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HomeHealth TopicVaccines

What Is the Lambda Variant, and Does It Cause Vaccine-Resistant COVID-19?

Patricia Pinto-Garcia, MD, MPHKatie E. Golden, MD
Published on August 24, 2021

Key takeaways:

  • The Lambda variant is a “variant of interest” that has been spreading in South America and is now in the U.S.

  • There is some limited data showing that the Lambda variant could be more infectious than the original Alpha variant and resistant to vaccines.

  • The Lambda variant has caused very few cases of COVID illness in the U.S.

A sick person holding a blister pack.
Paul Bradbury/OJO Images via Getty Images

This summer, COVID-19 news has been dominated by the Delta variant, which quickly became the dominant variant in the United States. But in the last few weeks, attention has shifted to a new variant called the Lambda variant, also known as C.37. 

How does the Lambda variant compare with other COVID-19 variants? Learn more about this variant and how it may impact current COVID outbreaks. 

What is the Lambda variant?

The Lambda variant is a type of COVID-19 virus that was first identified in South America. The Lambda variant is different from other COVID variants because it has several mutations on its spike protein. Initial data from Japanese and Chilean research teams, which is not yet verified or published, show that these mutations may give the Lambda variant similar properties to the Delta variant — that is, these mutations could make the Lambda variant more infectious than the original Alpha variant. What’s more, these mutations could make the Lambda variant more resistant to vaccines. 

How do new COVID-19 variants happen?

Variants happen when a virus mutates. Viruses reproduce and multiply quickly, and each round of replication can produce new mutations. Some mutations have no effect on viruses but others can make the virus stronger and better able to survive. Stronger viruses can have higher infectivity rates, allowing them to infect more people. They can also become resistant to vaccines and the immune system response — this is called immune escape

Although many COVID-19 variants have been discovered, not all of them are concerning. There are currently more than a dozen variants of COVID-19 circulating worldwide, and the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) are tracking all of them. The WHO and CDC keep close watch on variants they deem “variants of concern” and “variants of interest.” 

A variant of interest is an emerging variant that is contributing to COVID cases. It becomes escalated to a variant of concern when it makes vaccines less effective and has the potential to cause more serious disease. A variant’s classification can change over time as more information becomes available.

When was the Lambda variant discovered?

The Lambda variant was first identified in Peru in August 2020. It has spread throughout South America and is now present in 29 countries, including the U.S. The variant has been found in 44 states but accounts for a small percentage of cases reported in the U.S.  

The WHO promoted the Lambda variant to a “variant of interest” in June 2021. The CDC does not consider Lambda a variant of interest or concern. 

Is COVID-19 from the Lambda variant different from COVID-19 caused by other variants?

The symptoms of COVID-19 caused by the Lambda variant are the same as symptoms caused by other variants. 

So far, the Lambda variant is only a “variant of interest” according to the WHO. This means that the variant has mutations that could increase disease severity. But this evidence is based on laboratory studies, and we don’t have enough evidence to show that it does cause more severe illness or increases the risk of hospitalization. If either of these things happen, the WHO and CDC could change the Lambda variant to a “variant of concern.” 

Is the COVID-19 vaccine effective against the Lambda variant?

There is some data that shows that vaccines could be less effective against the Lambda variant. However, this data is from a study done in the lab, and such data does not always correlate with what happens in real life. This data has not been peer reviewed or published yet either. 

The presence of this new variant does not change the fact that the COVID vaccine is safe and effective. 

What can you do to lower your risk of exposure to the Lambda variant?

Fortunately, the Lambda variant is not that common in the U.S. In fact, 93% of COVID cases are due to the Delta variant, while less than 1% are due to the Lambda variant. Scientists also think that Lambda doesn’t spread as quickly, and that’s why Delta remains the main variant in the U.S. 

That means the usual methods of prevention are enough to protect yourself from the Lambda variant. Remember to:

  • Isolate if you are sick with COVID symptoms and get tested if necessary.

  • Stay away from others who are sick with COVID symptoms.

  • Wash your hands often.

  • Wear a mask.

  • Get vaccinated.

The bottom line

The Lambda variant is a “variant of interest” because of its potential to be more infectious and show vaccine resistance. Fortunately, this data has only been shown in the lab and not in humans. The variant has not been spreading very rapidly in the U.S. The best way to protect yourself against the Lambda variant is to get vaccinated against COVID-19.


Acevedo, M. L., et al. (2022). Differential neutralizing antibody responses elicited by CoronaVac and BNT162b2 against SARS-CoV-2 Lambda in Chile. Nature Microbiology.

Centers for Disease Control and Prevention. (2022). Ensuring COVID-19 vaccine safety in the US.

View All References (7)

Centers for Disease Control and Prevention. (2022). SARS-CoV-2 variant classifications and definitions.

Fung, K. (2021). The Lambda COVID variant: What WHO, CDC have said. Newsweek.

Harvey, W. T., et al. (2021). SARS-CoV-2 variants, spike mutations and immune escape. Nature Reviews Microbiology.

Hogan, A. (2021). Watch: How — and why — coronaviruses mutate. Stat.

Kimura, I., et al. (2022). The SARS-CoV-2 Lambda variant exhibits enhanced infectivity and immune resistance. Cell Reports.

Tada, T., et al. (2022). Neutralization of SARS-COV-2 variants by mRNA and adenoviral vector vaccine-elicited antibodies. Frontiers in Immunology.

World Health Organization. (2022). Tracking SARS-CoV-2 variants.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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