Thread by @KrutikaKuppalli

Latest @WHO #TechnicalBrief on #Omicron
Overall risk remains very high & threat depends on

1⃣Transmissibility of #variant
2⃣How protective vaccines & prior infection are
3⃣Virulence of variant
4⃣Understanding of dynamics & uptake PHSM

Full 🧵👇 (1/)
who.int/publications/m…

Epidemiology (1)
-#Omicron has large growth advantage over #Delta - grows significantly more than Delta in countries with community transmission
- Evidence that immune evasion contributes to rapid spread
-Wk 52, global weekly #COVID19 incidence ⬆️ 71% compared to prior wk
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Epidemiology (2)
-Study from HK found #Omicron infects human bronchus tissue faster and better than #Delta
-#UK study found Omicron outcompetes Delta in experiments using cells derived from human nose, but not seen in lung derived cells
-Growth advantage in upper resp tract
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Epidemiology (3)
-Data from Korea - serial interval of #Omicron was 2.22 days (CI 1.48-2.97) compared to #Delta 3.26 days (CI 2.92-3.6)
-In #SouthAfrica a higher proportion (16%) routinely screened asymptomatic were infected with #Omicron vs 2.6% in #Beta and #Delta
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Transmission (1)
-#Omicron shows significant growth advantage, higher secondary attack rate, and higher observed reproduction number compared to #Delta
- #UK ⬆️risk of household transmission using routine testing data (adjusted OR from #Omicron compared to #Delta 2.9)
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Transmission (2)
-Household SAR in #UK 15.8% for #Omicron and 10.3% for #Delta
-Household SAR in #Denmark 31% for #Omicron and 21% for #Delta
- High growth rate due to immune evasion and increased transmissibility
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Disease severity (1)
-#SouthAfrica, #UK, #Canada, #Denmark suggest reduced hospitalization compared to Delta
-Severity ⬆️ with age, medical conditions, and among people not vaccinated
-Several sources suggest risk of hospitalization and requirement for ventilation lower
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Disease severity (2)
-#UK reported hospitalizations with #COVID19 continue to increase with 9,218 new admits in wk 51 (45% ⬆️ ) over prior week)
-#UKHSA showed 47% reduction in risk of presentation to emergency care or hospital w/ #Omicron vs #Delta
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Disease severity (3)
- #USA 7 day avg of 14, 776 admits btwn 27 Dec - 2 Jan (62.9% increase from prior week)
- #Denmark 0.9% of #Omicron cases have been hospitalized vs 1.1% of other variants
- #Canada shows ⬇️risk of hospitalization and death for Omicron vs Delta (HR 0.46)
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Diagnostics
-Diagnostic accuracy of routinely used #PCR and Ag-#RDT assays does not appear to be impacted by #Omicron
-Studies of comparative sensitivity of Ag-#RDT's are ongoing
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Immunity (1)
-Data suggest there is reduction of neutralizing titers against #Omicron in individuals who have received primary #vaccination or had prior #SARSCoV2 infection
-Increased risk of #reinfection has been reported
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Immunity (2)
-Early data suggests effectiveness of studied vaccines is lower against #Omicron and symptomatic disease than #Delta
-Two studies demonstrate #vaccine efficacy against hospitalization is higher than against symptomatic disease, but lower than against #Delta
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Tropsim
-Preliminary evidence suggest shift in tropism of #Omicron towards the upper respiratory tract as compared to #Delta and wild type virus
-There is evidence of less severe pathogenicity in syrian hamster model
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Therapeutics
-Preliminary data from non-peer reviewed publications suggests some of the mAbs may have impaired neutralization against #Omicron
-#mAbs will need to be individually tested against Omicron
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Re-infection risk (1)
-Risk of reinfection in #England with #Omicron was estimated to be 5.4 fold higher in comparison to #Delta.
- The relative risk was 6.36 and 5.02 for #unvaccinated and #vaccinated respectively
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Reinfection risk (2)
-Report by #UKHSA found that 5.9% of confirmed cases from 1 Nov to 14 Dec due to reinfection
-Relative risk of re-infection from #Omicron at 3.3
- Increased trend of reinfection observed in #Denmark, #Israel #SouthAfrica
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Finally, please read the @WHO #TechnicalBriefs on #Omicron - they have so much great information!

I tried to summarize the important scientific research coming out but it is hard give justice in a twitter thread.

who.int/publications/m…
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