The COVID-19 Delta variant: What you need to know


A colourised scanning electron micrograph of a cell (purple) infected with SARS-CoV-2 particles (green), isolated from a patient sample

This week, the Centers for Disease Control and Prevention officially declared the Delta variant, a coronavirus strain first detected in India, "a variant of concern." This designation is given to variants shown to be more transmissible than the original strain, that can cause more severe disease and potentially reduce the effectiveness of treatments or vaccines.

Yahoo News Medical Contributor Dr. Kavita Patel, a primary care physician in Washington, D.C., who also serves as a health policy fellow at the Brookings Institution, answered some questions about the Delta variant, which some experts have called "the most troubling variant by far." (Some answers have been edited for clarity.)

Why was the Delta variant classified as a variant of concern?

The Delta variant, also referred to as B.1.6.1.7.2 [and] believed to have originated from India, is one of the most concerning variants It is more likely to lead to disease, hospitalizations and possibly death.

The Delta variant looks like it might be up to 60 percent more infectious, which is why the CDC really put a bold label forward in calling it a variant of concern. They only do that when they think a variant is concerning enough that it could change the course of a disease or potentially pose a threat to someone who gets it.

What percentage of U.S. infections can currently be traced to the Delta variant?

We're already seeing evidence of the Delta variant in the United States. We believe right now about seven to 10 percent of the new cases of COVID are from the Delta variant and that potentially over the next two to four weeks, the Delta variant could become the dominant variant for new cases of COVID in the United States.

Do COVID-19 vaccines work against the Delta variant?

The good news is that we believe our currently available vaccines give us protection. They seem to hold up against the Delta variant.

You need to get the full doses of those vaccines. For the two dose vaccines — Pfizer and Moderna — the initial studies, especially from Pfizer, show that you really do need not just the first but the second dose as well, to get the full protection. After the first dose the efficacy or the effectiveness against the Delta variant is in the thirties to forties [percent] versus after two doses having effectiveness that's in the nineties. So it is critical to make sure that people get both doses of any two dose vaccines or at least the one dose of the Johnson & Johnson vaccine.

Could this variant pose serious risk for states lagging in COVID-19 vaccinations?

We have at least 14 states in which we have pockets of those states that only have 20 percent to 30 percent of people vaccinated. Those are potential critical hot spots, and they are the most likely targets for a Delta variant to become widespread infection. And it's not just that we will worry about unvaccinated individuals, but as we return to more normal life — school, workplace — and you have vaccinated and unvaccinated people mixing, you have a higher potential come fall for breakthrough infections, a higher potential for immune escape and a higher potential for new variants, which threaten even currently vaccinated people.

We're currently at about 54 percent [of the U.S. population] who have received one dose. That's not high enough. That means that 46 percent of our country is still vulnerable. And now to a variant that could lead to a worse illness, it's easier to infect, and potentially lead to more hospitalizations, which could translate into more deaths. I think that's something worth remembering when you go out into a population that's not vaccinated.

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