Lambda Vs. Delta Variants—What to Know As New Forms of COVID Spread in U.S.

A hospital in Houston has reported a case of the Lambda variant of COVID-19 this week as the U.S. continues to see a marked rise in coronavirus infections.

More than 80 percent of all COVID cases across the country are thought to involve the Delta variant, according to the U.S. Centers for Disease Control and Prevention (CDC).

The Lambda variant has attracted attention in recent weeks, however, particularly because the World Health Organization declared it a "variant of interest" on June 14.

This designation means it has genetic changes that can affect how transmissible it is and the severity of the illness it causes, among other factors.

The Lambda variant, also known as C.37, was first documented last December in Peru, according to the WHO.

Just under 700 cases have been identified in the U.S., according to the website

However, experts have told Newsweek that little is known about Lambda, including how resistant it is to vaccines and exactly how much risk it poses.

Dr Julian Tang, professor of respiratory sciences at the University of Leicester in the U.K., thinks that Delta is a more serious variant than Lambda, based on current data.

He told Newsweek there was no real-world large population data yet on how the Lambda variant might resist vaccines, but did point to two non-peer-reviewed studies suggesting it may possess similar vaccine-resistance properties as the Alpha and Gamma variants.

Tang added that the Delta variant, by comparison, showed "a much larger vaccine-escape capability"—a reduction in the overall effectiveness of existing vaccines against it.

John P. Moore, professor of microbiology and immunology at Cornell University's Weill Cornell medical school in New York, also said there was "not enough information in the scientific literature" to assess the risks posed by Lambda.

He added that Delta posed a "clear and present danger worldwide," however, describing it as "the most transmissible [variant] we have seen so far."

What is clear is that more variants will emerge if people remain susceptible to catching COVID-19 in the first place, said Jagpreet Chhatwal, an assistant professor at Harvard Medical School.

Dr Sarah Fortune, professor of immunology and infectious diseases at the Harvard TH Chan School of Public Health, told Newsweek there was still a "huge amount of virus in the world" and many people who can still be infected.

"Consequently, we are going to see ongoing viral evolution—where the virus is going to continue to spin off more transmissible variants.

"The single most important thing that we can do is continue to rapidly push vaccine coverage to try to get the global reservoir of virus down, so basically the virus has fewer shots on goal."

The Pfizer vaccine is 96 percent effective at preventing hospitalization in Delta COVID patients who have had two doses, according to analysis by Public Health England in the U.K. It is 94 percent effective in preventing severe illness, according to an Israeli study.

Pedestrians walking
Pedestrians wearing face masks in Huntington Beach, California, seen in April 2020. More than 80 percent of U.S. cases of COVID-19 at the moment involve the Delta variant, according to the CDC. Apu Gomes/AFP/Getty