Is the Mu COVID Variant Resistant to Vaccines?

The Mu COVID-19 variant—first detected in Colombia at the beginning of this year—was recently listed as a "Variant of Interest" (VOI) by the World Health Organization (WHO.)

Some media reports have raised concerns that the variant may be more capable of evading our immune defences than other versions of the SARS-CoV-2 virus. But is it more resistant to COVID-19 vaccines?

According to the WHO's definition, a VOI exhibits "genetic changes that are predicted or known to affect virus characteristics such as transmissibility, disease severity, immune escape, diagnostic or therapeutic escape."

In addition, a VOI has been identified to cause "significant community transmission or multiple COVID-19 clusters, in multiple countries with increasing relative prevalence alongside increasing number of cases over time, or other apparent epidemiological impacts to suggest an emerging risk to global public health."

Mu has been detected in at least 40 countries, but is thought to only account for less than one percent of current new infections globally.

While there have been significant outbreaks in some countries, such as Colombia, in many regions, Mu appears to have been outmuscled by the highly transmissible Delta variant.

In the U.S., for example, the Delta variant now represents more than 99 percent of new cases, with Mu only accounting for around 0.1 percent, according to the Centers for Disease Control and Prevention's COVID tracker.

Nevertheless, the Mu variant has garnered significant interest because it contains some potentially concerning mutations.

Among these are the mutations E484K and K417N, which have been associated with the virus being able to evade antibodies against the SARS-CoV-2 virus, which causes COVID-19.

Mu also has several other mutations, the consequences of which are currently unknown, Luke O'Neil, a professor of biochemistry at Trinity College Dublin in Northern Ireland wrote in The Conversation.

While these mutations may mean that Mu has the potential to evade the body's immune response to an extent, the limited evidence that is available indicates that vaccines will likely not be rendered completely ineffective against the variant.

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 that there is relatively little information on whether Mu can evade "pre-existing" immunity.

Balasubramaniam cited a study from Rome, the results of which indicated that the Pfizer-BioNTech vaccines was less effective against Mu than other variants.

But despite this, he said: "The study still considered the protection offered against Mu by the vaccine to be robust."

The scientist also noted that more research needs to be conducted to better understand the true characteristics of Mu.

Dr. Alessandro Carabelli, a senior researcher with the COVID-19 Genomics UK Consortium, told Full Fact that while some lab research has demonstrated reduced antibody responses against the Mu variant, there is still a lack of evidence to show that it is "escaping" vaccines "in the field."

A dose of the Pfizer-BioNtech vaccine
An individual receives a dose of the Pfizer-BioNtech vaccine in Derby, central England on September 20, 2021. Is the Mu SARS-CoV-2 variant resistant to vaccines?