There’s some news about the study that purports to explain why the CDC changed its mask recommendations to saying that even vaccinated people need to wear masks indoors in higher-COVID areas. Here’s a link to the actual study results.
I noticed a couple of interesting things on reading it. The first is that it’s a single study set in Barnstable County, Massachusetts after a series of July 4th holiday celebrations that drew many people to outside and inside venues in order to celebrate. The second is that almost all the COVID patients were male, and the median age was 42. That struck me as atypical (especially the huge male skew). But knowing the Cape somewhat it doesn’t take but a moment to realize that Barnstable County is dominated by Provincetown, which in turn is highly gay-friendly and has long been a center of gay culture. So of course the population there for the holidays is going to be heavily male and perhaps younger than typical in most towns. This may not matter at all in terms of the study’s results, but it’s a somewhat atypical population and that should be noted.
This is of interest:
The findings in this report are subject to at least four limitations. First, data from this report are insufficient to draw conclusions about the effectiveness of COVID-19 vaccines against SARS-CoV-2, including the Delta variant, during this outbreak. As population-level vaccination coverage increases, vaccinated persons are likely to represent a larger proportion of COVID-19 cases. Second, asymptomatic breakthrough infections might be underrepresented because of detection bias. Third, demographics of cases likely reflect those of attendees at the public gatherings, as events were marketed to adult male participants; further study is underway to identify other population characteristics among cases, such as additional demographic characteristics and underlying health conditions including immunocompromising conditions…Finally, Ct values obtained with SARS-CoV-2 qualitative RT-PCR diagnostic tests might provide a crude correlation to the amount of virus present in a sample and can also be affected by factors other than viral load.††† Although the assay used in this investigation was not validated to provide quantitative results, there was no significant difference between the Ct values of samples collected from breakthrough cases and the other cases. This might mean that the viral load of vaccinated and unvaccinated persons infected with SARS-CoV-2 is also similar. However, microbiological studies are required to confirm these findings.
So if I’m interpreting this correctly, the study didn’t directly measure viral load, but the researchers concluded from Ct values (see this for an explanation of what a Ct value is) that there might be a correlation with viral loads.
Note also point number three, which I’ll repeat here:
Third, demographics of cases likely reflect those of attendees at the public gatherings, as events were marketed to adult male participants; further study is underway to identify other population characteristics among cases, such as additional demographic characteristics and underlying health conditions including immunocompromising conditions.
They don’t say exactly what they’re talking about, but reading between the lines I infer that they are talking about gay men and the possibility of “immunocompromising conditions” such as AIDS, HIV, or medication for either of those things. None of this reflects on gay people themselves, but I question whether it’s wise to extrapolate from a single study at all, and certainly from one involving a particular demographic that is very possibly atypical in relevant ways such as immune status.
Other interesting findings include this: “Among persons with breakthrough infection, 274 (79%) reported signs or symptoms, with the most common being cough, headache, sore throat, myalgia, and fever” – in other words, basic flulike symptoms. Only five people were hospitalized (four of them vaccinated) and none died. So the hospitalization rate in a symptomatic population (which was almost certainly not everyone infected) was about one and a half percent among symptomatic breakthrough patients, which does not seem at all high. The death rate so far is zero.
It was always stated that between 5 and 10 percent of vaccinated people were vulnerable to getting COVID, depending on the type of immunization used. So these figures alone don’t seem to justify what the CDC is doing. It would be helpful to also know how many people attended the festivities, but all I’ve read is “thousands.” That covers a lot – could be a few thousand or hundreds of thousands. Without knowing that, we can’t know what the infection rate was among the unvaccinated or the vaccinated, and whether either was higher than expected or about what might be expected.
