COVID 19: Most Recent Update : Variants

 

         

 

COVID 19 SARS-COV-2 Variants

How SARS-COV2 Infects Us? Nature July 2021

Animation (Click Here)

Major Variants

B.1.617.2  Delta  India Dec 2020

Summary Yale School Of Medicine

  • 80% new cases U.S.
  • 2x more infectious
  • Significantly higher viral loads in infected patients
  • Similar symptom pattern of other strains
    • Less cough affects
    • Less taste and smell affects
  • Similar disease progression (preliminary assessment)

Vaccine Effectiveness  Nature July 2021

  • mRNA Vaccines – Moderna, Pfizer completed 2 dose regimen
    • Only modest reduction in neutralizing titers
    • 88% effective against symptomatic disease
    • 96% effective against hospitalization
    • less than 1% hospitalized patient vaccinated
  • Non-mRNA Vaccines – Oxford-AstraZeneca
    • 60% effective against symptomatic disease
    • 93% effective against hospitalization
  • Natural Immunity
    • Prior infection + vaccination elicits robust immune response.

What Makes Delta Different Structurally?

  • Mutations
    • Spike (S) protein receptor binding sites – multiple
      • Increase binding affinity
      • Avoid immune attack
    • Proteins that increase viral genetic material’s entry into cells

 

B1.1.7  UK Sept 2020

  • Spike protein mutation
  • Increased transmission
  • No increase in severity of disease
  • No reduction in vaccine efficacy

B1.351 South Africa Oct. 2020

  • Spike protein mutation
  • Increased transmission
  • No increased severity of disease
  • Reduced vaccine infection prevention
  • No reduction in vaccine severe disease prevention

Brazil P.1 Jan 2021

  • Spike protein mutation
  • Increased transmission
  • No increased severity of disease
  • Reduced vaccine infection prevention
  • No reduction in vaccine severe disease prevention

 

Variants and Immunity: Cellular Immunity vs Humoral (Antibodies) Immunity

 

Cellular Immunity

NIH News Brief: Does the Immune System Recognize Variants April 2021

  • CD8 T cells from COVID 19 convalescent patients   NIH Research Reference
    • UK B1.1.7 – positive recognition
    • B 1.351 – positive recognition
    • P.1 – Positive recognition
  • Conclusion
    • Cellular immunity in the form of T Cell immune response will be initiated to all variants.
    • Infection is possible but severe disease very unlikely in all variants due to the cellular immunity response.

Antibody Immunity Nature June 2021

  • Previous infection: antibody levels are lower but likely still protective from infection and very likely from severe disease.
  • Vaccination – effectiveness at 6 months  Yale School of Medicine
    • Moderna
      • Symptomatic Infection – 93%
      • Severe Disease – 98%
    • Pfizer
      • Symptomatic Infection – 84%
      • Severe Disease – 97%