How much more transmissible is the new variant of the coronavirus?

The new variant of SARS-CoV-2 that first appeared in the south of England has a 0.4 to 0.7 point higher transmission advantage in breeding number, also known as R0, compared to the original strain, discovered British researchers.

This variant, called 202012/01, has a “substantial transmission advantage,” meaning its breeding numbers could range from 1.4 to 1.8, according to a multidisciplinary team based at Imperial College London (ICL ), who published his findings on the school. website.

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

Volz and his colleagues also noted a greater proportion of individuals under the age of 20 among reported cases of the variant compared to non-variant cases, calling it “a change in age composition.” They estimated that the R0 of the variant is 40 to 80% higher than that of the wild type virus.

For the US context, previous research found that seasonal flu had a median reproduction number of 1.28, while the median reproduction number for the 1918 influenza pandemic was 1.80.

This variant has already crossed the pond, with a man from Colorado as the first documented case in the United States last week, although reports of the variant were reported in other states during the holidays, including California and Florida.

CDC officials briefed reporters on the variant on Wednesday, noting that it appears unlikely to have an impact on the effectiveness of the COVID-19 vaccine, although it may make some treatments less effective, such as convalescent plasma. The agency says it is expecting more data on the variant soon.

A preliminary report from the UK Center for the Mathematical Modeling of Infectious Diseases on December 23 initially estimated that transmission could be at least 56% and up to 70% higher. They updated their results on December 31, noting that the frequency of the variant “has increased significantly in all parts of England”, with a frequency of 50% or more in all regions of the national health system.

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

“We are seeing a very clear visual association between the frequency of SGTF and epidemic growth in almost all areas … which is reinforced by an empirical assessment of area-specific weekly growth factors. [variant] and no-[variant] case numbers, ”Volz and colleagues wrote.

They noted a “small but significant” change towards those under 20 who were most affected by the variant, even after adjusting for several confounding factors. Any number of factors could explain this: an overall increase in the transmissibility of the variant, the young being more susceptible, or a greater symptomatology with the variant.

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

“Social distancing measures will need to be stricter than they otherwise would have been. Of particular concern is whether it will be possible to maintain control over transmission while still allowing schools to reopen,” wrote the group.

But there is still no indication that the variant will resist vaccine-mediated immunity, or that it is more lethal, except to the extent that hospitals become more overloaded with cases and therefore less able to provide high-level care to patients. each patient.