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

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.)

Video transcript

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KAVITA PATEL: The Delta variant, previously referred to as B1617.2, believed to be originated from India, is one of the most concerning variants, recently classified by the CDC as a "variant of concern," which means that it is more likely to lead to disease, hospitalizations, and possibly death. And we're already seeing evidence of the Delta variant in the United States.

We believe right now about 7% to 10% of the new cases of COVID-- and we're still having new cases-- are from the Delta variant and that, potentially, over the next two to four weeks, the Delta variant could become the majority variant for new cases of COVID in the United States.

This is a reminder that variants are real. They're unexpected. But we do know they are going to continue to happen as long as we have unvaccinated people in the United States and across the world.

So the Delta variant in comparison to the Alpha variant, which is currently the dominant variant-- and as a reminder, the Alpha variant was previously referred to as the "variant from the UK"-- so that was considered to be one of the most infectious variants that we could have in the world and certainly in the United States.

The Delta variant looks like it might be up to 60% 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.

And so I think, in all contexts, we have to remember this virus continues to mutate. The Alpha variant, which is the dominant one today, will not be the dominant one in two to four weeks. It'll be replaced by the Delta variant, more infectious, more hospitalizations, possibly more deaths.

The good news about the Delta variant is that we believe our currently available vaccines give us protection. The vaccines seem to hold up against the Delta variant. The good news about our current vaccines likely protecting us against all variants, including the Delta variant, is only an emphasis that 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, that after the first dose only that the efficacy or the effectiveness against the Delta variant is in the 30s to 40s versus after two doses having effectiveness that's in the 90s. 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.

We have at least 14 states in which we have pockets of those states that only have 20% to 30% of people vaccinated. And those are potential critical hotspots, and they are the most likely targets for a Delta variant to get widespread infection. And again, it's not just that we will worry about unvaccinated individuals. But as we return to more normal life, school, job, 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.

So it reinforces the bottom line. We need to get the majority of our country vaccinated. We're currently at about 54% who have received one dose. That's not high enough. That means that 46% of our country is still vulnerable and now to a variant that could lead to a worse illness, easier to infect, and potentially a more severe hospitalization, which could translate into more deaths. And I think that's something that's worth remembering when you go out into a population that's not vaccinated.

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