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The new SARS-CoV-2 variant first appearing in southern England has a transmission advantage of 0.4 to 0.7 points higher in reproduction number, also known as R0, compared to the initial strain, British researchers found.

This variant, called 202012/01, has a "substantial transmission advantage," meaning its reproduction numbers could vary from 1.4 to 1.8, according to a multi-disciplinary team based at Imperial College London (ICL), who on the school's website.

Led by ICL's Erik Volz, PhD, the team found a "large and statistically significant imbalance" in regions where incidence of the variant increased and incidence of the non-variant decreased, and vice versa, which would indicate a change in R0.

Volz and colleagues also noted a larger share of individuals under age 20 among reported cases of the variant versus non-variant cases, dubbing this "a shift in age composition." They estimated that the variant's R0 is .

For context in the U.S., prior research found seasonal influenza had a of 1.28, while the median reproduction number for the 1918 flu pandemic was 1.80.

This variant already traveled across the pond, with a Colorado man as the last week, though reports of the variant cropped up in other states over the holiday, and .

CDC officials briefed reporters about the variant on Wednesday, noting it appears unlikely to impact COVID-19 vaccine effectiveness, though it may render certain treatments less effective, such as convalescent plasma. The agency says it expects more data on the variant soon.

A preliminary report from the U.K.'s Centre for Mathematical Modelling of Infectious Diseases on Dec. 23 originally estimated transmission may be at least 56% and up to 70% higher. They on Dec. 31, noting the frequency of the variant "has grown substantially in all regions of England," with a 50% or greater frequency in all National Health System regions.

The Imperial College group examined both epidemiological and genetic data, including 1,904 whole genomes from October and December 5 with a genetic background of 48,128 genomes collected over the same period. Notably, they found a "high correlation" between S-gene target failure (SGTF) during COVID-19 PCR testing and frequency of the variant, meaning S-gene target failure could act as a biomarker to detect the variant in the community.

"We see a very clear visual association between SGTF frequency and epidemic growth in nearly all areas ... which is reinforced by empirical assessment of area-specific week on week growth factors of [variant] and non-[variant] case numbers," Volz and colleagues wrote.

They noted a "small, but significant" shift towards individuals under age 20 being more affected by the variant, even after adjusting for several confounders. Any number of factors could account for this: an overall increase in transmissibility of the variant, younger people being more susceptible, or greater symptomatology with the variant.

The group warned that while further research is needed, a variant with increased transmissibility indicates increased public health measures may be needed to contain the virus.

"Social distancing measures will need to be more stringent than they would have otherwise. A particular concern is whether it will be possible to maintain control over transmission while allowing schools to reopen," the group wrote.

But there continues to be no indication that the variant will resist vaccine-mediated immunity, or that it's more lethal, except to the extent that hospitals become more overburdened with cases and thus less able to provide high-level care to every patient.

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