You are currently viewing MU Coronavirus: The More “Vaccine Resistant” Variant

September 15, 2021

by Mary Joy Saludo


As stated in Philstar , SARS-CoV, just like any other virus, will mutate over time. It may not have much change on the properties of the virus, however, it can affect its resistance to medication or vaccines, how severe it is, or how quickly it can spread.

According to sources from National Geographic,  as of September 10 of this year, a new variant has been found in 42 countries called the Mu (B.1.621) variant. As of then, the variant is still classified as a variant of interest (VOI) and is currently being monitored by the World Health Organization (WHO). It is the 12th of the noteworthy variants to date including the variants of concern (VOC) such as the Alpha, Beta, Gamma, and especially the Delta variant that is currently dominant in the United States as well as here in the Philippines.

The “Mu” Variant

The variant was first detected in January of 2021 in Columbia where it quickly became a dominant strain. The Mu variant is responsible for about 39% of the COVID-19 cases in the country.

Several studies and observations have been made about the variant but they are not yet final and some were not yet peer-reviewed. For instance, according to Maria Rosario Vergeire to CNN Philippines on September 3,  there are initial studies that indicate that this easily transmissible variant may result in more severe COVID-19 infections. While preliminary research shows that it is less transmitted as easily than the deadly Delta variant, there are recent studies that suggest that the variant is more resistant to neutralization by sera from those who were recovering from COVID or vaccinated. Kei Sato and his colleagues also conducted a study to show how much more resistant the Mu variant is compared to other variants of interest or concern in a News Medical Life Sciences article. This may be because the variant’s harbored spike mutations like E484K and N501Y have made variants more resistant to the antibodies from mRNA vaccines. And according to unpublished research that utilized epidemiological models, Mu is at least twice as transmissible as the original SARS-CoV-2 being as it is responsible for the wave of COVID deaths in Bogotá, Colombia, in May 2021.

Further study will be needed to confirm and understand its clinical and phenotypic characteristics. After all, as stated in National Geographic,  despite its dominant strain in Columbia, it has not spread in the U.S. significantly and the prevalence of the variant has steadily declined. The U.S., similar to the Philippines, is more dominated by the Delta virus.

Number of cases in the Philippines

Dr. Cynthia Saloma, executive director at the Philippine Genome Center in an article by ABS-CBN News says, no cases for the Mu variant have been detected in the country for now. At the moment, the Delta variant is more of a problem.

According to Saloma, the “best defense” will be the vaccination and health standards. She further stated that they will always be on standby and observe the entry of the variants within the borders. In addition, the variants including the 4 other variants of interest (Eta, Iota, Kappa, and Lambda) and variants of concern (Alpha, Beta, Gamma, and Delta) will be monitored and assessed closely by WHO as stated by Rappler.  They’ll be further studied for their pathogenicity, immune response resistance, and enhanced transmission.