Tracking Delta breakthroughs -- Part 1 (Three disruptive properties)

Last update: Sunday 8/22/21

This is the first in a series of notes that will briefly summarize what every health conscious U.S. resident should know about the Delta variant. It focuses on three properties of Delta that are disrupting the efforts of the U.S. and other nations to employ highly effective vaccines to manage the pandemic in ways that minimize severe illness and death: (1) Delta is far more transmissible than previous variants of the virus, (2) Delta can infect people who have been vaccinated, and (3) These "breakthrough" cases are highly contagious.
 

The Delta variant is highly transmissible

Transmissibility of an infectious disease is measured by its R0 value (pronounced "R naught"). R0 is the average number of other people that a newly infected person will infect during the period in which he or she is contagious. The original coronavirus was estimated to have an R0 = 1.5; the Alpha variant had an R0 = 3.0; and Delta has been estimated to have R0 = 7. Chickenpox has R0 = 10. So contrary to the CDCs recent lament, Delta is not as contagious as chickenpox, but it is far more contagious than previous coronavirus variants.

• "The Delta Variant Isn't As Contagious As Chickenpox. But It's Still Highly Contagious", NPR, 8/11/21

Delta breakthroughs are not rare
Contrary to the CDC's recent pronouncements, breakthrough cases are not "rare" or just a "small percentage" of new infections. At this point no one knows the percentage of new Delta cases that are breakthroughs, but the majority of vaccinated persons in some large clusters of new infections have been breakthroughs, so breakthroughs cannot be "rare" or just a "small percentage" of new Delta infections. Indeed, it's likely that as time goes by, larger and larger percentages of new Delta infections will be breakthroughs.

• Links to anecdotal reports about breakthrough cases are posted in the "Breakthrough" section of this blog's Delta page ==> HERE
  
  

Delta breakthroughs are highly contagious

Delta breakthroughs have been found to carry the same high loads of the virus in their noses and throats as infected persons who have not been vaccinated. So Delta breakthroughs are probably as highly contagious as infected persons who had not been vaccinated.

Additional points of interest

• No herd immunity
  Herd immunity is based on the assumption that vaccinated members of a population that surround unvaccinated members will not pass infections onto the unvaccinated members. As noted in previous paragraphs, Delta can infect vaccinated members and these breakthrough cases can easily infect unvaccinated members. Therefore Delta obliterates all hope that any nation can achieve herd immunity. 
  
  
• Insufficient testing
  The percentage of Delta breakthrough  infections is not known because the U.S. does not routinely perform periodic testing of persons who have been vaccinated.
  
  The vaccines were not designed to eliminate infections; they were designed to greatly reduce severe illness and death, and they still work, especially the highly effective (95%) vaccines produced by Pfizer and Moderna. That's why 97 percent of recent hospitalizations have been for people who were not vaccinated.
  
  Vaccinated persons who become infected usually experience no symptoms or only mild symptoms. As per the previous paragraph, vaccinated persons only account for 3 percent of infected persons whose illness was severe enough to require hospitalization.
  
  Experiencing no symptoms or only mild symptoms when they are infected, most breakthroughs may not be aware that they have been infected, so they won't feel any need to be tested.  No testing also means no contact tracing to identify other people who may have been infected by the breakthrough cases. Indeed, COVID testing is widely regarded to be an onerous activity, so much so that the Biden administration and some governors and mayors are using the threat of repeated testing to pressure unvaccinated employees to become vaccinated. 
  
  
• News reports of Delta breakthroughs
  Fortunately, periodic testing of large samples of the vaccinated population followed by contract tracing is being done in some workplaces, e.g., hospitals, cruise lines, universities, and the staffs of the U.S. president, governors, congressmen, and senators.
  
  Of course, news reports of breakthrough cases in specific workplaces do not provide the kind of systematic data needed to estimate the percentage of Delta infections that are breakthroughs. But if these anecdotal reports increase over time, their increase would provide support for the notion that breakthroughs are occurring more frequently ... unless they become so frequent that the public and the publishers decide that breakthrough cases are no longer newsworthy events ... :-(
  
  Links to anecdotal reports about breakthrough cases are posted in the "Breakthrough" section of this blog's Delta page ==> HERE
  
• 
  

__________________________

Related notes on this blog:

• "Downgrading the CDC's guidance", Last update: 7/25/21
  
  
• "Is the CDC misguiding us again, this time with regards to Delta breakthrough infections???", Last update: 8/13/21
  
  
• "Tracking Delta breakthroughs -- Part 2 (Mitigation via masks)", Last update:  8/22/21
  
  
• "Tracking Delta breakthroughs -- Part 3 (Mitigation via distancing)", Last update: 8/30/21
  
  
• Tracking Delta breakthroughs -- Part 4 (Mitigation via testing and contact tracing)", Last update:  9/5/21