COVID 19: Most Recent Update : Variants

COVID 19 SARS-COV-2 Variants

How SARS-COV2 Infects Us? Nature July 2021

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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%