Covaxin tested against two variants B.1.617.2 (India) & B.1.351 (S Africa). Mild reduction in neutralization ability noted; 2.7 and 3-fold, which is a smaller loss compared to other vaccines, reports ICMR/NIV study.
See graph for comparison.
Thread.
1/n biorxiv.org/content/10.110…
See graph for comparison.
Thread.
1/n biorxiv.org/content/10.110…
Neutralizing ability is one of the parameters scientists use to measure a vaccine's firepower against a virus.
If the vaccine is very effective, then its ability will be 1 or close to 1 -that is, in comparison with how effective the same vaccine was against the old virus.
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If the vaccine is very effective, then its ability will be 1 or close to 1 -that is, in comparison with how effective the same vaccine was against the old virus.
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If the virus has become so smart, it will then take several times the original "neutralising power" to kill it.
e.g. If the amount of vaccine required to kill the new variant is 10 times what it took to kill the old virus, we say the neutralising ability is 10-fold lower.
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e.g. If the amount of vaccine required to kill the new variant is 10 times what it took to kill the old virus, we say the neutralising ability is 10-fold lower.
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Thus, if the vaccine is relatively more effective against the variant, then the neutralising ability is perhaps only 1-fold or 2-fold lower.
Knowing this is important when we try to interpret lab studies on vaccines and variants, hence the plain English explanation.
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Knowing this is important when we try to interpret lab studies on vaccines and variants, hence the plain English explanation.
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In this study, ICMR/NIV scientists have found that the GMT (Geometric mean titer) of the vaccine sera were 187.5, 61 and 68.9 against B1 (original), B.1.351 (S. Africa) and B.1.617.2 (Delta, India) respectively.
5/n
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Antibody titers were defined as the highest serum dilution that resulted in >50% (PRNT50) reduction in the number of plaques grown.
The more number of times dilution occurs, the less the antibody in the serum. A powerful vaccine can therefore be diluted MORE no. of times.
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The more number of times dilution occurs, the less the antibody in the serum. A powerful vaccine can therefore be diluted MORE no. of times.
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The neutralizing antibody titer is the reciprocal of the highest dilution that still achieved the result discussed above.
Thus, if the serum was able to be diluted 1/64 times, the titer is 64. If it was diluted further 1/512 times, the titre is written as 512.
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Thus, if the serum was able to be diluted 1/64 times, the titer is 64. If it was diluted further 1/512 times, the titre is written as 512.
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Since these dilutions are multiples, logarithm is used for comparison, because numerically the difference between 256 & 512 seems more than between 4 & 8, even though they represent successive dilutions.
As arithmetic mean is misleading, geometric mean GMT is used here.
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As arithmetic mean is misleading, geometric mean GMT is used here.
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Back to the study; see the whole thread for references about various vaccines and their neutralising ability against B.1.351 variant (chosen here because it has two critical mutations E484K and N501Y among others). Please remember they are not from the same lab.
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Pfizer and AstraZeneca vaccine against B.1.351
(see whole thread for context)
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sciencedirect.com/science/articl…
(see whole thread for context)
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sciencedirect.com/science/articl…
Moderna Vaccine against B.1.351
(see whole thread for context)
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pubmed.ncbi.nlm.nih.gov/33730471/
(see whole thread for context)
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pubmed.ncbi.nlm.nih.gov/33730471/
While reading studies on the topic, it is important to keep some of the following points in mind:
1. Studies done in different labs may not be comparable head-to-head
2. Neutralisation or antibodies only measures a fragment of the immune response generated by vaccine.
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1. Studies done in different labs may not be comparable head-to-head
2. Neutralisation or antibodies only measures a fragment of the immune response generated by vaccine.
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3. There are multiple segments to our immune response that cannot be measured.
4. Heterogeneity is the rule for this virus, there is considerable person-to-person variation in our immune response to this virus and to vaccination; not all of that can be measured in labs.
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4. Heterogeneity is the rule for this virus, there is considerable person-to-person variation in our immune response to this virus and to vaccination; not all of that can be measured in labs.
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*serum generated by a powerful vaccine can be diluted (read as)
[Tweet shortened due to word limit]
[Tweet shortened due to word limit]
Sinopharm, study by Huang et al is linked, not Moderna
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