According to the Center for Disease Control and Prevention, about 83% of COVID-19 cases in the United States are delta variant, with the vast majority of hospitalizations occurring among unvaccinated individuals.
The lambda variant, in contrast, has been identified in fewer than 700 cases in the United States. However, the World Health Organization in June described lambda as an "interesting variant," meaning that it has genetic changes that affect the characteristics of the virus and has led to significant spread in COVID-19 communities or clusters in many countries.
Dr. S. Wesley Long, medical director of diagnostic biology at Houston Methodist, where the case was identified, said that although lambda has some mutations similar to the other variants of interest, it does not appear to have the same transmissibility as delta.
"I know there's a lot of interest in lambda, but I think people should focus on delta," Long said. "The most important thing, regardless of the variant, is that our best defense against all of these variants is vaccination."
What is the lambda variant and how is it different from the delta variant?
The lambda variant is a particular strain of COVID-19 with specific mutations. It is one of several variants identified by WHO as variants of concern. Since the outbreak was first detected in late 2019 in central China, many other variants have emerged.
"The natural trajectory of viruses is such that they tend to mutate, and whenever we have a significant mutation that changes the virus ... we get a new variant," said Abhijit Duggal, M.D., staff physician in the intensive care unit and director of intensive care research in the Cleveland Clinic's medical intensive care unit.
"Some mutations in lambda occur in its spike protein, which is the part of the virus that helps it penetrate cells in the human body, and that's where vaccines are targeted.
The mutations that occur there and in other parts of lambda are similar to those that occur in such worrisome variants as alpha and gamma, Long said. But even gamma, which has never been as prevalent in the U.S. as alpha or delta, has more mutations than lambda, Long said.
Duggal said the lambda variant doesn't yet have much to worry about for it to become the dominant variant in the U.S., but that "watchful waiting and caution is the most important thing right now."
Where was the lambda variant first identified?
The lambda variant was first identified in Peru in December 2020. Since April, the lambda variant has been identified in more than 80% of sequencing cases in the country.
In June, WHO said it had identified the lambda variant in 29 countries. Argentina and Chile have also seen an increase in lambda cases, according to WHO.
Globally, however, the variant has not received the same prevalence as the delta variant. Lambda may have become so widespread in parts of South America primarily because of the "founder effect," Long said, with a few cases where the variant first becomes established in a densely populated and geographically limited area and eventually becomes a major factor in local spread.
Long compared lambda to the gamma variant, which was first detected in Brazil and spread in a similar manner.
Are COVID-19 vaccines effective against the lambda variant?
Studies have shown that vaccines currently licensed for use in the U.S. are highly effective in preventing severe COVID-19 and death in various variants.
Duggal said that while there is no reason to believe the vaccines will be ineffective against the lambda variant, more data is needed to know exactly how effective they will be. Efficacy may decrease slightly, but hospitalizations can still be largely prevented in variant cases with vaccination, he said.
"Nothing in this world is 100 percent": people fully vaccinated against COVID-19 can get infected, but severe illness is rare.
But a new study published online Tuesday shows that Johnson & Johnson's vaccine is not as effective at preventing symptomatic disease when it comes to delta and lambda variants. The study has not yet been peer-reviewed or published in a journal, but it is consistent with AstraZeneca's vaccine studies, which concluded that one dose of the vaccine was 33% effective against symptomatic delta variant disease.
Vaccines produced by Pfizer-BioNTech and Moderna showed similar levels of efficacy against several variants of concern.
Vaccination remains the most important factor in stopping the deadly effects of the virus and slowing the emergence of new variants, Long said.
Mutations occur in the coronavirus as it spreads from person to person. Vaccination can help prevent symptomatic disease and slow the spread in highly vaccinated communities, which can prevent mutations and the emergence of new variants, Duggal added.
Image credit via getty images
A man wears an American flag facemask outside Los Angeles on July 19, 2021, on the second day of an indoor facemask mandate in Los Angeles County due to a spike in coronavirus cases. On July 18, the U.S. Surgeon General defended the renewal of the mask mandate in Los Angeles County, stating that other districts could follow suit, adding that he was "deeply concerned" about the Covid-19 forecast for the fall. Los Angeles County has reported another 1,233 Covid-19 cases, and this is the 11th consecutive day above 1,000.