What Was the Lambda SARS-CoV-2 Variant?

Lambda was a "variant of interest" between June 2021 and March 2022.

While people in the US faced the Delta variant, another variant of SARS-CoV-2 (the virus that causes COVID-19) emerged. C.37, dubbed the Lambda variant, was reported in multiple countries, mainly in South America.

On March 9, 2022, the World Health Organization (WHO) designated Lambda as a previous variant of interest (VOI), meaning it no longer posed "a major added risk to global public health compared to other circulating SARS-CoV-2 variants."

Here's more on what that means, and what we know about the Lambda variant as of September 2022.

What Is a Variant of Interest (VOI)?

The WHO considers a SARS-CoV-2 variant a VOI when it meets the following two criteria:

  • The variant has genetic changes that can affect certain virus characteristics, including transmissibility and COVID-19 disease severity.
  • The variant has been identified to "cause significant community transmission or multiple COVID-19 clusters." It has spread to multiple countries with an increasing number of cases, enough to suggest it's an "emerging risk to global public health."

A variant that no longer meets both criteria is called a "previously circulating VOI." As of Sept. 22, 2022, there were no circulating VOIs anywhere in the world, according to the WHO.

A SARS-CoV-2 variant can also meet a more "severe" designation of a variant of concern (VOC). That means it meets the VOI criteria, plus demonstrates one or more "changes at a degree of global public health significance." For example, a VOC may decrease the effectiveness of available public health measures, diagnostics, and vaccines.

As of Sept. 22, 2022, Omicron was the only circulating VOC.

Where Did the Lambda Variant Spread?

The WHO designated Lambda as a VOI on June 14, 2021. Lambda was named a "previous VOI" on March 9, 2022, meaning it no longer posed enough of a risk to be a VOI. The variant was never upgraded to a VOC.

Lambda was first reported in Peru in August 2020. It spread rapidly, mainly through Chile, Peru, and Argentina. Between April and mid-June, 2021, 81% of COVID-19 cases in Peru were associated with Lambda, per a June 15, 2021, WHO update.

Other countries in the region—Ecuador, Colombia, Brazil, Venezuela, and Bolivia—didn't experience widespread cases of Lambda. At the time, these countries were more affected by other SARS-CoV-2 variants, per a June 2022 paper in the Journal of Medical Virology.

European countries were also less affected by Lambda, though the June 2022 paper found some local outbreaks of the variant. Oceanian, African, and Asian countries documented even fewer cases.

Covid-Variant-Lambda-AdobeStock_325887897
AdobeStock / Jo Imperio

Are COVID-19 Vaccines Effective Against Lambda?

Lambda may be slightly resistant to COVID-19 vaccines, but they are still effective against the virus. A December 2021 paper published in the journal Emerging Microbes & Infections noted that the Lambda variant "may not have a significant impact on the protective effect of current vaccines."

And mRNA vaccines (such as Pfizer and Moderna) may be the best option. According to a February 2022 paper published in the Cardiology Journal, Lambda could be neutralized by mRNA vaccines with a "relatively small" reduction in the amount of vaccine-induced antibodies in the blood.

Should People in the US Worry About the Lambda Variant?

As of September 2022, the answer is "no." The June 2022 paper said Lambda wasn't "epidemiologically relevant" in North America or Europe, meaning scientists in those areas didn't need to actively track the variant.

SARS-CoV-2 variants in the US are routinely monitored by the Centers for Disease Control and Prevention (CDC). As of April 26, 2022, the CDC wasn't monitoring the Lambda variant (and Omicron was the only VOC).

That said, by September 2022, COVID-19 had not been eradicated in the US. The CDC still recommended prevention actions to protect you and others from getting sick, including staying up-to-date on COVID-19 vaccines, getting tested when needed, staying home if you're sick, and wearing masks in communities with higher COVID-19 levels (as designated by the CDC).

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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