Although scientists are concerned about the increased transmissibility of the delta variant, as well as its potential to lead to more dangerous mutations, many are cautiously optimistic that it won't lead to the "doomsday" scenario some anticipate. Here's what you need to know about the delta variant now—and what it means for the pandemic going forward.

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Concern about delta and other variants

Last week, an internal CDC document, based on published and unpublished data, suggested that the delta variant is more contagious than several common viruses—including MERS, SARS, the common cold, influenza, and smallpox—and that vaccinated individuals infected with the delta variant carry similar amounts of viral load as those who are unvaccinated.

The increased transmissibility of the delta variant has been a particular cause of concern for public health officials, with the data from the CDC document describing "a variant so contagious that it acts almost like a different novel virus," according to the Washington Post. And, in states with low vaccination rates, such as Arkansas, Florida, Nevada, and Missouri, this increased transmissibility has allowed the delta variant to spread rapidly and cause several Covid-19 outbreaks, STAT News reports.

According to The Hill, scientists are also concerned that the virus that causes Covid-19 may mutate into even more transmissible variants because of the rapidly spreading delta variant—which itself contains several mutations.

While mutations are not guaranteed to happen, the chances of them occurring remain high given that "such a large number of people" in the United States do not have even one vaccine dose, The Hill reports. And any potential mutation could result in a variant even more virulent than delta—including one or several that are able to bypass the currently available vaccines.

"Right now, fortunately, we are not there," CDC Direct Rochelle Walensky said. "These vaccines operate really well in protecting us from severe disease and death. But the big concern is that the next variant that might emerge, just a few mutations potentially away, could potentially evade our vaccines."

Separately, Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, noted that the mutations in the current variants indicate that the coronavirus' evolution is not incorporating alterations that are "completely resistant" to current vaccines.

"I'm hoping what that means is that we won't see a doomsday Covid-19 that's completely resistant to all of our vaccines," he said. "I don't think that's gonna happen."

However, Andrew Pekosz, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, said it is "incredibly difficult" to predict when harmful mutations to the coronavirus will occur, but that there will be more opportunities for mutations in places where the virus spreads easily.

"Until we make sure that the virus can't freely replicate in the population anywhere in the world, we're always going to have that increased likelihood of mutations occurring," Pekosz said.

How are people faring against the delta variant?

Ultimately, The Hill reports, public health officials believe "immediate" vaccination is the best way to curb the risk of more virulent mutations developing.

"Now is the time for people to get vaccinated," Rachel Levine, HHS's assistant secretary for health, said. "That's the best way to protect against the development of these variants."

For instance, although vaccinated people infected with the delta variant may carry similar viral loads as do unvaccinated people, those who are vaccinated are likely to be contagious for less time, STAT News reports—which means that they will infect fewer people on average.

In addition, according to STAT News, even though the delta variant continues to account for more breakthrough infections among vaccinated people than do other variants, people who are vaccinated are still substantially less likely overall to be infected with the delta variant than those who are not vaccinated.

For example, CDC data has found that symptomatic breakthrough infections are generally rare, occurring in roughly 0.098% of those who are fully vaccinated. And severe breakthrough infections remain exceedingly rare, according to the White House Covid-19 Task Force, with the vast majority (97%) of hospitalized Covid-19 patients being unvaccinated. Deaths from Covid-19 have also not experienced a rapid jump despite spikes in new cases, primarily because the majority of older adults, who make up the most vulnerable population, have been fully vaccinated.

'You have a responsibility,' Fauci says

Ultimately, public health officials are hopeful—although far from certain—that the surge in cases and hospitalizations from the delta variant could fade over time based on what has happened in other countries, STAT News reports.

For instance, in the United Kingdom, a surge caused by the delta variant that began in mid-May hit its peak in mid-July and has since rapidly declined, a drop some experts have chalked up to coronavirus countermeasures, vaccinations, and changes in human behavior.

And federal officials in the United States so far have said they do not currently anticipate implementing a nationwide vaccine mandate or return to the lockdown measures that were in place in 2020.

"I don't think we're gonna see lockdowns," Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said on Sunday. "I think we have enough of the percentage of people in the country—not enough to crush the outbreak—but I believe enough to not allow us to get into the situation we were in last winter."

However, Fauci added that "things are going to get worse" with the current delta variant surge, and he underscored the need for all people to follow recommended safety guidance, such as CDC's revised masking protocols. "It's not only impacting you. And you've got to think about it, that you are a member of society and you have a responsibility," he said. (Coleman, The Hill, 7/31; Joseph, STAT News, 7/30; Reyes, Axios, 8/1; Williams, The Hill, 7/31)