COVID-19 Notes
By Dr. Satish K Gupta*
Why did Omicron become the dominant strain the world over?
1. Omicron has the capability to tide over the immunity granted by past infections.
2. Omicron has the fastest transmission which gives it the advantage to out-compete the other existing variants in society.
3. Once established in the throat, Omicron elicits production of neutralising antibodies which can neutralize the past variants reducing the future prospects of older variants to taking over
4. This has been the evolution pattern of Coronaviruses over the years.
5. Omicron wave will wane off when sufficient susceptible hosts develop immunity against infection
6. However, a much faster transmissible variant with higher immunity escape can replace the Omicron to cause a fresh wave of Pandemic.
7. In the case of Omicron, the protection rendered by the previous infection against hospitalisation or death appeared to be robust, regardless of variant. Only time will tell if newer mutants will also follow the same principle. Hopefully so.
A study from Qatar published in NEJM supports many of the above principles
The Study
Natural infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) elicits strong protection against reinfection with the B.1.1.7 (alpha), B.1.351 (beta), and B.1.617.2 (delta) variants. However, the B.1.1.529 (omicron) variant harbours multiple mutations that can mediate immune evasion.
The effectiveness of the previous infection in preventing reinfection was estimated to be 90.2% against the alpha variant, 85.7% against the beta variant, 92.0% against the delta variant, and 56.0% against the omicron variant.
None of the reinfections progressed to critical or fatal Covid-19. The effectiveness with respect to severe, critical, or fatal Covid-19 was estimated to be 69.4% against the alpha variant, 88.0% against the beta variant, 100% against the delta variant, and 87.8% against the omicron variant.
Such protection against reinfection with the omicron variant was lower (approximately 60%) but still considerable. In addition, the protection of the previous infection against hospitalization or death caused by reinfection appeared to be robust, regardless of variant.
Also read: Corona cases declining; How long will the respite last?
*Dr. Satish K Gupta is an MD in Medicines, a Visiting Senior Consultant Physician and Internist at Max Super Speciality Hospital, and a Clinical Assistant Professor at GS Medical College, Chaudhary Charan Singh University, Meerut. He is the author of Journey of COVID in India: A Doctor’s Perspective.
