CDC Ups SARS-CoV-2 Delta Mutation to "Variant of Concern"

The US Centers for Disease Control and Prevention (CDC) on June 14th, 2021, declared the coronavirus disease 19 (COVID-19) Delta mutation (aka, B.1.617.2) a "variant of concern.” It had previously been classified as a somewhat less concerning “variant of interest.”

The Delta variant, first identified in India in late 2020, now accounts for approximately 10% of new cases of infection in the United States, according to the CDC. In late May, that proportion was only 2.7%. In the United Kingdom, the variant is now responsible for 90% of new infections and has delayed plans to re-open the country by 1 month.

The CDC defines a “variant of concern,” as “a variant for which there is evidence of an increase in transmissibility, more severe disease (eg, increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.”

READ MORE: SARS-CoV-2 Variants: Update on CDC Classifications

“This variant is now identified to be more transmissible than even other hyper transmissible variants like the one from the UK,” CDC Director Rochelle Walensky, MD, said in an interview last week. "We also know that while our vaccines do work against it, they don’t have as much buffer in terms of protection as some of the other wild type strains. So the concern is not just the more transmissibility—and we have seen more virus in the UK where this variant has also emerged—if we have this other variant circulating here it may lead to a more virulent variant such that our vaccines wouldn’t be able to work."

At present, current vaccines appear able to stem the tide against a surge of infections. Research conducted by Public Health England found that the Pfizer vaccine was 88% effective against symptomatic disease from the variant 2 weeks after the second dose, compared to 93% effectiveness against the B.1.1.7 (UK) variant. For the Astra Zeneca vaccine, it was 60% effective against symptomatic disease from the delta variant compared to 66% effectiveness against the B.1.1.7 variant.

According to the World Health Organization, the variant has been reported in 80 countries to date.