https://reason.com/2021/07/30/the-provincetown-outbreak-shows-vaccinated-people-can-be-infected-by-the-coronavirus-but-the-cdcs-director-grossly-exaggerates-that-risk/
"Every 20 vaccinated people, one or two of them could get a breakthrough infection," Walensky told CNN's John Berman. That statement, which implies that 5 to 10 percent of vaccinated people will catch COVID-19, grossly exaggerates the odds of a breakthrough infection. Walensky seems to have misconstrued the meaning of the effectiveness rates reported in vaccine studies, which is a pretty serious mistake for the head of the CDC to make.
When a vaccine is described as 90 percent effective against infection, that does not mean 10 percent of vaccinated subjects were infected. Rather, it means the risk of infection among vaccinated people was 90 percent lower than the risk among unvaccinated people. As the CDC noted on Tuesday, when it issued its revised mask guidance, post-approval studies of COVID-19 vaccines typically have found that they reduce the risk of infection by 86 percent to 99 percent. That means the odds of a breakthrough infection were much lower than Walensky suggested on CNN.
In one U.S. study of adults who had received the Pfizer or Moderna vaccines, for example, the incidence of positive COVID-19 tests among fully vaccinated subjects was 0.048 per 1,000 person-days, compared to 0.43 per 1,000 person-days among the unvaccinated controls, yielding an effectiveness rate of 89 percent. A study of U.S. health care workers put the incidence of infection at 1.38 per 1,000 person-days when the subjects were unvaccinated, compared to 0.04 per 1,000 person-days when they were fully vaccinated, yielding an effectiveness rate of 97 percent. In both cases, the risk of a breakthrough infection was at least an order of magnitude lower than the 5-to-10-percent estimate that Walensky offered.
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Last spring, the misconception that seems to underlie Walensky's risk estimate generated an erroneous CNN story that claimed vaccinated air travelers face a 10 percent risk of infection. Confusion about vaccine effectiveness rates continues to show up in press coverage of COVID-19. Yesterday NPR quoted Kathleen Neuzil, director of the Center for Vaccine Development and Global Health at the University of Maryland, as saying that "even with a 95% efficacious vaccine, you will have one in 20 vaccinees who are exposed get the disease."
I emailed Neuzil about that statement, which is similar to what Walensky said on CNN. "I was actually misquoted on that one," Neuzil said, "and you are the first one to pick up on it (or at least reach out to me about it!). Sometimes in simplifying we don't get the message right. The bottom line is that vaccine isn't 100% protective, and even at high levels of protection we will have breakthrough."
That bottom line is certainly correct. But in warning people about that possibility, public health officials like Walensky should not distort the underlying science by implying the risk is much bigger than the evidence indicates. This episode is reminiscent of Walensky's hyperbole about the risk of outdoor COVID-19 transmission, which misrepresented the study she cited in several significant ways.
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*shrug* oops! *shrug*
Guess it’s too much to ask that the director of the CDC communicate risk to the American people in an articulate, honest, and accurate way.
It’s only, ya know, ******* central to what they’re supposed to do.