With input from Dr Monica Vasudev

1483: Herd immunity – ‘combined value of infections + vaccinations as % population > 60%’ – Does this hold up?

Herd immunity refers to the point at which enough individuals have sufficient resistance, or an immune response, to an infectious agent that it has difficulty spreading to others.

Immunity is gained either through vaccination or infection. For contagious diseases that have been noted in modern history, vaccines have helped achieve herd immunity.

Individuals who were infected and recovered from the virus seem to retain some protection for at least 90 days after a positive test. Immunity may be lower and decrease at a faster pace among those who developed little to no symptoms. (Medscape)

1484: The AstraZeneca COVID-19 vaccine has an efficacy of only 10.4% against the South African variant of the virus, suggest data published online in The New England Journal of Medicine. (Medscape)

1485:  The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) have determined new criteria for the classification of variants of SARS-CoV-2. 

The new designations include "variant of interest"; "variant of concern"; and "variant of high consequence." 

• A variant of interest is the one that has led to discrete clusters of infections in the United States or in other countries, or appears to be guiding a rise in cases. It carries gene changes indicating that it might be more transmissible or that may help it to evade immunity conferred by natural infection or vaccination. Treatments and tests may not work as well against it. The CDC is looking at three of these.
• A variant of concern, as proven through scientific research, is more contagious or leads to more severe disease. It may also diminish the effectiveness of treatments and vaccines. People who had previously been infected with COVID-19, may become reinfected by the new strain. The CDC is looking at five of these.
• A variant of high consequence is the one that leads to more severe disease and increased hospitalizations. It leads to failure of medical countermeasures, such as vaccines, antiviral drugs, and monoclonal antibodies. None of the variants thus far fulfil this criteria. (Medscape)

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA