The Delta variant of COVID-19, which originated in India, is the latest challenge the world is facing as key regions struggle to contain the coronavirus pandemic.

The strain is significantly more contagious than any other that's appeared so far, scientists say. It has raised concerns over whether or not the vaccines currently available are effective enough to counter its spread.

Delta now accounts for roughly 30% of cases in the U.S., where 57.2% of adults are fully vaccinated and 66.2% have received at least one dose, according to the latest CDC data.

“We have the potential to have a pandemic within a pandemic,” Dr. Ebony Hilton, an associate professor of anesthesiology and critical care medicine at the University of Virginia, told Yahoo Finance Live in an interview.

“And why is that? Because we know that the vaccine uptake — yes, we’ve crossed over nationally 70% of all adults over 30 being vaccinated. But we know that’s not consistent across our country,” she added.

Many states have crossed the 70% threshold that allowed for their economies to fully reopen. But other parts of the country, including many states in the South, are struggling to convince their residents to get the vaccine.

This has led to an uptick in cases because the more time a virus has to circulate, the more opportunities it gets to mutate, such as the case with the Delta variant.

“We know that mutants, or mutations of the virus, come about because the virus is allowed to pass from person to person,” Hilton said. “The way we stop that passing from person to person is through vaccination.”

Nearly all of the Northeast are among the top 10 states with the most vaccinated residents. Conversely, states like Mississippi, Louisiana, Alabama, and Wyoming have yet to cross the 50% threshold. Much of this has correlated to outbreaks the country is seeing among those unvaccinated.

“We know the Northeast is doing a fantastic job,” Hilton said. “But down South, we are having vaccine hesitancy show up. And at the same time there’s vaccine hesitancy, we’re having an increase in our Delta variant."

She added that although U.S. cases have dropped 21% overall, parts of the South and Midwest are in the throes of double-digit case spikes.

'This Delta variant is a game changer'

There are numerous reasons why many Americans are still unvaccinated.

Fears over side effects from the dose are among the most common. There have been recent reports indicating that the vaccine has been linked to a small number of cases of myocarditis, a type of heart infection.

But according to Hilton, the benefits of the vaccine far outweigh the risks.

“When we’re weighing the risk benefits of vaccination versus COVID-19, what we know is that persons with COVID-19 have also presented with myocarditis or pericarditis, which is the inflammation of the muscle or inflammation of the lining of the heart,” she said.

There have been 12.6 cases of myocarditis per million second COVID-19 doses administered, which is a .00126% occurrence. In comparison, a study from the Journal of the American Medical Association (JAMA) found that among 1,597 U.S. college athletes who tested positive for COVID-19, 2.3% experienced myocarditis.

“What we do know is that these persons typically have mild symptoms as far as myocarditis,” Hilton said of those adversely affected by the vaccine. “And they respond to medications, like anti-inflammatories and steroids, for instance. I would not at this time tell people to hesitate to get vaccinated.”

Hilton noted that a friend of hers who was vaccinated back in February recently tested positive for COVID-19, despite taking major precautions. The friend experienced just minor symptoms, but Hilton stressed that the risk is still prevalent nonetheless because of the Delta variant.

“This Delta variant is a game changer,” she said. “It does have the potential for us to see a pandemic within a pandemic. So we can’t let our guards down … COVID-19 is still taking at least 400 people’s lives a day.”

Adriana Belmonte is a reporter and editor covering politics and health care policy for Yahoo Finance. You can follow her on Twitter @adrianambells and reach her at [email protected].

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