The latest report from the UK government case data, published 26 November 2021, confirms that there have been no new cases of the Lambda variant of interest within the last week.


The variant, also known as C.37, was first detected in Peru, in August 2020. Peru has had no new cases of Lambda in the last month.

Cases attributed to the Lambda COVID variant have been declining, according to data from the GISAID COVID tracking initiative. In the last four weeks, there have been nine new cases globally that were associated with Lambda. Of these, three were in Chile and six in Argentina.

However, the WHO and experts from around the world will continue to monitor numbers of the Lambda strain, keeping it on the list of classified variants of interest.

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Researchers at the NYU Grossman School of Medicine have tested the effectiveness of MRNA coronavirus vaccines, like Pfizer and Moderna, against the Lambda variant.

According to their results – which have yet to be peer-reviewed – there was a "partial resistance to neutralisation”, however this "is not likely to cause a significant loss of protection against infection" in vaccinated individuals.

But their analysis of the spike proteins on the SARS-CoV-2 Lambda variant showed a two-fold increase in infectivity, which scientists say is due to a particular mutation on the virus called the L452Q mutation.

A map of occurrences of the C.37 Lambda variant of coronavirus, as of 29 September 2021 ©
A map of occurrences of the C.37 Lambda variant of coronavirus, as of 29 September 2021 ©

Lambda was classified as a variant of interest at the global level by the World Health Organization (WHO) on 15 June 2021.

As a variant of interest, the WHO considers Lambda to have mutations with established, or suspected, implications for its transmissibility and severity, and has been detected in multiple countries.

Dr Maria Van Kerkhove, the WHO's technical lead on COVID-19, said that the organisation is tracking the strain to see if it should be classified as a variant of concern. This would happen if the strain "demonstrated properties of increased transmissibility", or "if it has increased severity," she said.

The Lambda variant will only be designated a variant of concern if it is deemed to either: increase the transmissibility of the virus; show a detrimental change in its epidemiology; increase in virulence; change the disease presentation/symptoms; or shows decrease in the effectiveness of testing, treatment, and prevention measures such as vaccinations.

How many cases of the Lambda variant have been detected in the UK?

As of 26 November 2021, there have been eight confirmed cases of the C.37 variant in the UK.

The majority of these are linked to overseas travel, according to a PHE spokesperson. There have been no cases reported in the UK within the last four weeks.

“There is currently limited evidence available about this variant," Dr Alicia Demirjian, COVID Incident Director at Public Health England (PHE), told BBC Science Focus magazine.

"PHE, together with academic partners, is undertaking investigations to better understand the impact of the mutations on the behaviour of the virus. We are closely monitoring the situation in those countries where this variant is prevalent and where cases are detected in the UK, we are testing contacts and will undertake targeted case finding if required.”

A report by PHE on the variants of concern or under investigation in the UK shows that the Delta variant continues to be the prominent strain in the UK. In the week leading up to 17 November 2021, there were 67,070 new cases of the Delta variant.

Will vaccines still work against the Lambda variant?

In a pre-print paper that has not yet been peer-reviewed, researchers found that mRNA vaccines are effective against the Lambda variant. Both the Pfizer and the Moderna coronavirus vaccines used in the UK are mRNA jabs, meaning they contain genetic material that instructs the body's cells to produce coronavirus spikes, which then provokes an immune response.

The results of this paper suggest that vaccines in current use will remain protective against the Lambda variant.

However, in another pre-print paper, Lambda was found to have mutations that had "the ability to escape from neutralising antibodies elicited by CoronaVac”. CoronaVac is a vaccine being used in several Asian countries, and works by administering an inactive version of the SARS-CoV-2 virus, which then triggers an immune response.

Researchers have stressed that further studies are required to validate the effectiveness of vaccines.

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Is the Lambda variant more transmissible?

While it is not known yet whether this new variant is more transmissible, scientists say the Lambda strain does carry a number of mutations that could potentially lead to increased transmissibility or increased resistance to the antibodies provided by a COVID-19 vaccination or prior exposure to the virus.

One of the mutations identified in the Lambda strain is referred to by scientists as T859N, and has been found in the so-called 'Iota' variant currently spreading in New York City.

Another mutation, at L452Q, is reported as being "similar to the mutation reported in the Delta and Epsilon variants" which is believed to affect its susceptibility to antibodies.

However, it's important to note that research on this specific variant is all in early stages.

As there is currently little evidence to show exactly how the Lambda variant is different to the other strains, scientists say that further, more robust studies, are needed before we can understand the full extent of the strain's effect.

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What are the symptoms of the Lambda variant?

At present, there is nothing to suggest that the symptoms of infection with the new C.37, or Lambda, variant are different to other coronavirus strains.

The main symptoms of COVID-19, according to the NHS, are:

  • a high temperature – this means you feel hot to touch on your chest or back (you do not need to measure your temperature)
  • a new, continuous cough – this means coughing a lot for more than an hour, or three or more coughing episodes in 24 hours (if you usually have a cough, it may be worse than usual)
  • a loss or change to your sense of smell or taste – this means you've noticed you cannot smell or taste anything, or things smell or taste different to normal

The NHS say that most people who have symptoms of COVID-19 will have at least one of the above.

What other variants of concern have been identified in the UK?

It is common for viruses to mutate when they replicate. Few of these small, genetic changes lead to a more harmful infection.

As of 26 November 2021, there are four strains considered to be ‘of concern’ by PHE, including the Delta and Alpha variants.


The PHE are monitoring a total of 15 variants.

About our expert, Dr Alicia Demirjian

Dr Demirjian is the COVID Incident Director at Public Health England (PHE). She is a clinician and epidemiologist, and trained at Boston Children's Hospital in general paediatrics and paediatric infectious diseases. Demirjian works as a consultant at Evelina London Children’s Hospital alongside her work with PHE.


Amy ArthurEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.