Delta breakthroughs cancel herd immunity

 Last update: Thursday 8/12/21

Hotspots are everywhere. At this point every highly vaccinated state, county, city, town, or neighborhood contains hotspots, i.e., smaller communities in which the percentage of people who are not vaccinated is much higher than the percentage within the highly vaccinated surrounding area. Indeed, if you are not vaccinated and you somehow find yourself in a highly vaccinated area for work, dining, or entertainment, you are a hotspot.

Note: The map at the top of this note was obtained from the NY Times' article "Where People Are Most Vulnerable to the Delta Variant" by Charlie Smart that was published on 7/29/21. As per its headline, the map shows the U.S.counties having low lowest vaccination rates: the darker the color, the lower the percentage of vaccinated residents within each county. As the reader can see, the map supports our opening statement that hotspots are everywhere.

Herd immunity before Delta

It's useful to divide the U.S. pandemic into three phases: 

• Mitigation ... January 2020 through January 2021
• Vaccine -- February 2021 through April 2021
• Delta -- May 2021 to present

During the mitigation phase, herd immunity via vaccines was the ultimate goal of the Trump Task Force and the CDC. When someone acquired "immunity" via vaccines and/or infection by the coronavirus, it was assumed that it was unlikely that they could become infected again. When a high enough percentage of the population of a community acquired "immunity", the small percentage who were vulnerable, i.e., not "immune", would be protected from infection by those who were "immune". 

To be specific, if an infected outsider came into the community during the two or three week period in which they were contagious, they would be unlikely to encounter anyone who was vulnerable during this period. At worst, if the contagious newcomer encountered a "Hotspot" -- i.e., a small cluster of vulnerable people -- the infection might spread throughout the hotspot, but would not spread beyond the hotspot to another hotspot.

During the vaccine phase, our experience was consistent with these expectations. Although the vaccines were only guaranteed to prevent severe illness and death,  very few "breakthrough" cases were reported, i.e., very few "immune" persons became infected. But as more transmissible variants appeared, experts began to warn that herd immunity might not be achievable after all.

• "Reaching ‘Herd Immunity’ Is Unlikely in the U.S., Experts Now Believe", Apoorva Mandavilli, NY Times, 5/3/21 ... And a podcast of Mandavilli discussing her article and why she wrote it, The Daily, 5/7/21blah

The experts cited two reasons for their new pessimism: substantial vaccine hesitancy among various segments of the U.S. population and the fact that billions of people outside of the U.S. would not be vaccinated this year or the next facilitated the emergence of substantial variants that might be far more transmissible

Delta ... Moving from pandemic to endemic

Delta has achieved a stunning "breakthrough" for the coronavirus. By developing the ability to infect vaccinated humans as easily as unvaccinated humans in a way that enables them to spread the virus quickly, Delta has converted the entire U.S. population into a vast breeding ground on which more deadly variants can evolve. 

• "Outbreak of SARS-CoV-2 Infections, Including COVID-19 Vaccine Breakthrough Infections, Associated with Large Public Gatherings — Barnstable County, Massachusetts, July 2021", C.D.C., 7/30/21 
  
  
• "C.D.C. Internal Report Calls Delta Variant as Contagious as Chickenpox", Apoorva Mandavilli, NY Times, 7/30/21 
  
  
• "‘It’s Nowhere Near Over’: A Beach Town’s Gust of Freedom, Then a U-turn", Ellen Barry and Beth Treffeisen, NY Times, 8/1/2
  
  
• "How Provincetown, Mass., stress-tested the coronavirus vaccine with summer partying and delta", Hannah Knowles and Randy Dotinga, Washington Post, 8/5/21

There will be no herd immunity at any level -- nation, state. county, city, or neighborhood -- no boundaries over which the Delta cannot cross. Breakthroughs in the surrounding communities will carry Delta from hotspot to hotspot. In the foreseeable future Delta will slosh around the entire U.S., causing no symptoms or mild symptoms on those who are "immune", but inflicting severe illness and death on those who are vulnerable. If the severe illnesses and deaths settle down to levels low enough to become politically "acceptable", we may begin to refer to the contagion as an "endemic" ... until an even more lethal, highly transmissible variant emerges from within the U.S. or from outside.

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Related notes on this blog:

• "Is the CDC misguiding us again, this time with regards to Delta breakthrough infections???" -- Last update: 8/7/21
  
  

• "Is the Delta variant making masks less effective, but more significant?", Last update: 7/15/21