How SARS-CO2 Infects Us? Nature July 2021
COVID 19 SarsCOV-2 Variants
B.1.1.529 Omicron South Africa Nov 2021
Summary Yale School of Public Health
Compared to Delta Variant
- -Variant Structure (Nature Feb 2022)
- 30 spike protein mutations (Delta has 10)
- Remodeled areas recognized by neutralizing antibodies
- Binds to ACE2 receptors more strongly
- Slower entry of RNA into cells less infectivity in lungs
- Twice as transmissible
- Less severe, less virulent
- 50% less risk of hospitalization
- 10% risk of death
- Vaccine effectiveness
- 2 dose vaccine not as effective
- 3 dose vaccine very effective (80%)
- Chinese vaccine (Sinovac) is not effective
B.1.617.2 Delta India 80% 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
- No difference in disease progression (preliminary assessment)
Vaccine effectiveness Nature July 2021
- mRNA Vaccines – Moderna, Pfizer completed 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 only elicits minimal immune response
- 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
- Spike (S) protein receptor binding sites – multiple
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%
- Moderna