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Vipin M. Vashishtha Profile picture
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Jan 19 • 4 tweets • 2 min read
A new study from #Thailand

#COVID19 breakthrough infection after #CoronaVac inactivated vaccine induced robust antibody responses & cross-neutralization of #SARS2 variants, but less immunity against #Omicron

1/
Binding antibody levels in sera from patients with breakthrough infection (BI) were significantly higher than those in individuals who had received AstraZeneca Vaccine as a third vaccination. 2:
However, neutralizing activities against wild-type and variants including Alpha, Beta, & Delta were comparable in patients with BI & individuals who received a 3rd vaccination with AZ vax, which activities are exceeding 90%. 3/
Omicron was neutralized less effectively by serum from BI patients, with a 6.3-fold reduction compared to Delta.

The study suggests that breakthrough infections after 2 doses of CoronaVac vaccine can induce neutralizing antibody against Omicron. 4/

medrxiv.org/content/10.110…

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More from @vipintukur

Vipin M. Vashishtha Profile picture
Jan 21
A lot of people around the world are feeling elated & treating emergence of #Omicron as a signal of the end of the pandemic! Most believe it will bring “endemicity".

Does it make sense? 1/
How can anyone think we’ve got this under control when a new #variant suddenly pops up, nearly completely evades immunity & then sweeps the world in a few weeks?
Further, we must know “mutations have no schedule.” Could be 4-6 months, could be next week. 2/
“to what extent will #Omicron-like emergence events characterize "endemic" circulation of #SARS2? Given it occurred once, having it occur again would not be at all surprising,…whether to expect this every year or every ten.” 3/

Read 5 tweets
Vipin M. Vashishtha Profile picture
Jan 20
How come #COVID19 is mostly mild in children? And why do #MISC affect mostly young people?

An interesting hypothesis by @BrodinPetter considering the trade-off between growth and immunity, while most of the studies focus on resistance rather than tolerance 1/
Tolerance to the initial infection may allow virus to stay in gut longer, leak through gut wall, and trigger T cell activation. Could a milder systemic immune response lead to viral persistence in the gut of children? 2/ ImageImage
“Energy allocation for growth increases the threshold to mount expensive systemic inflammatory responses unless absolutely required”
3/ Image
Read 5 tweets
Vipin M. Vashishtha Profile picture
Jan 19
What do we know about BA.2-sub-lineage of Omicron? Is BA.2 different?

BA.2 shares 32 mutations w/ BA.1, but it also has 28 unique mutations. Some diff in S1. E is the same, N & M are diff in 1 mutation between the two variants.
And...quite a difference when we go to ORF1ab. 1/ Image
1-Transmissibility:
Consistent growth across multiple countries is evidence BA.2 may be some degree more transmissible than BA.1.

2-Virulence:
*Very* early observations from India and Denmark suggest there is no dramatic difference in severity compared to BA.1. 2/
3-Immune evasion:
Minimal differences in VE ag. BA.1 & BA.2 and, its also highly likely BA.1 infection will give decent cross-reactivity ag BA.2 infection.

4-Antigenicity:
The Spike RBD mutations are likely to have a fairly minimal impact on antigenicity compared to BA.1. 3/
Read 5 tweets
Vipin M. Vashishtha Profile picture
Jan 19
📌 A must-read article, the missing link?

What we know so far?

1-The dysregulation of innate and adaptive immunity has been recognized to play a critical role in the clinical outcome of COVID-19 patients. 1/
2-Severe evolution of COVID is thought to be driven by hyperactivated innate immunity in addition to adaptive immune defects resulting in lymphopenia & neutrophils/lymphocytes imbalance

3-A deficient IFN response has also been shown to favor or result from SARS2 infection 2/
These immunological dysregulations are thus underlying hyper-immune reactions such as the “cytokine storm” syndrome, MIS-C, dysregulation of coagulation, as well as neurological & various other manifestations 3/
Read 25 tweets
Vipin M. Vashishtha Profile picture
Jan 19
A new modelling study on the value of vaccine boosters to mitigate the global impact of #Omicron

By fitting an immunological model to population-level vaccine effectiveness (VE) data, NAb titres for Omicron are reduced by 3.9 fold compared to the Delta variant 1/
Under this model, it is predicted that 90 days after boosting with the Pfizer-BioNTech vaccine, efficacy against severe disease (admission to hospital) declines to 95.9% against the Delta & 78.8% against the Omicron 2/
Integrating this immunological model within a model of SARS2 transmission, the size of the Omicron wave will depend on the degree of past exposure to infection across the population, w/ relatively small Omicron waves in countries that previously experienced a large Delta wave 3/
Read 7 tweets
Vipin M. Vashishtha Profile picture
Jan 19
The current narrative is, “Covid vaccines prevent severe disease & deaths.”This is going back on the stated primary endpoint “prevention of symptomatic disease.”
Why is it important to avoid symptomatic disease even during the #Omicron surge? 1/

Even infection is worrisome: may damage/destroy T cells! According to T cells expert @fitterhappierAJ “CD95-mediated [T cell] differentiation & death may be advancing T cells to greater effector acquisition, fewer numbers, & immune dysregulation.” 2/

frontiersin.org/articles/10.33…
T cells are decreased and exhausted in patients with COVID-19. Cytokines such as IL-10, IL-6, and TNF-α might be involved in T cell reduction. 3/

frontiersin.org/articles/10.33…
Read 6 tweets

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