What differences are there between the covid-19 lambda and delta variants?

The US is in the grip another wave of covid-19 infections driven by the highly contagious Delta covid-19 variant. Nearly every state in the US is seeing an increase in new cases, especially areas with low vaccination rates.

The Delta variant isn’t alone in the US, although it now represents 93 percent of new cases around the country after displacing the previously dominant variant Alpha. Another covid-19 variant Lambda, which first appeared in Peru last year and has spread around South America, is also considered highly contagious and could potentially get past the protection the covid-19 vaccines provide. So how do the two compare?

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What are the characteristics of the Delta and Lambda variants?

Early studies suggest that Lambda, like the Delta variant, has mutations that make it more transmissible than the original strain of the coronavirus. There is also concern that both could bypass the protection that vaccines provide. However, "at the moment, the vaccine remains protective against serious infection," Michel Nussenzweig coauthor of a recent study on the evolution of covid-19 antibodies after vaccination.

Although still rare, breakthrough cases of people who are vaccinated getting infected with the Delta variant have been reported. Researchers analyzing viral loads on nose-and-throat swab samples taken in Wisconsin found similar viral loads in vaccinated and unvaccinated patients. A separate study out of Singapore had similar findings, however the viral loads decreased faster in the vaccinated group.

This could allow even the vaccinated to shed the virus and infect others, which has led the CDC to recommend face coverings indoors in areas of “high” or “substantial” transmission, a condition present in almost 90 percent of the US according to CDC data.

“Variant of interest”

The WHO has listed the Lambda strain a “variant of interest” which is a classification which suggests it is “an emerging risk to global public health.” This happens when a variant has “genetic changes that are predicted or known to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape.” Included in this category are the variants Eta, Iota and Kappa. The CDC currently hasn’t classified the Lambda variant.

The Delta strain is in the highest listing considered a “variant of concern”. Also included in this listing are the Alpha, Beta and Gamma strains.

Delta vs. Lambda

The US is the country with the third highest number of Lambda covid-19 variant cases, behind Chile and Peru. Genomic sequencing has identified 846 cases of covid-19 caused by the Lambda variant in the US so far, according to the independent data-sharing initiative GISAID. There are 32 countries which have reported at least 1 lambda case to GISAID.

This is a far cry from the 131 countries reporting cases of the Delta covid-19 variant, with the US reporting over 122,000 cases, less than half the number reported in the United Kingdom. However, the Delta strain has had more time to move around the US than the Lambda strain. The first cases were reported in July, but a sequencing sample from South Carolina indicates that it has been in the US since April.

For now though, it appears that the Lambda variant can’t compete with the Delta variant according to data posted in a tweet from Eric Topol, a professor of molecular medicine at Scripps Research.