reactive T cells can provide some degree of protective immunity in flu (Sridhar et al., 2013; Wilkinson et al., 2012). The different ways in which such immunity may manifest for SARS-CoV-2 infection are discussed in: nature.com/articles/s4157…
Read 7 tweets
Shane Crotty Profile picture
27 Nov 20
1/ This is one of the most interesting pre-prints I have seen this past month. I consider this study in two parts.
biorxiv.org/content/10.110…
2/ In the first part, Nussenzweig and colleagues show compelling data that memory B cells specific for RBD (the target of neutralizing antibodies against SARS2) undergo affinity maturation over time.
3/ They demonstrate this by cloning mAbs from the memory B cells, sequencing the B cells to show SHM, and characterizing the improved binding capacity of the mAbs.
Read 7 tweets
Shane Crotty Profile picture
27 Nov 20
1/ This is a fantastic new paper in Cell from @PepperMarion showing immune memory to SARS-CoV-2 three months post-infection.
doi.org/10.1016/j.cell…
2/ I particularly like that @PepperMarion made the effort to measure memory CD4 T cells and memory CD8 T cells and antibodies and memory B cells in the same people, instead of just a single component of immune memory.
3/ And yes, I am also happy the results are consistent with our pre-print examining COVID-19 immune memory out to 8 months.😀
Read 4 tweets

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