The delta variant of the coronavirus appears to cause more severe illness than earlier variants and spreads as easily as chickenpox, according to an internal
federal health document that argues officials must “acknowledge the war has changed.”
The document is an internal Centers for Disease Control and Prevention slide presentation, shared within the CDC and obtained by The Washington Post. It captures
the struggle of the nation’s top public health agency to persuade the public to embrace vaccination and prevention measures, including mask-wearing, as cases surge across the United States and
new research suggests vaccinated people can spread the virus.
The document strikes an urgent note, revealing the agency knows it must revamp its public messaging to emphasize vaccination as the best defense against a variant
so contagious that it acts almost like a different novel virus, leaping from target to target more swiftly than Ebola or the common cold.
It cites a combination of recently obtained, still-unpublished data from outbreak investigations and outside studies showing that vaccinated individuals infected
with delta may be able to transmit the virus as easily as those who are unvaccinated.
The data and studies cited in the document played a key role in revamped recommendations that call for everyone — vaccinated or not — to wear masks indoors in
public settings in certain circumstances, a federal health official said.
That official told The Post that the data will be published in full on Friday. CDC Director Rochelle Walensky privately briefed members of Congress on Thursday,
drawing on much of the material in the document.
One of the slides states that there is a higher risk among older age groups for hospitalization and death relative to younger people, regardless of vaccination
status. Another estimates that there are 35,000 symptomatic infections per week among 162 million vaccinated Americans.
The document outlines “communication challenges” fueled by cases in vaccinated people, including concerns from local health departments about whether coronavirus
vaccines remain effective and a “public convinced vaccines no longer work/booster doses needed.”
The presentation highlights the daunting task the CDC faces. It must continue to emphasize the proven efficacy of the vaccines at preventing severe illness and
death while acknowledging milder breakthrough infections may not be so rare after all, and that vaccinated individuals are transmitting the virus. The agency must move the goal posts of success
in full public view.
“Although it’s rare, we believe that at an individual level, vaccinated people may spread the virus, which is why we updated our recommendation,” according to the
federal health official, who spoke on the condition of anonymity because they were not authorized to speak publicly.
“Waiting even days to publish the data could result in needless suffering and as public health professionals we cannot accept that.”
The presentation came two days after Walensky announced the reversal in guidance on masking among people who are vaccinated. On May 13, people were told they no
longer needed to wear masks indoors or outdoors if they had been vaccinated. The new guidance reflects a strategic retreat in the face of the delta variant. Even people who are vaccinated should
wear masks indoors in communities with substantial viral spread or when in the presence of people who are particularly vulnerable to infection and illness, the CDC said.
The document presents new science but also suggests a new strategy is needed on communication, noting that public trust in vaccines may be undermined when people
experience or hear about breakthrough cases, especially after public health officials have described them as rare.
Matthew Seeger, a risk communication expert at Wayne State University in Detroit, said a lack of communication about breakthrough infections has proved problematic.
Because public health officials had emphasized the great efficacy of the vaccines, the realization that they aren’t perfect may feel like a betrayal.
“We’ve done a great job of telling the public these are miracle vaccines,” Seeger said. “We have probably fallen a little into the trap of over-reassurance, which
is one of the challenges of any crisis communication circumstance.”
The CDC’s revised mask guidance stops short of what the internal document calls for. “Given higher transmissibility and current vaccine coverage, universal masking
is essential to reduce transmission of the Delta variant,” it states.
The document makes clear that vaccination provides substantial protection against the virus. But it also states that the CDC must “improve communications around
individual risk among [the] vaccinated” because that risk depends on a host of factors, including age and whether someone has a compromised immune system.
The document includes CDC data from studies showing that the vaccines are not as effective in immunocompromised patients and nursing home residents, raising the
possibility that some at-risk individuals will need an additional vaccine dose.
The agency faced criticism from outside experts this week when it changed the mask guidance without releasing the data, a move that violated scientific norms, said
Kathleen Hall Jamieson, director of the Annenberg Public Policy Center at the University of Pennsylvania.
“You don’t, when you’re a public health official, want to be saying, ‘Trust us, we know, we can’t tell you how,’” Jamieson said. “The scientific norm suggests that
when you make a statement based on science, you show the science. … And the second mistake is they do not appear to be candid about the extent to which breakthroughs are yielding
The breakthrough cases are to be expected, the CDC briefing states, and will probably rise as a proportion of all cases because there are so many more people
vaccinated now. This echoes data seen from studies in other countries, including highly vaccinated Singapore, where 75 percent of new infections reportedly occur in people who are partially and
Walter A. Orenstein, associate director of the Emory Vaccine Center, said he was struck by data showing that vaccinated people who became infected with delta shed
just as much virus as those who were not vaccinated. The slide references an outbreak in Barnstable County, Mass., where vaccinated and unvaccinated people shed nearly identical amounts of
“I think this is very important in changing things,” Orenstein said.
A person working in partnership with the CDC on investigations of the delta variant, who spoke on the condition of anonymity because they were not authorized to
speak, said the data came from a July 4 outbreak in Provincetown, Mass. Genetic analysis of the outbreak showed that people who were vaccinated were transmitting the virus to other vaccinated
people. The person said the data was “deeply disconcerting” and a “canary in the coal mine” for scientists who had seen the data.
If the war has changed, as the CDC states, so has the calculus of success and failure. The extreme contagiousness of delta makes herd immunity a more challenging
target, infectious-disease experts said.
“I think the central issue is that vaccinated people are probably involved to a substantial extent in the transmission of delta,” Jeffrey Shaman, a Columbia
University epidemiologist, wrote in an email after reviewing the CDC slides. “In some sense, vaccination is now about personal protection — protecting oneself against severe disease. Herd
immunity is not relevant as we are seeing plenty of evidence of repeat and breakthrough infections.”
Kathleen Neuzil, a vaccine expert at the University of Maryland School of Medicine, said getting more people vaccinated remains the priority, but the public may
also have to change its relationship to a virus almost certain to be with humanity for the foreseeable future.
“We really need to shift toward a goal of preventing serious disease and disability and medical consequences, and not worry about every virus detected in somebody’s
nose,” Neuzil said. “It’s hard to do, but I think we have to become comfortable with coronavirus not going away.”