Climate Etc.

By Nic Lewis

 Introduction

Many people, myself included, thought that in the many regions where COVID-19 infections were consistently reducing during the summer, indicating that the applicable herd immunity threshold had apparently been crossed, it was unlikely that a major second wave would occur. This thinking has been proved wrong. In this article I give an explanation of why I think major second waves have happened. Continue reading →

By Nic Lewis

Key points

• A new variant, B.1.1.7, of the SARS-CoV-2 virus has recently spread rapidly in England
• The public health agency’s best estimate of B.1.1.7’s weekly growth rate advantage is 1.51x
• They mis-convert this in a reproduction number ratio of 1.47; converting appropriately gives a ratio of 1.25
• Confident claims by the UK government scientific advisers that the higher growth of B.1.1.7 is due to increased transmissibility are misplaced; it could be partly of wholly due to other factors
• 1.1.7 has not shown a greater growth rate advantage than two previous variants did, both of which are now thought to have no greater transmissibility than previously existing variants
• There is little evidence that B.1.1.7 is more virulent, or likely to be resistant to existing vaccines

Continue reading →

by Judith Curry

I just finished reading an article entitled Asymptomatic Spread Revisited. Continue reading →

By Nic Lewis

An interesting new paper by Marc Lipsitch and co-authors, “Cross-reactive memory T cells and herd immunity to SARS-CoV-2”, has recently been published.[1] It discusses immunological and epidemiological aspects and implications of pre-existing cross-reactive adaptive immune system memory arising from previous exposure to circulating common cold coronaviruses. They argue that key potential impacts of cross- reactive T cell memory are already incorporated into epidemiological models based on data of transmission dynamics, particularly with regard to their implications for herd immunity. I believe that they are mistaken on the herd immunity point, as I will show in this article. Continue reading →

By Nic Lewis

I showed in my May 10th article Why herd immunity to COVID-19 is reached much earlier than thought that inhomogeneity within a population in the susceptibility and in the social-connectivity related infectivity of individuals would reduce, in my view probably very substantially, the herd immunity threshold (HIT), beyond which an epidemic goes into retreat. Continue reading →