Despite the growing spread of the lambda coronavirus variant across the United States, experts say they're not nearly as concerned about lambda as they are the delta variant—largely because lambda has been moving slowly and vaccines remain very effective against it.
The lambda variant was first identified in Peru in December 2020, where it accounted for 81% of cases between mid-April and mid-June. Since it was identified, the variant has been spotted in at least 29 countries, including several nations in Latin America—including Argentina, Chile, and Ecuador—as well as the United States and Britain.
On June 14, the World Health Organization labeled lambda a "variant of interest," one step below a "variant of concern." Meanwhile, Britain on June 23 labeled lambda a "variant under investigation," citing its "international expansion" as well as its "novel combination of mutations."
According to a preprint study published in BioRxiv, the lambda variant has novel mutations on the receptor binding domain of the virus's spike protein, which may make it more transmissible and more resistant to vaccines.
The study also found the variant displayed a roughly three-fold increase in resistance to neutralizing antibodies elicited by the Covid-19 vaccine developed by Pfizer-BioNTech, as well as a 2.3-fold increase in resistance to antibodies elicited by the Moderna vaccine. A separate study, published in MedRxiv, found the lambda variant had a 3.05-fold increase in resistance to antibodies elicited by the CoronaVac vaccine.
Earlier this week, a Houston Methodist Hospital reported its first confirmed case of the lambda variant, ABC News reports. However, according to the hospital, the vast majority (85%) of the 185 Covid-19 cases that it reported as of Monday stemmed from the delta variant—the variant experts say remains the most significant Covid-19 threat in the United States.
"I don't think there's sufficient evidence at this point that we should be more concerned about lambda than delta," Wesley Long, medical director of diagnostic microbiology at Houston Methodist, said. "I still think delta is the primary concern for us."
According to Long, there is "a lot more evidence that we have that delta is much more contagious, the viral loads are much higher."
Experts also cited lambda's relatively slow spread throughout the country in comparison to delta. Since the variant emerged in the United States months ago, it has accounted for fewer than 700 Covid-19 cases, the Washington Post reports.
"What's going on here in the U.S. is lambda is competing against the delta variant. And I think it's losing the competition," Peter Stoilov, an associate professor of biochemistry at West Virginia University, said. "The question is how competitive this variant is going to be. I don't see it spreading anywhere near as fast as the delta."
Separately, Nathaniel Landau, a microbiologist at New York University, said lambda "doesn't really make the situation any worse. It's just more of the same."
Moreover, researchers have found that at least two of the Covid-19 vaccines authorized for use in the United States remain very effective against the lambda variant.
For instance, another preprint paper in BioRxiv found that while the lambda variant showed a slight resistance to the Pfizer-BioNTech and Moderna vaccines, the vaccines still produced a sufficient antibody response to neutralize the variant. "The vaccines induce such good antibodies that even if the virus is a little bit resistant, they are still quite sufficient to kill the virus," Landau said.
The study did find, however, that Johnson & Johnson's (J&J) vaccine did not provide as robust an antibody response against either the lambda or delta variants. However, Landau noted J&J's vaccine offers other benefits, such as its ability to help T cells fight off infection.
"There's no reason to think that the T cell response isn't as good," Landau said. "It would still be there to block variant viruses."
Ultimately, Long said the best defense against any coronavirus variant is a vaccine, and that people have a choice to either get vaccinated or get infected. "No matter what Greek letter comes along next, the vaccine is really our best defense," Long said. "If anybody thinks they can hunker down and never get this virus, I think that's a fantasy." (Frazier, Axios, 7/20; Lenthang, ABC News, 7/20; Hawkins, Washington Post, 7/20)
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