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AstraZeneca and South African variant (B1.351 or 501Y.V2) vaccine study (it took me a couple of days but here it is… We will probably have another COVID drama in a couple of days). A THREAD:
There were a lot of concerns about this study especially after it reported that the Oxford/AZ vaccine is not effective against the South African variant (effectiveness dropping to 10%) which resulted in South Africa stopping vaccinations with this type of vaccine (1/n)
(btw it lasted one day, they already resumed it). I was hoping that since then we will see the preprint but so far we still only have a YouTube conference and slides from it (unless I missed something). (2/n)
There are several limitations and things which were not mentioned about this study, with the media and the public jumping to conclusions about it straight away fuelling unnecessary panic and anxiety. (3/n)
First of all, yes all vaccines used by us at the moment seem to be less effective against the B.1.351 variant. But less effective does not mean not effective and in most of the cases the level of neutralising antibodies is still high enough to protect us against the infection 4/n
Second, antibodies are not everything, and while they are the easiest to detect they are not even our main defence mechanism against pathogens. While studies detected lower levels of neutralising antibodies after vaccination the T cell immunity was reported to likely remain (5/n)
T cells cannot protect us from becoming infected but they are highly efficient in recognising the pathogen after it manages to get into our body. Then T cells stimulate B cells which in response produce antibodies. (6/n)
Antibodies neutralize the virus. It is a very simplified picture but the main take away point here is that it is all connected and we should not look at it separately if the data exists.(7/n)
According to the SA study, 76 out of 87 epitopes recognized by T cells are unaffected by the B.1.351 mutations. But media did not mention that.(8/n)
Here is a table which summarize the studies about COVID-19 and T cell responses:
https://www.nature.com/articles/s41577-020-0402-6/tables/1
And here is an article about it:
https://www.nature.com/articles/s41577-020-0402-6
(9/n)
https://www.nature.com/articles/s41577-020-0402-6/tables/1
And here is an article about it:
https://www.nature.com/articles/s41577-020-0402-6
(9/n)
What is more, this study was done only on a small and limited group of patients. We need more data to draw conclusions like that. But not only was it a small number of patients but also the vaccination dosage seems to be suboptimal. (10/n)
We know now that the optimal dosage for this type of vaccine is around 12 weeks. The gap between the first and the second doses in the study seemed to be much smaller. (11/n)
In a recent study on AZ vaccine a 12 week gap showed the highest efficacy and the highest level of antibodies generated by the vaccination. So there is a chance that if that gap would be extended in the SA study the reported data would look a lot different.(12/n)
Either way there is really no need to panic about the SA variant, if you got AZ vaccine you are most probably still protected. (13/n)
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https://www.buymeacoffee.com/ECSVirologist
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Just posted as a pre-print https://www.medrxiv.org/content/10.1101/2021.02.10.21251247v1.full.pdf
