The dominant Delta variant's ability to efficiently infect people and rapidly grow inside a person is enabling the coronavirus to regain its footing in the United States.

Why it matters: "The solution is right in front of us — get everybody vaccinated and we wouldn't even be talking about this," NIAID director Anthony Fauci tells Axios.

Driving the news: The CDC said the "war has changed" under the Delta variant of SARS-CoV-2, which went from about 3% of all strains a few months ago to now being close to 90%, Fauci says.

• The CDC said Delta may be just as contagious or more contagious than chickenpox, smallpox, MERS, SARS, Ebola, the 1918 flu, the seasonal flu, and the common cold, per internal documents the Washington Post was first to publish.

What's happening: Delta has become "an incredibly efficient spreader from human to human" that binds easier to the cell receptors in the upper airway after it enters the body, replicates more quickly and transmits more readily, Fauci says.

• "When you look at the level of virus in the nasal pharynx of an infected person with Delta, and you compare it to the level of virus in the nasal pharynx of somebody with the Alpha variant, it's sometimes as high as 1,000 times more virus," Fauci says.
• Julie Fischer, senior technical adviser for global health for CRDF Global, says the pandemic has "entered a new phase" where a higher vaccination rate plus more masking and social distancing in certain areas will be required to stop the spread of COVID-19.
• Ezekiel Emanuel, vice provost for global initiatives at the University of Pennsylvania, stressed the importance at an ISDA briefing Tuesday of good indoor ventilation and using NIOSH-approved masks even in outdoor areas that are crowded.

Details: The "effective reproductive rate," or how many people are still susceptible from one infected person after taking into account the mitigating effects of immunity and vaccinations, has jumped due to the Delta variant," Fisher says.

• It has gone from below 1 person just a couple of months ago to around 4 to 5 people in communities with 50% or lower vaccination coverage, she says.
• Recent studies also suggest the Delta variant causes a greater degree of severe complications and hospitalizations, although more data is needed, Fauci adds.
• There are also some indications vaccinated people may still be able to transmit the virus, but those numbers are low when you look at the overall number of vaccinated people, Fauci says. And vaccines are "doing what they're supposed to do" and "preventing you from getting seriously sick," he adds.

Between the lines: Resistance to vaccinationis a serious, multifaceted problem, Fauci says, "ranging from needing a bit more information to waiting until the FDA approves to ideological differences."

• Public health officials are trying to reach out via trusted messengers in the community, ranging from local doctors to community leaders, pastors and sports figures, as well as using new platforms like Instagram, he says.
• Fauci says he's also hopeful some may be encouraged to vaccinate once the FDA gives its final approval — which he hopes will happen by mid-August after the agency has completed its regular evaluation process. The New York Times reported the Pfizer-BioNTech vaccine is expected to be approved by Labor Day.

Yes, but: The timing of Delta is particularly concerning because people are fatigued and schools are about to start, Fischer says.

• "Delta changes the dynamic of responding to the pandemic again," Fischer says. "There has been sort of a complacency in the U.S. that children are not at high risk of severe disease, but I think we're hearing from the communities where there is widespread community transmission of the Delta variant that there are children becoming severely ill."

What's next: U.S. public health officials are closely watching Delta's growing sublineages, AY.1, AY.2 and AY.3, or so-called Delta Plus.

• "We don't know right now if those other sublineages are going to make Delta even worse than it is. It doesn't look like that's the case, but we don't know," Fauci says.

The bottom line: Some people may be disturbed by changed recommendations from the CDC, Fischer says, "but it's important for people to understand what's changed is not the tools that we have. ... What's changed is the virus."

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