Is the CDC misguiding us again, this time with regards to Delta breakthrough infections???

Last update: Friday 8/13/21

The CDC's Interim Public Health Recommendations for Fully Vaccinated People (7/28/21) declares that "Infections happen in only a small proportion of people who are fully vaccinated, even with the Delta variant." Let's ask ourselves the crucial question: how would the CDC know that the proportion of Delta breakthrough cases is small? 

Random tests of vaccinated individuals

Had the CDC or some other public health agency conducted follow-up tests of random samples of vaccinated persons from time to time, the results would have provided plausible estimates of the percentage of vaccinated persons who became infected by the Delta variant. In other words, these tests of random samples of vaccinated persons would mimic the testing procedures of the clinical trials of the vaccines with regards to the original virus.

A public health agency could not rely on information obtained from vaccinated persons who volunteered to be tested for Delta because most infections of vaccinated persons would either be asymptomatic or so mild that most breakthrough cases might might not realize that they had been infected.

Contact tracing of breakthrough cases

Random tests would also provide opportunities for public health officials to obtain plausible answers to a related vexing question: How contagious are breakthrough cases? In other words, if a vaccinated person becomes infected by Delta, is he or she less contagious than an unvaccinated person who becomes infected? Public health officials could answer this question by following up each breakthrough case with intensive contact tracing and testing.

Again, it's likely that most of the vaccinated persons who were infected by a breakthrough case would either be asymptomatic or too mild for them to realize that they had been infected until the contact tracer suggested that they be tested.

Possible outcomes

Each of these questions might have benign answers:

• If the percentage of breakthroughs in the vaccinated population was small, e.g., one percent or five percent, and if most of these cases were either asymptomatic or mild, they would only have marginal impact on our health care system.
• If the percentage of breakthroughs was not small, but breakthrough cases were not contagious or were far less contagious than ordinary Delta infections, then again, their impact on our health care system would be marginal.

There is no indication that the CDC or any other public health agency conducted the kinds of studies described in the preceding paragraphs. So we must conclude that the CDC's declaration that the percentage of breakthrough cases is small might be yet another bad judgement call that they are trying to pass off as finding of "the science".

Unfortunately, some data about large breakthrough clusters that's emerged from other sources in recent weeks suggests that we are actually facing the worst possible pair of outcomes: the percentage of breakthroughs is not small AND breakthroughs are as highly contagious as ordinary Delta infections.

Large breakthrough cluster in Provincetown, Massachusetts

Provincetown is a beach resort community on Cape Cod that is popular within the gay community. After the July 4th, 2021 weekend, over 900 people who attended celebrations in Provincetown tested positive for the Delta variant. The health consciousness of this community accounts for the intensive testing and contact tracing that produced the data about infections, who infected whom, and the vaccination status of the people who were infected. Over 70 percent of those who were infected were fully vaccinated. While it's possible that "good" vaccinated people were infected by "bad" unvaccinated people, the meticulous contact tracers would have noted this "bad infecting the good" pattern had it occurred. And they would have called attention to this pattern in their reports. That Delta was spread in Provincetown by the breakthroughs as well as by the unvaccinated is the most plausible explanation; but the mind boggles when confronting the question: how was this possible? More information about the Provincetown cluster can be found in the following news articles:

• "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

Two smaller breakthrough clusters were recently detected in San Francisco, as reported in the following article:

• "More than 200 staff members at 2 San Francisco hospitals have tested positive, most in breakthrough Delta infections.", Eduardo Medina, NY Times, 7/31/21 -- Note: This article describes two large breakthrough clusters, identified via contact tracing and testing, wherein the majority of those who were infected were fully vaccinated

A cluster of breakthroughs was detected on a luxury cruise liner ==>  26 members of the crew and one passenger; all were vaccinated; all had no symptoms or mild symptoms. The cruise line said it randomly tests “a large percentage of our crew on a rotating basis multiple days per week — including more than 900 over the last seven days.”

• "27 people test positive for coronavirus on Carnival cruise ship", Hannah Sampson, Washington Post, 8/13/21

Very high levels of Delta in noses and throats

There were virtually no anecdotal reports of vaccinated people spreading the virus to anyone else when previous variants were dominant, and certainly no reports of large breakthrough clusters. What would cause different outcomes for Delta?

The answer to this question was provided by a stunning new finding reported by the CDC last week. People infected by Delta, both the unvaccinated and the breakthroughs, carry levels of the coronavirus in their noses and throats that are about one thousand times as high as the levels found in the noses and throats of people infected by the original variant -- which makes everyone infected by Delta far more contagious. Here's a link to the CDC report that referenced this finding:

• "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 

Policy implications

Throughout the U.S., vaccinated persons are not routinely tested from time to time except in specific communities, e.g., hospitals, cruise liners, and universities. Contact tracing and testing is also more common in specific communities. These practices have significant implications with regards to the Delta variant:

• The number of Delta breakthrough cases will be grossly underestimated at every level -- community, state, and national. The vaccines still work; they greatly reduce the severity of Delta infections. Only a very small percentage of vaccinated persons will be hospitalized or die. Indeed, most breakthroughs will either be asymptomatic or so mild that the infected individuals may not realize they have been infected, so they won't volunteer to be tested. As consequence, the data about breakthroughs that will usually be compiled at community, state, or national levels will only include the rare breakthroughs that resulted in hospitalizations or deaths.
• The contributions of breakthroughs to surges in the hospitalizations and deaths of unvaccinated persons will be grossly underestimated. Americans are tired of "forever wars". We are tired of the war in Afghanistan against the Taliban, and we are tired of the war in the U.S. against the coronavirus. We distrust the bumbling, flip-flopping CDC; and we grow angrier with each passing day at our friends, neighbors, and coworkers who remain unvaccinated. More than eighteen months into the pandemic, we want our lives to get back to normal -- NOW. So public health officials who expect us to endure six, eight, or ten more months of mitigation are not basing their expectations on any kind of behavioral science or common sense. Given these strong and widely held sentiments among the sixty percent of American adults who are fully vaccinated, public health officials should base their policies on the assumption that growing segments of the vaccinated population will become less and less compliant with restrictive mitigations, and will thereby make larger and larger contributions to future surges of Delta (and more lethal successors) and to increased hospitalizations and deaths among the unvaccinated. Going forward, the only viable public policies for managing the pandemic will involve vaccine mandates. -- "Patience has worn thin’: Frustration mounts over vaccine holdouts", Dan Diamond
   andd Tyler Pager
  
  , Washington Post, 7/24/21 -- "Vaccinated people are ready for normalcy — and angry at the unvaccinated getting in their way", Marisa Iati, Washington Post, 7/31/21 -- "Americans Suffer Pandemic Whiplash as Leaders Struggle With Changing Virus", Sheryl Gay Stolberg and Michael D. Shear, NY Times, 8/2/21

Wikipedia provides a history of vaccine policy in the U.S. that should dispel any readers' misconceptions that opposition to vaccines is unique to COVID; in short, all vaccination mandates for all diseases throughout U.S. history have encountered substantial challenges that required resolution by our courts.

    -- "Vaccination policy in the United States", Wikipedia, Last edit: 16 July 2021

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Related notes on this blog:

• "Downgrading the CDC's guidance", Last update: 7/25/21
  
  
• "Is the Delta variant making masks less effective, but more significant?", Last update: 7/15/21
  
  
• "An open letter to President Biden regarding the critical need to reorganize the CDC immediately", Last update: 6/17/21