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/
Booster doses can have a major impact in mitigating the epidemic peak, although in many settings it remains possible that healthcare capacity could still be challenged. 4/
This is particularly the case in #ZeroCovid countries where there is little prior infection-induced immunity and therefore epidemic peaks will be higher. 5/
Where dose supply is limited, targeting boosters to the highest risk groups to ensure continued high protection in the face of waning immunity is of greater benefit than giving these doses as primary vaccination to younger age-groups. 6/
In many settings it is likely that health systems will be stretched, and it may therefore be necessary to maintain and/or reintroduce some level of NPIs to mitigate the worst impacts of the Omicron as it replaces the Delta variant. 7/

medrxiv.org/content/10.110…

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More from @vipintukur

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
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
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
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
Jan 19
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/
Read 4 tweets
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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