Steve September 13, 2021

13 September 2021

What was claimed

The Mu variant of Covid-19 is “immune to vaccines”.

Our verdict

The Mu variant possesses a number of mutations, some of which may make it more likely to evade the immune system. However, it is incorrect to say that the evidence so far suggests the variant is entirely “immune” to vaccines, or that they won’t work at all.

A COVID variant that is immune to vaccines has reached Britain

The Daily Express print edition reported on 8 September that there have been 53 cases of the Mu variant of Covid-19, and described it as a “Covid variant that is immune to vaccines”. While the variant possesses mutations that may make it more likely to be able to evade vaccines, the evidence so far does not suggest that the vaccines won’t work against it at all.

The Mu variant, which has particularly affected Colombia, has been designated a variant under investigation by the World Health Organisation (WHO), and Public Health England (PHE). 

As we have written before, a variant under investigation is a variant that could have concerning properties with regard to transmission, ability to evade the immune system or vaccines, or ability to make people more unwell than previous variants. A variant under investigation may be upgraded to become a variant of concern if it then actually demonstrates these properties.  

The Mu variant has shown a number of important mutations. One such mutation is E484K, which is also present in the Beta variant and is associated with potentially being able to evade antibodies or ‘dodge’ the immune systems of individuals who have been vaccinated or previously had Covid-19. When it was first identified, there were also concerns that the Beta variant may be able to ‘dodge’ the immune system.

The other mutations that have been identified in Mu variants include R346K,  Y144T and P681H, amongst others. Mutations R346K and Y144T are newer and not yet fully understood, while P681H (which was also reported in the Alpha variant) may contribute to faster transmission, although this is yet to be confirmed.

Dr Vinod Balasubramaniam, a virologist at the Jeffrey Cheah School of Medicine & Health Sciences at Monash University Malaysia, told the Science Media Centre in Australia there is currently “only limited information” on whether the Mu variant can “evade pre-existing immunity”, citing a study from Rome that suggested the Pfizer/BioNTech vaccine was less effective against Mu than other variants.

However, he added: “Despite this, the study still considered the protection offered against Mu by the vaccine to be robust. 

“Really, we don’t yet know whether Mu’s mutations will translate into increased infection and disease”.

Dr Alessandro Carabelli, research lead at COG-UK mutational analysis working group—a part of the UKs ​​national pathogen genomics network—told Full Fact that while antibodies have shown lower activity against Mu in lab studies, there is no evidence that the variant is “escaping” the vaccines “in the field”. 

He added that Mu is still being “outcompeted” by the “highly transmissible” Delta variant in many places. 

According to the most recent PHE update, up to 8 September there have been 53 cases of Mu variant in the UK, with no associated deaths (from data up as of 30 August).

The Daily Express online has published other articles about the Mu variant, where they have more accurately reflected what is known about it. One article states: “There have been concerns the variant could evade vaccine protection, however further research is needed to confirm this”. 

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