What to know about the lambda variant

The lambda variant of the novel coronavirus has received a flurry of news coverage since it was added to the World Health Organization variant watch list in June. Lambda swept through several South American countries earlier this year and has been detected the United States, including this week at a hospital in Houston.

Infectious-disease experts aren’t sounding any alarms about lambda yet. Its progress here has been slow, with fewer than 700 cases identified since it emerged in the country months ago. Moreover, experts say the threat from lambda is insignificant next to the highly transmissible delta variant, which is spreading rapidly among unvaccinated people.

Still, scientists are studying the lambda variant, which has shown signs of being more transmissible than milder versions of the coronavirus. Here’s what you need to know about it.

What exactly is the lambda variant?

The lambda variant is an emerging version of the novel coronavirus that was first detected in Peru in August 2020. It now accounts for the vast majority of new cases in that country.

At least 29 countries have reported lambda recent months. Chile, Argentina and Ecuador have seen the most significant increases outside of Peru, according to the WHO.

The spread of lambda in South America led the WHO to designate it a “variant of interest” on June 14. That means scientists have identified genetic changes that could make it more dangerous than earlier versions of the virus.

According to experts, lambda has some of the same types of mutations observed in the alpha, beta and gamma variants that may increase transmission. It also has a mutation similar to one found in delta that may allow it to more easily infect lung cells.

But the WHO designation is less severe than “variant of concern,” a label the agency reserves for variants that have been shown more definitively to spread faster, make people sicker, or evade vaccines or treatments.

How big of a concern is it in the U.S.?

Experts are generally confident that the lambda variant won’t erupt in the U.S. the way it did in Peru.

Lambda has quietly circulated for months in the United States without taking off. By comparison, the delta variant was first identified in the United States in March and now accounts for more than 80 percent of new infections over the past two weeks, according to the Centers for Disease Control and Prevention.

“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,” said Peter Stoilov, an associate professor of biochemistry at West Virginia University.

“It doesn’t really make the situation any worse,” said Nathaniel Landau, a microbiologist at New York University. “It’s just more of the same.”

How effective are vaccines against it?

Even if the lambda variant were to surge in the United States, there’s good news: two of the three federally approved coronavirus vaccines appear to work well against it.

A paper posted Monday by Mr. Landau and other researchers at NYU found that the Pfizer and Moderna vaccines had no problem neutralizing lambda. The variant showed a slight resistance to the two mRNA vaccines, but the shots were still highly effective, according to the study, which has not been peer reviewed.

The Johnson & Johnson vaccine doesn’t offer the same defenses against lambda or delta, the researchers found.

Still, Mr. Landau was quick to point out that the Johnson & Johnson vaccine offered other benefits, including its ability to help the body’s T cells fight infection.