Undetected breakthroughs spreading Delta everywhere

Last update: Saturday 8/17/21

In March 2020, Dr. Deborah Birx, the response coordinator for President Trump's coronavirus task force, vehemently opposed the suggestion that people who were not healthcare professionals wear cloth masks. Her opposition was based on two judgement calls: first, cloth masks provided no protection against the coronavirus for their wearers; and second, cloth masks might give their wearers a false sense of protection that might cause them to neglect more powerful mitigations, like social distancing. Her pessimistic judgements were soon cast aside; nevertheless in mid-2021 her judgements may prove to be accurate predictions as a result of the most recent flip-flop in CDC guidance. 

In March 2020. there were no scientific studies to support or reject either of her assessments; that's why they have to be regarded as judgement calls rather than as guidance based on science. 

Dr. Birx, the rest of the task force, and the CDC reversed their position on masks in April in a famous flip-flop. While there were still no scientific studies to support their reversal, a substantial body of indirect evidence was accumulated in subsequent months that supported the notion that "universal" wearing of masks in a community substantially reduced the spread of the coronavirus within that community. Readers interested in this scientific evidence and when it was produced should click the links to the following references:

• "Face masks: what the data say", Lynne Peeples, Nature, 10/6/20
•  "An evidence review of face masks against COVID-19", Jeremy Howard et al., PNAS, 1/28/21

A supreme irony

In May 2021 the CDC declared that vaccinated persons could go back to normal living; they would no longer have to wear masks or maintain social distancing in most public places. 

• "Interim Public Health Recommendations for Fully Vaccinated People", Centers for Disease Control, 7/28/21

This declaration of our independence from the virus was challenged by many experts:

• "723 Epidemiologists on When and How the U.S. Can Fully Return to Normal", Claire Cain Miller, Kevin Quealy and Margot Sanger-Katz, NY Times, 5/15/21

Then in late July 2021, the CDC flip flopped after learning about a large number of Delta breakthrough cases, i.e., vaccinated persons who tested positive for the virus, in the crowds that celebrated the July 4th holiday in Provincetown Massachusetts. Over 70 percent of the 900 infected vacationers were fully vaccinated.  Large numbers of breakthroughs in a highly vaccinated community meant that large numbers of breakthroughs could occur anywhere. This was a game changer.

• "‘It’s Nowhere Near Over’: A Beach Town’s Gust of Freedom, Then a U-turn", Ellen Barry and Beth Treffeisen, NY Times, 8/1/21

During this time frame, the CDC also learned about the discovery that vaccinated persons carry about one thousand times as much Delta in their noses and throats as was carried by persons who were infected by the original variant of the coronavirus back in 2020. 

• "Outbreak of SARS-CoV-2 Infections, Including COVID-19 Vaccine Breakthrough Infections, Associated with Large Public Gatherings — Barnstable County, Massachusetts, July 2021", Centers for Disease Control, 7/30/21 

The primary focus of the revised CDC guidance was on wearing masks in communities wherein there was "substantial or high transmission" of the virus, with no mention of distancing. This was a supremely ironic variation of the nightmare feared by Dr. Birx.  Dr. Birx feared that ordinary citizens wearing cloth masks would abandon more powerful mitigations, especially distancing; now comes the CDC recommending that vaccinated persons rely solely on masks.

• "Interim Public Health Recommendations for Fully Vaccinated People", Centers for Disease Control, 7/28/21

Why didn't the CDC just reverse itself and tell everyone everywhere to go back to wearing masks AND social distancing in public places, with no exceptions anywhere for those who were vaccinated?

Provincetown was an area of high transmissibility, but the only reason why we know about its high transmission, i.e., its large number of breakthroughs, was because it was also a highly health conscious community. That's why it performed so many virus tests, then performed the intensive contact tracing and testing required to identify all of the people who were infected and their vaccination status. Less than ten of the 900 infected persons required hospitalization; the rest were either asymptomatic or mild. 

Breakthrough cases are usually mild or asymptomatic, so high transmission among breakthroughs won't be detected in most communities regardless of their vaccination percentages. High transmission will usually be detected when cases are severe. In other words, the CDC's revised guidelines will be applied in communities where vaccination percentages are low, but not in communities where vaccine percentages are high. From these considerations we can infer three disturbing outcomes

1. Breakthroughs in high vaccination communities will lead "normal lives" while spreading Delta, unrestrained by masks or social distancing.
   
   
2. Breakthroughs wearing masks will spread Delta in low vaccination communities, unrestrained by social distancing. Indeed, some of the recent surge in Delta infections, hospitalizations, and deaths among the unvaccinated may have been propelled by undetected breakthroughs. 
   
   
3. Delta's ability to infect the entire U.S. population, i.e., vaccinated and unvaccinated, will provide it with 330 million opportunities to evolve more lethal variants.

__________________________

Related notes on this blog:

• "Delta breakthroughs cancel herd immunity", Last update: 8/12/21
  
  

• "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